bluuebunny/crossref_metadata_2025 huggingface dataset:
Trap color and placement affects estimates of insect family‐level abundance and diversity in a Nebraska salt marsh
Authors: Hoback W. Wyatt , Svatos Tina M. , Spomer Stephen M. , Higley Leon G.
Published: October 2003

Sampling programs to establish baseline ecosystem information (e.g., species abundance and diversity) often fail to consider the potential influence of sampling techniques on results. Research on sampling economically important insects has demonstrated the possible influences of trap color and trap placement on results, but few data have been collected from natural environments. Consequently, we examined the effects of color (yellow and blue) and placement (exposed and shaded by plants) of sticky traps on insect captures and diversity estimates from a Nebraska inland salt marsh community. We identified 1913 specimens from 67 insect families collected during five trapping dates in July 1996. More Cicindelidae were collected on exposed traps, and more Staphylinidae, Dolichopodidae, Cicadellidae, and Thripidae were collected on shaded traps. More Dolichopodidae were collected on yellow traps, while more Syrphidae and Thripidae were collected on blue. Shannon and alpha diversity measures were significantly higher for shaded traps than exposed traps, but were not affected by trap color. Our results highlight the importance of characterizing sampling techniques when establishing diversity estimates. These data provide the first complete accounting of community‐level insect response to colored sticky traps and provide new information for color preference of non‐economic insect species.
Predicting spring emergence of blackcurrant leaf midge (Dasineura tetensi) from air temperatures
Authors: Cross J.V. , Crook D.J.
Published: October 2003

The mean duration of post‐diapause development of overwintered Dasineura tetensi larvae (in cocoons) was 72.8 (SD=11.4), 45.9 (SD=8.6), 28.7 (SD=6.0), 15.9 (SD=4.3), 10.4 (SD=1.9) and 10.2 (SD=1.8) days at constant temperatures of respectively 10, 12.5, 15, 17.5, 20 and 25 °C in the laboratory. No perceptible development occurred at 5 or 7.5 °C and complete mortality occurred when larvae were held at 30 °C for prolonged periods. The relationship between development rate (r days−1) and temperature (T °C) was sigmoidal between 10 and 25 °C, the logistic equation r=0.0158+0.085/(1+exp(−0.696(T−17.0))) accounting for 98% of the variation. Larvae entered the winter in diapause. Populations of cocoons were greatest in the surface soil in the centre of bushes adjacent to the crown, 69, 15, 9 and 6% of cocoons occurring in the top 0–1, 1–2, 2–3 and 3–4 cm of the soil, respectively. The time of termination of diapause in the field varied greatly between individuals and from season to season but a significant proportion (>40%) had broken diapause by the end of January in each of the three seasons studied. Diapause was not terminated in the laboratory by chilling over‐wintered larvae in cocoons at −2.5, 2.5 or 10 °C for up to 28 days nor when held in a L16:D8 photoperiod. A computer‐based phenological forecasting model was constructed using the development rate values (using the INSIM software developed at The Agricultural University, Wageningen, The Netherlands). The model accumulated daily development amounts calculated from daily maximum and minimum air temperatures from 1 February, the end of the coldest period of the year on average and before significant post‐diapause development occurred. The model uses boxcar trains to simulate dispersion. The model predicted the time of first emergence of D. tetensi adults in spring at HRI‐East Malling generally to within 6 days of the observed time of emergence, and to within 11 days at worst. There was poorer agreement between observed and predicted times of emergence when daily maximum and minimum soil temperatures (depth ca. 3 cm) were used. The use of the model to time insecticidal sprays in relation to the flowering time of blackcurrant is discussed.
Response of an aphid parasitoid, Aphelinus asychis to its host, plant, host‐plant complex, and to malathion
Authors: Rao A. , Vinson S.B. , Gilstrap F.E. , Michels G.J.
Published: October 2003

