bluuebunny/crossref_metadata_2025 huggingface dataset:
Behaviour of male pine sawflies, Neodiprion sertifer, released downwind from pheromone sources
Authors: Östrand Fredrik , Anderbrant Olle , Jönsson Peter
Published: October 2003

This study investigated the behaviour of male European pine sawflies, Neodiprion sertifer Geoffroy (Hym., Diprionidae), that were released and observed downwind from pheromone traps baited with 100 μg of the sex pheromone, (2S,3S,7S)‐3,7‐dimethyl‐2‐pentadecyl acetate. Releases were done at three distances; either at 5 m from one trap, or at 50 or 200 m from five traps, placed in a line perpendicular to the current wind direction. As control, males were released identically but without any pheromone source present. The behaviour of the males prior to take‐off was studied. A total of 1729 males were released, and 80% of them took flight. Males took off significantly faster in the presence of pheromone. Grooming was significantly more frequent in presence of pheromone compared with control. In all pheromone experiments significantly more males displayed grooming, wing fanning and take‐off towards the wind compared with the control. Weather data was simultaneously collected at the study site. Wing fanning was negatively correlated with wind speed. Grooming was not influenced by wind speed. Reduced levels of incoming short‐wave radiation lowered the take‐off frequency significantly. Pheromone‐induced behaviour in diprionids seems to be less distinct than in other insects, e.g., Lepidoptera.
Specificity of chemical cues used by a specialist egg parasitoid during host location
Authors: Meiners Torsten , Westerhaus Christine , Hilker Monika
Published: October 2003

Plant synomones and host kairomones are known to guide the egg parasitoid Oomyzus gallerucae to its specific host, the elm leaf beetle Xanthogaleruca luteola (=Pyrrhalta) (Muller) feeding upon elm leaves (Ulmus spp.). In this study, we investigated whether the activities of these plant synomones and kairomones are specific for the plant and herbivore species, respectively. Olfactometer and contact bioassays were used. In habitat location, O. gallerucae (Fonscolombe) is known to use synomones from Ulmus minor (Miller) that are induced by egg depositions of X. luteola. The attractiveness of such induced volatiles was shown to be specific both for the Ulmus species and the herbivore species depositing eggs. Neither leaves of U. glabra Hudson (=U. montana) carrying eggs of X. luteola nor leaves of U. minor (=U. campestris=U. procera) carrying eggs of the chrysomelid species Galeruca tanaceti L. emitted attractive synomones. O. gallerucae is also known to be attracted by volatile kairomones from faeces of X. luteola feeding on U. minor and to show prolonged antennal drumming when contacting substrates contaminated with these faeces. The kairomonal activity of the faeces was proved to be independent of the Ulmus species, since also faeces from elm leaf beetles feeding upon U. glabra emitted attractive volatiles. However, the faecal kairomones were specific for the herbivorous species, since faeces from a lepidopteran larva (Opisthograptis luteolata L.) feeding upon elm hardly elicited any antennal drumming in O. gallerucae. The egg parasitoid studied is known to recognize host eggs of X. luteola by contact kairomones extractable from the egg shell. O. gallerucae clearly differentiated between host eggs and eggs of another closely related chrysomelid species, Galerucella lineola L., as was shown by comparing duration of antennal drumming on host eggs and eggs of G. lineola.
Rearing of Prays citri on callus derived from lemon stigma and style culture
Authors: Carimi Francesco , Caleca Virgilio , Mineo Giovanni , De Pasquale Fabio , Crescimanno Francesco Giulio
Published: October 2003

A new method for rearing the citrus flower moth (Prays citri Mill.) (Lepidoptera, Yponomeutidae) on lemon [Citrus limon (L.) Burm.] callus is reported. In the present research callus (an undifferentiated mass of plant cells that can be grown under sterile conditions on an artificial medium in vitro) was induced from lemon stigma and style explants cultured on Murashige and Skoog (MS) medium supplemented with 500 mg l−1 malt extract, 13.3 μM 6‐benzylaminopurine, and 146 mM sucrose. Also somatic embryogenesis and plant regeneration were obtained from the cultures of styles and stigmas of lemon. Adults were obtained from larvae on infested flowers collected in the field. Different oviposition substrates were used: white oval pearls (WOP), black oval pearls (BOP), rooted shoots (RS) of lemon obtained in vitro, and artificial flowers containing lemon callus (AF). Larvae were reared on lemon callus. Adults oviposited on RS, on WOP, and on AF. BOP were rejected as oviposition substrates. The flower moth reared on callus oviposited fertile eggs. In our tests P. citri completed three generations on callus or on callus plus shoots. In the latter case the larvae preferred callus and fed on shoots only after callus was completely eaten. The life cycle on callus at 23 ± 1 °C lasted about 21 days. There were significant differences between oviposition substrates for what concerns the number of eggs laid. It was observed that females generally preferred WOP (about 25 eggs/female) to AF (about 20 eggs/female) or RS (about 12 eggs/female) as oviposition substrate. Nevertheless the percentage of eggs that developed into adults was higher when AF sealed with stretched Parafilm were used (about 70% of eggs developed into adults). The method of rearing P. citri with AF was labour‐saving and the feeding substrate (callus) had less tendency to become mouldy or decompose than when WOP and RS were used. Since such a diet is available for the insect all year round and callus can be produced in unlimited quantity, it could be possible to obtain a mass production of this moth.
The feeding behavior of Trichogramma brassicae: new evidence for selective ingestion of solid food
Authors: Wu Z.X. , Cohen A.C. , Nordlund Donald A.
Published: October 2003