Aphelinus asychis (Walker) can be valuable as a biocontrol agent of the aphid, Schizaphis graminum (Rondani), a major pest on grain crops in the United States. This study reports the wind tunnel, and olfactometric responses of this parasitoid to the host (aphid), plant (sorghum), and host‐plant complex (aphid‐infested sorghum). In addition, the parasitoids' response to malathion‐treated plants is also presented. The goal of the present study was to test the hypothesis that volatiles associated with the host attract natural enemies, as reported in cases of many hymenopterous parasitoids, and also to learn about the effects of insecticides on these parasitoids. In wind tunnel studies, these parasitoids moved upwind in the direction of the host‐infested plant. There was no direct flight observed, however, these parasitoids were observed to hop and jump, and sometimes walk to their host. In the olfactometer experiments, we found that A. asychis is attracted to host‐plant complex. The parasitoids' response to malathion in the olfactometer suggested that a malathion formulation when applied to plants can lure these beneficials, thus providing new insight into the ongoing task of integrating chemical and biological control of insect pests.
Movement of Anastrepha fraterculus from native breeding sites into apple orchards in Southern Brazil
Authors: Kovaleski Adalecio , Sugayama Regina L. , Malavasi Aldo
Published: October 2003

We report movements exhibited by adults of Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) from patches of native forests into apple orchards in Southern Brazil. Two mark‐release‐recapture experiments were conducted using wild flies. Released flies behaved as wild unmarked flies, and periods of peak captures of marked adults coincided with those of unmarked ones. In the first experiment (December 94), out of 2154 released adults, 7.1% were recaptured from day 2 through day 20 after release. Captures peaked from day 7–9 after release. Most marked flies (94.7%) were trapped within 200 m of the release point but eight adults (seven females and one male) were captured in traps placed in an apple orchard, 400–800 m from the release point. The vegetation found between forest and orchard consisted of pastures and annual crops. In the second experiment (January 95), a total of 3284 flies was released in an area where native host plants were abundant and located at ca. 900 m from an apple orchard. In all, 37.1% of marked flies were captured, 99.0% of them at a distance of less than 200 m from the release point. Four adults were captured in an apple orchard, 7 to 24 days after release. They may have reached the orchard through a large and continuous area of native forest. Our results unequivocally demonstrate that A. fraterculus adults are able to disperse from native forests where they originate and invade apple orchards, probably foraging for food and oviposition sites.
Influence of host density on the reproductive strategy of Cephalonomia stephanoderis, a parasitoid of the coffee berry borer
Authors: Lauzière Isabelle , Pérez‐Lachaud Gabriela , Brodeur Jacques
Published: October 2003

The effect of the density of the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae) on reproductive and host‐feeding behaviours of the parasitoid Cephalonomia stephanoderis (Hymenoptera: Bethylidae) was evaluated under laboratory conditions. The number of hosts used for oviposition was density‐dependent at low host density. Beyond a density of six hosts/day, the oviposition rate reached a maximum of 1.2 eggs/day due to egg limitation. Cephalonomia stephanoderis females responded to increasing host availability with a linear increase in host feeding. Overall, parasitoids killed more coffee berry borers by feeding and paralysis than by parasitism. At low host density, the pre‐oviposition phase was extended, oogenesis was delayed, more males were produced, and host feeding occasionally occurred concurrently with oviposition. We suggest that the efficacy of C. stephanoderis as a biological control agent depends on seasonal variations in host density. Inoculative vs inundative releases in coffee plantations are discussed in relation to the abundance of the coffee berry borer during the fructification and interharvest periods.
Effects on oviposition behaviour and larval development of Spodoptera littoralis by herbivore‐induced changes in cotton plants
Authors: Anderson P. , Alborn H.
Published: October 2003

Herbivore feeding induces chemical defence responses in plants. In this study we investigate how herbivore‐induced changes in cotton plants, Gossypium hirsutum L., influence the oviposition behaviour and larval development of Spodoptera littoralis Boisd. (Lepidoptera: Noctuidae). In two‐choice experiments female moths preferred to oviposit on small plants (3–4 leaves) that had been fed on by 3rd to 4th instar larvae (72%) over non‐damaged control plants. However, when using larger plants (8 to 10 true leaves) the preference was reversed, with only 31% of the eggs deposited on the induced plants. The same trend was found with plants that had been given a similar level of damage by 6th instar larvae. However, the difference between the treatments was in both cases smaller with only 60% of the eggs deposited on the preferred plant treatment. If cotton plants subjected to artificial damage were compared with undamaged plants, none of the treatments were preferred for oviposition. No significant difference was found in larval weight, pupal weight, survival, or development time, between larvae reared their entire development on leaves from induced or from non‐induced plants.
Reproductive abnormalities in tsetse flies in Zimbabwe
Authors: Hargrove J.W.
Published: October 2003