A descriptive study of the feeding behavior and structures of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was conducted. Based on direct observational and biochemical evidence, larvae feed predominantly on particulate materials, starting ca. 25 h post‐oviposition. Feeding lasted for ca. 9 h, at 25±1 °C. During this feeding period the shape of the larvae changed from vermiform to pyriform and then to sacciform, resulting in a ca. 40‐fold increase in body size. Larvae used elaborate feeding behaviors as they pulled solid food particles to their oral opening, broke small particles from larger ones, and took the particles into the stomodaeum, which is a powerful pump. In the stomodaeum, peristaltic movement further macerated the particles, which eventually passed through the cardiac valve into the midgut. As indicated by changes in fluorescently labeled casein, digestive enzymes aid in the extra‐oral chemical digestion of food. The contents of the gut, during and shortly after feeding, were almost entirely closely packed solid particles. The behavioral activity of feeding larvae centered almost exclusively on processing and ingesting solid food particles. The rapid larval growth is much more plausibly explained by their feeding on the highly concentrated nutrients found in solid foods, rather than the extensive concentration required if dilute liquids were the principal source of nutrients. The implications of these findings for the development of practical artificial diets are discussed.
Relationships between the occurrence of misshapen fruit on late‐season strawberry in the United Kingdom and infestation by insects, particularly the European tarnished plant bug, Lygus rugulipennis
Authors: Easterbrook M.A.
Published: October 2003

In experiments in which the European tarnished plant bug, Lygus rugulipennis, was caged on the developing flowers or young fruits of strawberry, the insects caused malformation of the fruits. Another species of capsid, Plagiognathus chrysanthemi, caused similar damage; this species is less numerous than L. rugulipennis on late‐season crops of strawberry in UK. Other insects which sometimes occur in large numbers in the flowers of late‐season strawberry, i.e. various species of thrips and pollen beetles, did not cause fruit malformation in caging experiments, though thrips sometimes caused discoloration of the fruit. In field experiments where numbers of L. rugulipennis were reduced by the use of insecticides, the amount of misshapen fruit was reduced greatly compared to untreated plots. Correlations between the numbers of L. rugulipennis present at the early stages of fruit development and damage scores for fruit deformity were highly significant. This capsid is likely to be the major cause of fruit malformation in late‐season crops of strawberry in the UK.
Geographical variation in female sex pheromones of the rice leaffolder moth, Cnaphalocrocis medinalis: identification of pheromone components in Japan
Authors: Kawazu Kei , Hasegawa Jun‐ichi , Honda Hiroshi , Ishikawa Yukio , Wakamura Sadao , Sugie Hajime , Kamiwada Hidemi , Kamimuro Takeshi , Yoshiyasu Yukata , Tatsuki Sadahiro
Published: October 2003

Sex pheromone components of the Japanese rice leaffolder moth, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) were identified from ovipositor extracts of virgin females as (Z)‐11‐octadecenal, (Z)‐13‐octadecenal, (Z)‐11‐octadecen‐1‐ol and (Z)‐13‐octadecen‐1‐ol at a ratio of 11:100:24:36 by GC‐EAD, GC, GC‐MS. The total amount was estimated to be ca.0.9 ng/female. Field bioassays in Kagoshima, Japan, showed that the two aldehydes are essential for male attraction and the alcohols may have a synergistic effect on the aldehydes. A rubber septum containing 0.9 mg of the four components at the natural ratio was shown to be an effective lure for monitoring this pest in Japan. The above four components are quite different from the sex pheromone components reported previously for the same species of either Philippine or Indian origin; components were shown to be (Z)‐11‐hexadecenyl acetate and (Z)‐13‐octadecenyl acetate at a ratio of 98:2 in the Philippine blend and 1:10 in the Indian blend. Furthermore, in the field tests in Japan, neither the Philippine blend nor the Indian blend showed any attractive activity, while the Japanese blend attracted significant numbers of male moths. These results suggest that there are remarkable geographical variations in the sex pheromone composition of this species or there are several distinct species using different sex pheromone blends.
Influence of thrips prey species on the life‐history and behaviour of Orius albidipennis
Authors: Fritsche Maria Elena , Tamò Manuele
Published: October 2003

The effects of two diets, i.e., cowpea leaves plus Megalurothrips sjostedti larvae versus cowpea leaves alone, on nymphal development and mortality of Orius albidipennis were studied under controlled laboratory conditions in Benin, West Africa. Nymphal development was longer when O. albidipennis was fed with cowpea leaves only, compared to the diet complemented with M. sjostedti larvae (17.6 days versus 14.8, respectively). Nymphal mortality was very high (78.6%) if fed with cowpea leaves only, and still relatively high if the diet was complemented with thrips larvae (44.4%).

In a separate study on the longevity and fecundity of O. albidipennis adult females feeding on M. sjostedti larvae, an average of 6.8 eggs per day (maximum 16 eggs) and a mean total fecundity of 61.1 eggs were observed. The females lived on average 13.5 days.