Between November 1988 and July 1995 five technicians carried out ovarian dissections on 16,013 Glossina morsitans morsitans Westwood and 123,848 G. pallidipes Austen captured at Rekomitjie Research Station, Zambezi Valley, Zimbabwe. The ovarian age and uterine content were recorded, as were the lengths (l1, l2 and lu) of the largest and second largest oocyte, and of any uterine inclusion. Major abnormalities and abnormal spermathecal contents were found in <0.1% of all flies dissected. Apparent abortions rates varied significantly between dissectors and occurred at frequencies of 0.8–4.5% in G. m. morsitans and 0.3–2.8% in G. pallidipes. The lowest estimates give the best picture of the field situation. Abortion rates were higher in flies caught on electric nets than in trapped flies where the rate was only 0.15%, indicating that reproductive losses are negligible for most of the year at Rekomitjie. The rates did, however, increase to >2% when mean temperatures exceeded 27 °C and flies were captured in artificial refuges. There was little effect of ovarian age on the abortion rate, but the frequency of empty uteri declined markedly with age – with a suggestion, however, that it might increase again in the oldest flies. A knowledge of the rates of reproductive loss is important for the construction of realistic models of the dynamics of tsetse populations.
The relationship between cabbage root fly (Delia radicum) larval feeding and the freeze‐dried matter and sugar content of Brassica roots
Authors: Hopkins R.J. , Griffiths D.W. , McKinlay R.G. , Birch A.N.E.
Published: October 2003

Five genotypes of swede (Brassica napus var. napobrassica), two genotypes of kale (B. oleracea var. acephala), and two genotypes of rape (B. napus var. napus) were each inoculated at the 8–10 true leaf stage with five cabbage root fly (Delia radicum) eggs. The percentage pupation after larval feeding on individual plant genotypes ranged from 45 to 78%, and the mean pupal weight from 6.5 to 13.0 mg. After 5 weeks, larval feeding damage had reduced root weight by up to 47%, compared with uninoculated plants. The dry matter content of undamaged roots was higher in the kales and rapes than in the swedes. Whilst the dry matter content of the rapes and swedes were not changed by D. radicum damage, that of the kales was elevated. The ethanol‐soluble sugar content of the root was reduced in all cases by D. radicum larval damage. However, the effect of D. radicum damage on the concentrations of individual sugars (glucose, fructose and sucrose) was crop‐ and genotype‐dependent. In the roots of kales and rapes, the glucose and fructose concentrations were either very low or unaffected by D. radicum damage, whilst both glucose and fructose were generally reduced in swede roots by D. radicum damage. The root sucrose concentration was either reduced or not significantly affected by D. radicum damage in all of the crop types tested. The percentage pupation and the mean pupal weight of D. radicum were inversely correlated to root freeze‐dried matter content. D. radicum pupal weight was positively correlated with root fructose, glucose and ethanol‐soluble sugar contents.
Temperature and plant nutrient effects on the development, survival and reproduction of Cinara sp. nov., an invasive pest of cypress trees in Africa
Authors: Kairo Moses T.K. , Murphy Sean T.
Published: October 2003

Cinara sp. nov., previously identified as Cinara cupressi (Buckton) (Homoptera: Aphididae), is an important alien aphid pest of cypresses and junipers, and invaded Africa in the late 1980s. The work reported here was carried out as part of a larger programme aimed at the classical biological control of the aphid in Africa. Basic life history attributes including life table statistics of the aphid were quantified in order to facilitate the development of efficient aphid culturing methods and essential baseline information necessary for the culturing of potential parasitoid biological agents prior to selection for introduction to Africa. Developmental rates and fecundity were studied under four constant temperatures (10 °C, 15 °C, 20 °C, and 25 °C). The effects of several plant nutrients (nitrogen, potassium and phosphorus) supplied at different dose levels on life history attributes of Cinara sp. nov. were also studied.