Finally, observations on the predation by O. albidipennis adults on three different thrips species revealed that M. sjostedti larvae were killed at a lower rate than larvae of Ceratothripoides cameroni and Frankliniella schultzei. Higher predation rates were measured using unmated females and males than in mated females. However, the rate of first attack, measured as first larva attacked in dual‐choice assays, was higher for M. sjostedti when a F. schultzei larva was offered simultaneously, and not different when a C. cameroni or Sericothrips adolfifriderici larva was offered.

The results of this study are discussed with regard to the lack of efficacy of O. albidipennis as biological control agent for M. sjostedti.
Odour sensitivity of antennal olfactory cells underlying grooved pegs of Anopheles gambiae s.s. and An. quadriannulatus
Authors: van, den Broek Ingrid V.F. , den Otter C.J.
Published: October 2003

In female mosquitoes of the anthropophilic species Anopheles gambiae Giles s.s. and the zoophilic An. quadriannulatus Theobald single sensillum recordings from grooved pegs were made. In both species, the majority of these sensilla responded to ammonium hydroxide, butylamine and propanoic acid, whereas a smaller part responded to acetone. Lactic acid, butanone, 3‐methyl phenol and 1‐octen‐3‐ol evoked responses in a minority of grooved pegs only. In An. gambiae these four substances evoked either excitatory or inhibitory responses. In An. quadriannulatus excitatory and inhibitory responses were only found on stimulation with lactic acid; butanone, 3‐methyl phenol and 1‐octen‐3‐ol only evoked inhibition in the pegs of this species. More than half of the grooved pegs responded to water vapour with an increase in spike frequency. As opposed to this, in some pegs inhibitory responses were found upon stimulation with vapour of low humidity. This suggests that grooved pegs may play a role in humidity perception in Anopheles. Dose‐response relations were investigated for cells excited by ammonium hydroxide, butylamine and propanoic acid. Excitatory responses to these three substances were dose‐dependent. No significant differences were found between the dose‐response curves of the two species. It is concluded that in both species the host odours tested are not perceived by specialist cells. Combined information from generalist cells may provide a detailed ‘odour profile’ of the host.
Local and distant prey‐related cues influence when an acarine predator leaves a prey patch
Authors: Mayland Holly , Margolies David C. , Charlton Ralph E.
Published: October 2003

Over relatively long distances, the predatory mite Phytoseiulus persimilis is able to detect volatiles produced by bean plants that are infested by its prey, Tetranychus urticae, the twospotted spider mite. Our investigation examined the separate and combined effects of prey, their products, and prey‐induced plant volatiles on when P. persimilis left a potential prey host plant. In wind tunnels, we assessed the relative importance of and interaction among local and distant prey‐related cues. The examination of local cues included: (1) all local cues (prey eggs, webbing, and prey‐induced plant volatiles), (2) food (prey eggs) and webbing only, (3) plant volatiles only, and (4) no prey‐related cues. The examination of distant cues involved the presence or absence of prey‐induced plant volatiles from upwind plants. External volatile cues, produced by placing prey‐infested plants upwind in the wind tunnel, resulted in more predators leaving downwind plants, and leaving sooner, than when clean plants were upwind, regardless of the availability of prey or prey‐related cues on the local plant. However, local cues, especially the presence of food/webbing, had a greater effect than distant cues on timing of predator leaving. Predators remained in larger numbers and for longer times on prey‐infested plants. However, the presence of either locally‐produced plant volatiles or food/webbing alone still reduced the number of predators leaving a plant in the first hour compared to clean plants. After the first hour, the number of predators leaving was primarily driven by the presence of food/webbing. When no food/webbing was available, predators left plants rapidly; if food/webbing was available, some predatory mites remained on plants at least 24 hours. Even if no food/webbing was available, predators presented with local volatiles remained on plants for several hours longer than on clean plants without local volatiles. These small changes in leaving rates may lead to differences in local population dynamics, and possibly regional persistence, of the predator‐prey interaction in patchy environments.
Spruce stands provide natural food sources to adult hymenopteran parasitoids of bark beetles
Authors: Hougardy E. , Grégoire J.‐C.
Published: October 2003

Adults of synovigenic hymenopteran parasitoids of bark beetles need supplemental feeding to maximise their lifetime realised fecundity, and yet little is known about the natural sources that provide this food. Here we show that, in spite of the reduced diversity of flowering plants expected in even‐aged spruce plantations, several plant species are present that might provide nectar and pollen to the hymenopteran parasitoid complex of Ips typographus L. (Coleoptera: Scolytidae), throughout the growing season. Conifer aphids are also abundant in these stands and produce large amounts of honeydew, which might also be consumed by the parasitoids. Laboratory experiments demonstrate that longevity is significantly increased in Coeloides bostrychorum Giraud (Hymenoptera: Braconidae) when the wasps are exposed to flowers of various species commonly found in spruce stands.
Female‐derived sex pheromone mediates courtship behaviour in the parasitoid Lariophagus distinguendus
Authors: Ruther Joachim , Homann Marion , Steidle Johannes L.M.
Published: October 2003