Unlike most other aphids, the apterous morph of Cinara sp. nov. developed through only three instars, and the alate four instars. The aphid is highly aggregative and exploits a wide range of feeding sites from young green branches to woody stems. The developmental period of Cinara sp. nov. ranged from 9.3 days at 25 °C to 22.3 days at 10 °C and the developmental threshold was 0.61 °C. Reproduction was delayed, because of the longer duration of development, and nymph production decreased with decreasing temperature. The intrinsic rate of increase ranged between 0.117 at 25 °C and 0.060 at 10 °C. Aphid size increased significantly as temperature was lowered. Wing formation was not induced when apterae were reared for up to three generations at each constant temperature but continuous crowding in the supply cultures held at 21 °C resulted in a high number of alates being formed. No appreciable effects of the different plant nutrients, supplied either singly or in combination, on the duration of instars or overall survival could be detected.
Responses to aphid sex pheromones by the pea aphid parasitoids Aphidius ervi and Aphidius eadyi
Authors: Glinwood R.T. , Du Y.‐J. , Powell W.
Published: October 2003

Aphidius ervi and Aphidius eadyi, two parasitoids of the pea aphid Acyrthosiphon pisum, were attracted to components of the aphid sex pheromone in laboratory bioassays. Pre‐test experience with host aphids in the presence of aphid sex pheromone did not affect the response of A. ervi to pheromone in a 4‐way olfactometer, compared with that of naive parasitoids. Aphidius ervi females exposed only to the pheromone prior to testing did not respond in the olfactometer, suggesting habituation to the foraging cue by the parasitoid. In a wind tunnel, aphid sex pheromone increased the attraction of A. ervi to the plant‐host complex (Vicia faba/A. pisum), suggesting an additive effect when two different foraging cues are present simultaneously.
Sources of variability in copula duration of Mediterranean Fruit Flies
Authors: Field Scott A. , Taylor Phillip W. , Yuval Boaz
Published: October 2003

Previous studies have reported considerable variation in copula duration in the Mediterranean Fruit Fly (medfly), Ceratitis capitata Weidemann (Diptera: Tephritidae). Presently, however, this variation is largely unexplained. In this study we measure copula duration in two medfly strains used in applied research in Israel and examine how much of the variation in copula duration is due to the strain, age, the time of day the mating begins and the relative size of the mating pair. We found the following: flies of a strain reared in the laboratory since 1976 (Vienna) copulated for longer than flies of a strain collected in 1969 and periodically refreshed with wild males (Sade); older flies copulated for longer than young flies; and pairs in which males were smaller than females copulated for longer than pairs in which males were larger or the sexes were more evenly size‐matched. The time of day the mating commenced (morning vs afternoon) had no effect. We discuss potential mechanisms underlying these variations in medfly copula duration.
The effect of aphid prey quality on searching behaviour of Adalia bipunctata and its susceptibility to insecticides
Authors: Kalushkov P.
Published: October 2003

After consumption of one individual of a suitable prey, such as Phorodon humuli (Schrank) (Aphididae), Adalia bipunctata L. (Coleoptera, Coccinellidae) adults changed from extensive to intensive searching behaviour. However, after the consumption of one individual of three other aphid species: Aphis fabae Scop., Aphis craccivora Koch or Aphis spiraephaga Müller, which are unsuitable prey, this coccinellid remained immobile for 12–76 min and did not switch to intensive search after moving off. Adult A. bipunctata fed an unsuitable prey, A. fabae, for 2 weeks were 2–4 times more susceptible to pyrethroid insecticides (permethrin, deltamethrin, fenpropathrin, esfenvalerate, alfa‐cypermethrin and bioresmethrin) and insect growth regulators (diflubenzuron, triflumuron, fenoxycarb, flufenoxuron, teflubenzuron) than those fed a suitable prey, P. humuli.

The searching behaviour of coccinellids could thus be another criterion for determining the suitability of aphids as prey. The fact that the nutritional quality of aphids can affect the susceptibility of predatory coccinellids to insecticides should be borne in mind in integrated pest management programs.
Influence of species of host plants on the predation of thrips by Neoseiulus cucumeris, Iphiseius degenerans and Orius laevigatus
Authors: Brown A.S. Scott , Simmonds M.S.J. , Blaney W.M.
Published: October 2003