Courtship behaviour of the polyphagous ectoparasitoid Lariophagus distinguendus Först. (Hymenoptera, Pteromalidae) was studied. The initial behavioural element of the courtship sequence is a characteristic wing fanning shown by the males at encounters with females. Wing fanning and arrestment of the males was elicited by paper discs treated with dichloromethane extracts from virgin females showing the existence of a female‐derived sex pheromone. The pheromone is only active at a distance between 0–5 mm suggesting low volatility of the active compound(s). Females mate only once, and the pheromone is still perceived by males at least 5 days after female mating. Males exposed to dissected female heads, thoraces and abdomens, showed wing fanning towards all segments. However, extracts from female abdomens were significantly more active than those from heads or thoraces suggesting the pheromone source to be located in the abdomen.
Fitness costs of resistance to Bacillus thuringiensis in the Indianmeal moth, Plodia interpunctella
Authors: Oppert Brenda , Hammel Richard , Throne James E. , Kramer Karl J.
Published: October 2003

Genetic changes in insects that result in insecticide resistance can also affect their fitness. Here, we report measurements of development time and survival of the Indianmeal moth, Plodia interpunctella (Hübner), to compare the relative fitness of Bacillus thuringiensis (Bt)‐susceptible and ‐resistant colonies. Measurements of larval development time and survival indicated that a fitness cost was associated with resistance to Bt in some Bt‐resistant colonies but not others. Comparisons of geographically different populations revealed inherent differences in development time and survival. In most cases, Bt‐resistant moths suffered no disadvantage when feeding on a Bt‐treated diet. In many cases, the development of Bt‐resistant moths on Bt‐treated diet was slower than the unselected moths on untreated diet, but it is unclear whether these differences would affect the successful mating of susceptible and resistant moths.
Butterfly nectaring flowers: butterfly morphology and flower form
Authors: Corbet Sarah A.
Published: October 2003

The profitability of butterfly foraging depends in part on the corolla depth and clustering of flowers, and the tongue length, body mass and wing loading of butterflies. Interactions among these attributes of flowers and butterflies were investigated, using data from a field study in Cornwall and from Porter et al. (1992). The maximum corolla depth from which a butterfly can feed depends on tongue length, which correlates with the more easily measured attributes of body mass and wing loading. Small, short‐tongued butterflies did not visit deep flowers. The quantity of nectar sugar per flower necessary for profitable foraging depends on foraging costs, which are expected to correlate with wing loading. Butterfly species with a high wing loading generally confined their visits to flowers that were clustered or very nectar‐rich. Butterfly species with a low wing loading included solitary and less nectar‐rich flowers in their diet. Body mass and wing loading affect a butterfly's load‐carrying capacity (limiting the distance between fuelling stops) and cooling rate (limiting the distance between stops for basking or endothermic warming), and will therefore influence the capacity for floral selectivity and for migration and dispersal. Body mass, wing loading and tongue length characterised families or subfamilies of butterflies. For example vanessine nymphalids, with their long tongues and high wing loading, visited the deep, massed flowers of Buddleja davidii, but lycaenids, with their short tongues and low wing loading, did not. These often visited members of the Asteraceae. Eupatorium cannabinum, with massed flowers offering abundant and accessible nectar, was visited by butterflies of all tongue lengths and both high and low wing loading. These findings may help to inform habitat management for butterfly nectaring flowers.
Pre‐ and post‐landing response of the parasitoid Encarsia formosa to whitefly hosts on Gerbera jamesonii
Authors: Sütterlin S. , van Lenteren J.C.
Published: October 2003

One of the factors that may complicate biological control of the greenhouse whitefly on Gerbera jamesonii by Encarsia formosa is the rosette shape of this ornamental, which differs from the vertical shape of most vegetable plants (cucumber, egg plant, tomato, etc.). Therefore, host‐habitat location and the behaviour prior to landing on uninfested and infested leaves was studied. Attraction of E. formosa from a short distance by infested leaves could not be detected: the parasitoid females landed at random on uninfested and infested leaves. After the first landing, a redistribution of the wasps occurred on the leaves. After 24 h three times as many wasps were found on the infested leaves than on uninfested ones. In a dispersal experiment with four plants, E. formosa appeared to have no preference for landing on leaves of the medium age class, which is the age class on which most of the whiteflies in a suitable stage for parasitism occur. Twenty percent of the parasitoids were found on the plants 20 min after releasing them. These results were independent of the plant cultivar and the host density on the plants. In the course of 8 h, the number of E. formosa females recovered from plants increased linearly, and this increase was greater on plants where hosts were present and also greater on the plant cultivar with the lowest trichome density. After 24 h, the percentage of females was highest (56%) on plants with the highest host density. E. formosa females were arrested on leaves where hosts were present. Contrary to our expectation, the results from the two G. jamesonii cultivars that differed strongly in leaf hairiness were not significantly different in most experiments. Only at the high host density was parasitism found to be lower on the cultivar with the higher hair density. Parasitoids may walk on top of the ‘hair coverlet’ of cultivars with high trichome density and, therefore, be hampered less than expected.
Diapause induction in aphid parasitoids
Authors: Polgár L.A. , Hardie Jim
Published: October 2003

Diapause is one of the adaptations that insects have evolved for the synchronisation of their life cycle with seasonal climatic changes and resources. In aphid parasitoids, univoltine species have an obligatory, genetically determined diapause. Polyvoltine species, on the other hand, use a variety of abiotic (temperature, photoperiod) and biotic (host insect or/and host plant) signals for the induction of diapause. We present an overview of the role of these environmental cues in diapause induction in specialist and generalist aphid parasitoids, and discuss possible endocrine factors that may be involved in diapause induction.
Individual behaviour and population dynamics: lessons from aphid parasitoids
Authors: Mondor Edward B. , Roitberg Bernard D.
Published: October 2003

An increasing number of researchers are studying behaviour in the hopes of understanding population dynamics or improving biological control efforts of insect pests by natural enemies. However, it is unclear exactly how behavioural studies will improve our understanding of these population level processes. In this paper we argue that in order to understand population level processes, the problem must be approached from a population biology perspective. A comprehensive understanding of certain behaviours will provide little towards our understanding of host‐natural enemy interactions. For example, using an aphid‐parasitoid model, we examined the effect that a commonly studied behaviour, variance in host selection by aphid parasitoids, has on aphid‐parasitoid population dynamics. Differential host selection does not qualitatively alter classic Nicholson‐Bailey dynamics, but only results in quantitative differences in aphid‐parasitoid population sizes. Irrespective of the degree of aphid instar preference, a large increase in the number of aphids is followed by a large increase in the number of parasitoids, decimating the aphid population. Thus, studying some behaviours, such as variance in host selection, will not contribute substantially to an understanding of aphid‐parasitoid population dynamics.
Understanding insect endocrine systems: molecular approaches*
Authors: Lafont René
Published: October 2003

Molecular approaches have led to spectacular improvement of our knowledge of insect endocrinology. The present review focuses on two major classes of insect lipidic hormones, ecdysteroids and juvenile hormones. Although the ecdysteroid biosynthetic pathway is not yet fully elucidated, several new steps have been recently characterized, and molecular studies of biosynthetic enzymes are now beginning. It is expected that, thanks to suitable biological models (e.g., ecdysteroid‐defective mutants of Drosophila), the entire biosynthetic pathway will be elucidated in the near future. The understanding of the ecdysteroid mode of action has benefited from studies with Drosophila and major developments relate to the cascades of gene activation and the molecular basis for the stage‐ and tissue‐specificity of hormonal effects. The biosynthetic pathway of juvenile hormones is fully known, but molecular studies of enzymes are still in their infancy, and there is some controversy about the nature of juvenile hormone receptors. Within the forthcoming years, molecular tools will allow to characterize all the enzymes involved in hormone biosynthesis and then to analyze the fine regulation of hormone titers. They will also allow comparative studies aimed at investigating the presence of related molecules (hormone biosynthetic enzymes and receptors) among other Invertebrates (Arthropods and non‐Arthropods), and thus to propose evolutionary scenarios for their endocrine systems.
Effects of host age on parasitism and progeny allocation in Trichogrammatidae
Authors: Godin Claude , Boivin Guy
Published: October 2003

The impact of host age on the number of hosts killed, survival of progeny, progeny allocation, and sex allocation was examined for several Trichogrammatidae (Hymenoptera) species in laboratory choice tests. Individual female parasitoids were provided with young, medium‐aged and old eggs of one of three lepidopterous host species: Trichoplusia ni (Hübner) (Noctuidae), Pieris rapae (L.) (Pieridae), or Plutella xylostella (L.) (Plutellidae). Trichogrammatid species behaved as gregarious parasitoids with the first two host species, and as solitary parasitoids with eggs of the smaller latter one. They mostly preferred young eggs of T. ni, but did not discriminate among P. rapae eggs of different ages, and often preferred young or medium‐aged P. xylostella eggs over old eggs. Survival of progeny did not vary constantly with host age, although it was often very low in P. rapae eggs of any age. Clutch size frequently decreased with host age in both T. ni and P. rapae. Offspring sex ratio did not change with age of T. ni and P. rapae eggs, and rarely did so in P. xylostella eggs. In regard to host age, the results with T. ni are the ones which are the most in agreement with optimal foraging theoretical predictions, as clutch size was the highest in preferred younger eggs.
Electrical Penetration Graph analysis reveals population differentiation of host‐plant probing behaviors within the aphid species Uroleucon ambrosiae
Authors: Bernays Elizabeth A. , Funk Daniel J.
Published: October 2003

Uroleucon ambrosiae collected from the eastern and the southwestern United States were studied in relation to host‐plant probing. In the field, eastern aphids are highly specific on Ambrosia trifida, while southwestern aphids feed on Ambrosia trifida plus many other species in the family Asteraceae. Electrical penetration graphs of insects on the principal host, A. trifida, and an additional host of southwestern populations, Heterotheca subaxillaris, revealed regional differentiation in host‐associated aphid behaviors, specifically in the first phase of subcuticular probing, and in phloem finding activities. Eastern aphids used A. trifida more efficiently than southwestern aphids, but were demonstrably less vigorous in their probing activities on H. subaxillaris.
Difficulties in location and acceptance of phloem sap combined with reduced concentration of phloem amino acids explain lowered performance of the aphid Rhopalosiphum padi on nitrogen deficient barley (Hordeum vulgare) seedlings
Authors: Ponder K.L. , Pritchard J. , Harrington R. , Bale J.S.
Published: October 2003

Effects of nitrogen deficiency in hydroponically grown barley seedlings (Hordeum vulgare L.) on the development and reproduction of the aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were investigated.