A leaf‐disc bioassay was used to compare the predation levels of two species of predatory mites (Neoseiulus cucumeris (Oudemans) and Iphiseius degenerans (Berlese)) and a predatory bug (Orius laevigatus (Fieber)), on the thrips Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouché), feeding on a range of susceptible plant species from twelve plant families. The predatory bug, O. laevigatus, reduced the number of thrips to a greater extent than the predatory mites and all three predators showed greater levels of predation on F. occidentalis than on H. haemorrhoidalis. The level of predation caused by each predator varied among the species of plants; the variation was greater on the plant hosts of H. haemorrhoidalis than of F. occidentalis.
Colour and odour responses of flying western flower thrips: wind tunnel and greenhouse experiments
Authors: Teulon David A.J. , Hollister Benedict , Butler Ruth C. , Cameron E. Alan
Published: October 2003

The behavioural responses of flying western flower thrips (Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae) to the colour yellow and the odour anisaldehyde were examined. In a wind tunnel, upwind flight by female thrips was common in an airflow of 0.11 m s−1 but was impeded at 0.22 m s−1. In the absence of anisaldehyde, flying female thrips exhibited an oriented response towards a yellow cue in the wind tunnel at a wind speed of 0.11 m s−1. The main response of females to anisaldehyde in the wind tunnel was flight inhibition. There was no evidence of an odour‐induced visual response, an odour‐induced anemotactic response or chemotaxis by female thrips to anisaldehyde in wind tunnel bioassays, but chemokinesis was implicated. With a matrix of yellow or black water traps with and without anisaldehyde in a greenhouse sweet pepper crop, yellow traps with anisaldehyde caught more thrips adults than yellow traps without anisaldehyde, black traps with anisaldehyde and black traps without anisaldehyde (1.3, 28 and 721 times for males respectively and 2.4, 9 and 117 times for females, respectively). Differences between respective traps were statistically significant in almost all cases. Trapping experiments using a centre‐baited trap design to reduce the interaction of anisaldehyde between baited and unbaited traps were undertaken in tomato and sweet pepper greenhouse crops. When the spatial distribution of the thrips adult population within the greenhouse was taken into account, yellow water traps with anisaldehyde caught between 11 and 15 times more female and 3 and 20 times more male F. occidentalis adults than yellow traps without anisaldehyde.
Changes in amino acids in Cucumis melo in relation to life‐history traits and flight propensity of Bemisia tabaci
Authors: Blackmer J.L. , Byrne D.N.
Published: October 2003

Phloem amino acids in Cucumis melo L. were measured to determine whether changes in nitrogen availability might affect life‐history traits and flight activity of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae). During plant development, nineteen of the twenty common amino acids, plus hydroxyproline, citrulline, ornithine and γ‐aminobutyric acid (GABA) were identified. For most essential amino acids, there were two peaks observed: an initial large peak associated with young plants, and a later small peak associated with senescing plants. For histidine, ornithine and citrulline, medium to large peaks in relative abundance were observed in mature plants. Arginine peaked during the first few weeks of development and was no longer detectable after wk 7. Serine and glutamine/glutamic acid were the only amino acids that peaked during plant senescence. Factor analysis was used to create a reduced number of orthogonal factors, which corresponded well with the trends that were observed for the various groups of amino acids. No single or combination of factors explained a significant amount of the variability in oviposition. For both males and females, factor 1 (predominantly essential amino acids) was the single most important predictor of adult weight. As the relative concentrations of essential amino acids decreased, whitefly weights decreased. Factors 1 and 3 (predominantly histidine and ornithine) were the most important predictors of developmental time. As these amino acids decreased in relative concentration, developmental time increased. Percent emergence was positively associated with factor 1 and negatively associated with factor 6 (predominantly aspartic acid). The distributions of flight duration for whiteflies emerging from young, mature and senescing melon plants were compared and they were always skewed towards short flights; however, the frequency of long‐duration flights increased when melon plants began to senesce. Whiteflies from all plant‐age categories were capable of flying for more than 2 h with fully developed eggs, but the presence of more than four mature eggs was associated with flights of reduced duration.
What is the basis of pederin polymorphism in Paederus riparius rove beetles? The endosymbiotic hypothesis
Authors: Kellner Rupert L.L.
Published: October 2003