Plant growth was significantly reduced in seedlings grown without nitrogen. Aphid intrinsic rate of increase (rm) was also significantly lower on these plants compared with that on plants grown with 8 mol m−3 nitrogen. Phloem sap was collected from seedling stems by aphid stylectomy and amino acids quantified by HPLC. There was a significant reduction in the concentration of non‐essential amino acids as a group, but not of essential amino acids. Electrical penetration graphs (EPG) indicated that aphids reached the phloem more quickly and fed for longer on plants grown with nitrogen. This is the first reported study in which this combination of techniques has been used to understand the interactions of an aphid and plant under different environmental conditions.
Local enhancement of arrivals of Ceratitis capitata females on fruit mimics
Authors: Prokopy Ronald J. , Miller Neil W. , Duan Jian J. , Vargas Roger I.
Published: October 2003

Mature female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), isolated from conspecifics for 7 days prior to testing in laboratory cages, were attracted to yellow plastic fruit‐mimicking hemispheres or spheres in significantly greater numbers when groups of conspecific females were present than absent on fruit mimics. Attraction of females to conspecifics occurred for females deprived of protein or continuously provided with protein since eclosion, for fruit mimics that were unbaited or baited with odor of food or fruit, and under single‐choice as well as multiple‐choice test conditions. Attraction proved just as great to fruit mimics having dead conspecifics as to mimics having live conspecifics, was evident also when fruit mimics were orange or white, and occurred also in response to presence of live Bactrocera dorsalis (Hendel) females on fruit mimics. We discuss our findings in relation to local enhancement, a form of social facilitation in insects and other animals.
Parasitoid‐plant mutualism: parasitoid attack of herbivore increases plant reproduction
Authors: van Loon Joop J.A. , de Boer Jetske G. , Dicke Marcel
Published: October 2003

We tested whether a plant's life time seed production is increased by parasitization of herbivores in a tritrophic system, Arabidopsis thaliana (Brassicaceae) plants, Pieris rapae (Lepidoptera: Pieridae) caterpillars and the solitary endoparasitoid Cotesia rubecula (Hymenoptera: Braconidae). We established seed production for intact A. thaliana plants, plants that were mechanically damaged, plants fed upon by parasitized caterpillars and plants fed upon by unparasitized caterpillars. In the first experiment, with ecotype Landsberg (erecta mutant), herbivory by unparasitized P. rapae caterpillars resulted in a strongly reduced seed production compared to undamaged plants. In contrast, damage by P. rapae caterpillars that had been parasitized by C. rubecula did not result in a significant reduction in seed production. For the second experiment with the ecotype Columbia, the results were identical. Plants damaged by unparasitized caterpillars only produced seeds on regrown shoots. Seed production of plants that had been mechanically damaged was statistically similar to that of undamaged plants. Production of the first ripe siliques by plants fed upon by unparasitized caterpillars was delayed by 18–22 days for Landsberg and 9–10 days for Columbia. We conclude that parasitization of P. rapae by C. rubecula potentially confers a considerable fitness benefit for A. thaliana plants when compared to plants exposed to feeding damage by unparasitized P. rapae larvae. Plants that attract parasitoids and parasitoids that respond to herbivore‐induced plant volatiles will both experience selective advantage, justifying the use of the term mutualism for this parasitoid‐plant interaction. This type of mutualism is undoubtedly very common in nature.
Effect of parasitism on a nucleopolyhedrovirus amplified in Spodoptera frugiperda larvae parasitized by Campoletis sonorensis
Authors: Escribano Ana , Williams Trevor , Goulson David , Cave Ronald D. , Chapman Jason W. , Caballero Primitivo
Published: October 2003

We evaluated the consequences of parasitism by the solitary ichneumonid endoparasitoid Campoletis sonorensis (Cameron) towards the replication, genetic composition and virulence of a nucleopolyhedrovirus (Baculoviridae) originating from Spodoptera frugiperda (J. E. Smith) larvae. Parasitism by C. sonorensis and viral infection of third and fourth instar S. frugiperda larvae resulted in reduced growth compared with nonparasitized control larvae. A positive correlation was observed between virus yield and larval instar at the moment of infection. When larvae were virus‐inoculated in the fourth instar, parasitism resulted in a significant reduction in mean per capita virus yield compared to the virus yield from nonparasitized larvae. In an experiment involving 10 serial passages of virus in both parasitized and nonparasitized larvae, restriction endonuclease analysis of viral DNA amplified in nonparasitized larvae revealed the presence of the wild‐type virus as well as three additional variants (A, B, and C) diagnosed by the presence of novel submolar PstI fragments of different sizes. In contrast, analysis of viral DNA from parasitized larvae showed the presence of the wild‐type virus and two other variants (E and F), each characterized by a different submolar BglII fragment. Southern blot analysis indicated that the submolar fragments of variants E and F contained sequences originating from the viral genome. Bioassay of the different virus variants in S. frugiperda larvae indicated that their virulence was equal or less than that of the wild‐type virus. We conclude that parasitism can affect the quantity of virus produced in dually infected and parasitized larvae, but no adverse effects were detected in terms of the biological activity of the virus.
Phenotypic characteristics and relative proportions of three genotypic variants isolated from a nucleopolyhedrovirus of Spodoptera exigua
Authors: Muñoz Delia , de Escudero Iñigo Ruiz , Caballero Primitivo
Published: October 2003

US2A, US2D, and US2F are three in vivo cloned genotypic variants from the wild‐type strain of a Spodoptera exigua nucleopolyhedrovirus (SeMNPV) isolated in Florida (USA) and is the active component of the commercial bioinsecticide Spod‐X®. These variants were compared in terms of pathogenicity (LD50), speed of kill (expressed as mean time to death) and viral progeny productivity (OBs/larva). LD50 values were similar for the three cloned genotypes. The mean time to death value for US2D (113.7 h) was significantly higher than those of US2A (31.7 h) and US2F (27.8 h). Virus yield was determined for L4 larvae infected with the estimated LD99. US2D infected larvae attained higher weight than those infected with US2A and US2F, and produced a higher OB yield than larvae infected with US2A or US2F. An outstanding feature of US2F, in contrast to US2A and US2D, was its inability to disrupt the teguments of NPV‐killed larvae. To study the relative proportion of the three genotypic variants throughout successive passages, S. exigua larvae were originally infected with a viral inoculum containing a 1:1:1 mixture of the three genotypes. After three successive passages, US2D was no longer detected in either of the three replicate experiments performed, while US2A was the predominant genotype in all of them, and US2F remained at similar proportions throughout the three passages. The influence of the phenotypic characteristics of the three variants on their relative proportions in mixed infections is discussed.
Comparative trials on the effects of two fungicides on a predatory mite in the laboratory and in the field
Authors: Blümel S. , Pertl C. , Bakker F.M.
Published: October 2003

Both laboratory tests with the open glass plate method of Louis & Ufer (1995) and a field study in a vineyard were carried out to test the side effects of the two fungicides, Dithane Ultra WG75 and Polyram Combi WG70, on the predatory mite Typhlodromus pyri Scheuten (Acarina: Phytoseiidae). The effects of both fungicides in the residual contact test in the laboratory were more pronounced than the actual effects obtained in the field even after multiple application of the test products. The study results suggest, that for the selected test products the current laboratory guidelines correctly triggered the field test. Methodological problems of the laboratory test due to the repellent effect of the fungicides are discussed.
Host range and gene contents of Bacillus thuringiensis strains toxic towards Spodoptera exigua
Authors: Porcar Manuel , Martínez Clara , Caballero Primitivo
Published: October 2003

Thirty‐five strains of the entomopathogenic bacterium Bacillus thuringiensis active on Spodoptera exigua, were characterized by means of serological identification and determination of cry gene contents by PCR. The insecticidal activity of these 35 strains was further confirmed against S. exigua and tested against two other species of the same genus: S. littoralis and S. frugiperda. The results indicate that serovars aizawai, thuringiensis, and kurstaki were the most frequent within S. exigua ‐active strains and that serovar aizawai had the highest number of strains exhibiting toxicity against the three species bioassayed. The presence in cry genes as determined by PCR suggests a non random distribution of some cry genes among serovars. Genes cry1C, cry1D, and cry1E, which are known to code for proteins toxic against Spodoptera species, were very common within S. exigua‐active strains, specially in those belonging to serovar aizawai. However, some strains harbouring one or more of these genes were not toxic to S. littoralis or S. frugiperda; and some strains lacking all of the Spodoptera‐active genes were found to be toxic to all three species. This suggests differences in the expression levels among strains bearing toxic genes and the involvement of other genes toxic to Spodoptera species. Since strains sharing the same cry genes exhibited different host ranges, the results indicate the need to perform toxicity bioassays in addition to other tests (serological identification and PCR) in order to determine the insecticidal activity of B. thuringiensis strains.
Age‐dependent insemination success of sterile Mediterranean fruit flies
Authors: Taylor P.W. , Kaspi R. , Mossinson S. , Yuval B.
Published: October 2003

The Sterile Insect Technique (SIT) is used in many regions worldwide to manage wild populations of the Mediterranean fruit fly (‘medfly’), an important pest species. This technique relies on released sterile males outcompeting their wild counterparts in fertilizing ova of wild females. Numerous studies have investigated the ability of sterile males to secure copulations, an essential step toward overall success. Here we progress further along the mating sequence by studying reproductive barriers that may remain ahead of sterile males that manage to secure copulations in field cage experiments and whether ability to pass these barriers is influenced by a male's age, diet and size, or the size of his mate. Amongst those virgin males that succeeded in copulating, both the number of sperm stored by mates and the chances of having any sperm stored at all decreased with age. Sperm tended to be stored asymmetrically between the females' two spermathecae, and this tendency was more apparent when few sperm were stored. In accord with effects of male age on number of sperm stored, sperm of older males were stored more asymmetrically than that of young males. We found no evidence that male size, male diet or female size influenced copula duration, number of sperm stored or allocation of sperm between the female's two spermathecae. The decline in number of sperm stored as males aged was not accompanied by age‐dependent changes in copula duration, indicating that copula duration and insemination success are not deterministically linked. We discuss these results in light of their relevance to SIT and the medfly mating system.
Early oviposition experience affects patch residence time in a foraging parasitoid
Authors: Keasar Tamar , Ney‐Nifle Muriel , Mangel Marc , Swezey Sean
Published: October 2003

Parasitoids learn olfactory and visual cues that are associated with their hosts, and use these cues to forage more efficiently. Classical conditioning theory predicts that encounters with high‐quality hosts will lead to better learning of host‐associated cues than encounters with low‐quality hosts. We tested this prediction in a two‐phase laboratory experiment with the parasitoid Trichogramma thalense Pinto & Oatman (Hymenoptera: Trichogrammatidae) and the host Anagasta kuehniella Zeller (Lepidoptera: Pyralidae).

Host quality during the first exposure to hosts affected later foraging behavior for some experimental treatments, as predicted. We used a learning model, followed by patch‐time optimization, to interpret our findings. We first simulated the parasitoids' host encounters during the experiment, and predicted their estimate of patch quality after each encounter. We then used dynamic optimization to predict the parasitoids' optimal patch residence times. The model reproduces the trends of the experimental results.
The effects of wilt symptom development and peroxidase induction on interactions between vascular wilt bacteria and cucumber beetles
Authors: Moran Patrick J.
Published: October 2003

Infection of cucumber (Cucumis sativus L.) with the bacterial pathogen Erwinia tracheiphila E. F. Smith causes vascular wilt disease in leaves, which may alter the suitability of the host plant for insects and other pathogens. In this study, densities of spotted (Diabrotica undecimpunctata howardi Barber) and striped (Acalymma vittata (Fab.) cucumber beetles (Coleoptera: Chrysomelidae) were higher on wilted leaves of mature and seedling field plants inoculated with E. tracheiphila. Bacterial infection or feeding by D. undecimpunctata howardii beetles increased total peroxidase enzyme activity in inoculated or infested leaves of greenhouse seedlings, but only beetle feeding induced higher activities in untreated systemic leaves on the same plants. Neither bacterial infection nor beetle infestation led to the development of systemic acquired resistance (SAR) to the fungal pathogen Colletotrichum orbiculare (Berk & Mont.) Arx. Susceptibility to this fungus was greater on E. tracheiphila‐infected plants than on controls. The positive association between leaf wilt symptom development and beetle occurrence thus occurs in the presence of an oxidative but not anti‐pathogenic response induced by both the insect and the pathogen.
15N‐enrichment of plant tissue to mark phytophagous insects, associated parasitoids, and flower‐visiting entomophaga
Authors: Steffan Shawn A. , Daane Kent M. , Mahr Daniel L.
Published: October 2003

New techniques are presented on the use of 15N to mark insects. 15N, a stable isotope of nitrogen, was enriched above natural abundance in plant and insect tissues. Two laboratory studies demonstrated that enriched 15N‐concentrations could be tracked from plant to insect using mass spectrometry. In the first study, adult Cotesia plutellae (Kurdjimov) (Hymenoptera: Braconidae) and Hippodamia convergens Guérin‐Méneville (Coleoptera: Coccinellidae) were allowed to feed at the flowers of rapid‐cycling Chinese cabbage plants that had been fertilized with 15N‐enriched potassium nitrate (KNO3‐15NO3). Both insect groups were found to have significantly elevated 15N levels after visiting the flowers of the 15N‐enriched plants for 48 hours. In the second study, 15N‐enriched bean plant (Phaseolus vulgaris L.) tissue was incorporated into an insect diet and fed to navel orangeworms, Amyelois transitella (Walker) (Lepidoptera: Pyralidae). When the navel orangeworm larvae were 4th instars, they were removed from the diet and exposed to the parasitoid, Goniozus legneri Gordh (Hymenoptera: Bethylidae). Results indicated that the enriched 15N‐concentration of the bean plants was transferred to the navel orangeworms and, subsequently, to the parasitoids. This work may provide useful techniques to help establish whether agriculturally important entomophaga visiting 15N‐enriched flowers or parasitizing enriched sentinel larvae in the field can be effectively marked with 15N.
Electronically monitored cowpea aphid feeding behavior on resistant and susceptible lupins
Authors: Zehnder Geoffrey W. , Nichols Amy J. , Edwards Owain R. , Ridsdill‐Smith T. James
Published: October 2003

The feeding behavior of cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) was examined on seedlings of narrow leafed lupin, Lupinus angustifolius L., and yellow lupin, L. luteus L., using electronic monitoring of insect feeding behavior (EMIF). Aphid feeding behavior was first compared between resistant (cv. Kalya) and susceptible (cv. Tallerack) varieties of narrow‐leafed lupin. Aphids spent significantly more time in non‐ penetration and stylet pathway activities, and significantly less time in the sieve element phase on Kalya than on Tallerack, suggesting that feeding deterrence is an important component of aphid resistance in Kalya. Aphid feeding on a susceptible yellow lupin variety (cv. Wodjil) was then compared with that on two resistant lines, one (Teo) with high and the other (94D024‐1) with low seed alkaloid content. There were no consistent differences in aphid feeding behavior between Wodjil and Teo. Total, mean and percentage sieve element phase times were significantly lower, and total and percentage times in non‐phloem phase were greater on 94D024‐1 than on Wodjil, suggesting the possibility of phloem‐based deterrence in 94D024‐1.