Paederus riparius (Coleoptera:Staphylinidae) females are polymorphic with regard to their ability to synthesize the hemolymph toxin pederin, a character confined to that sex: (+)‐females endow their eggs with pederin whereas (−)‐females lay eggs devoid of the substance. When reared without access to conspecifics, (+)‐females can only be obtained from (+)‐mothers. Ingestion of (+)‐eggs during larval development, however, enables the offspring of (−)‐females to also become (+)‐females. This is only the case if untreated (+)‐eggs are eaten, while sterilized (+)‐eggs do not alter larval fate as (−)‐females. The character can thus be transferred to unrelated specimens. These experiments suggest that microorganisms might be involved in the biosynthesis of this unusual compound. Pederin appears to be the first defensive substance in insects traceable to endosymbionts.
The epizootiology of a Metarhizium infection in mini‐nests of the leaf‐cutting ant Atta sexdens rubropilosa
Authors: Jaccoud D.B. , Hughes W.O.H. , Jackson C.W.
Published: October 2003

There is growing interest in the use of entomopathogenic organisms to control leaf‐cutting ants (Hymenoptera: Formicidae: Attini). However, the way leaf‐cutting ants react as a colony to biohazards is poorly understood. We investigated the effects of Metarhizium anisopliae (Metschnikoff) (Deuteromycotina: Hyphomycetes) applied to the foraging arenas of mini‐nests (queenless sub‐colonies) of the leaf‐cutting ant Atta sexdens rubropilosa (Forel). Dry spores were applied either alone or mixed with citrus powder, at 0.5 g or 0.05 g per mini‐nest. The spores were removed four days after application, and all dead ants removed every three days. Ant numbers near the Metarhizium increased as the ants attempted to clean up the biohazard. The ants attempted to place the spores in piles, which they then covered over with other material. They were able to deal with the low doses in this way, but the high doses overwhelmed them. All treated mini‐nests suffered increased ant mortality during the first ten days after application. This mortality was particularly high in the media worker caste which had played the major role in attempting to clean up the spores. Foraging activity decreased, as did the health of the fungus gardens. The mini‐nests exposed to the low dose of spores mixed with citrus powder then recovered fully. The health of the other treated mini‐nests declined gradually until around 26 days after application, when they began deteriorating sharply. However, the decline of these mini‐nests after day 26 was not due directly to the pathogenic action of the Metarhizium, nor to the initial ant mortality it had caused. The results suggest that the social stress caused by even such a short‐lived Metarhizium epizootic was sufficient to cause the decline and ultimate death of the mini‐nests. This has important implications for the control of leaf‐cutting ants. It also demonstrates how important the social homeostasis of the colony is to leaf‐cutting ants.
Moisture is required for the termination of egg diapause in the chrysomelid beetle, Homichloda barkeri
Authors: Nahrung H.F. , Merritt D.J.
Published: October 2003

Four factors (moisture, light regime, temperature, food type) were examined for their effects on the embryonic diapause of Homichloda (Weiseana) barkeri (Jacoby) (Coleoptera: Chrysomelidae), a biocontrol agent for prickly acacia, Acacia nilotica (L.) Willdenew ex Delile (Mimosaceae). Moisture is critical for termination of diapause. A single wetting of eggs resulted in a low hatch rate while a sequence of wetting events followed by periods of dryness produced a high hatch rate. A relatively constant proportion of embryos within each batch initiated development at each wetting event, with hatching complete after the eighth wetting event in these trials. An extended interval between wetting events, tested at up to 23 days, did not result in a decreased overall hatch rate. A threshold time of exposure to moisture of between 3 to 6 h is required before development proceeds. The response of eggs to the moisture regime is seen as a strategy for taking advantage of available food after rainfall by terminating diapause, rather than merely a quiescent response to the absence of moisture. Temperature affected development time and the proportion of eggs that developed. Experimental manipulations of photoperiod and host‐plant availability showed no effect on embryonic development.
Role of host fruit color in the behavior of the walnut fly Rhagoletis juglandis
Authors: Henneman M. Lawrence , Papaj Daniel R.
Published: October 2003

Observations and sticky‐trap tests were used to assess the effect of fruit color on the behavior of adult male and female Rhagoletis juglandis Cresson (Diptera: Tephritidae), a tephritid that infests husks of Arizona walnut in southeastern Arizona. In the first experiment, during which flies were observed foraging among walnut models suspended from small walnut trees, models were painted green to appear ripe and uninfested or yellow with brown patches to appear ripe and infested. Flies used for this first experiment were also of two types: prior to observations, one group of flies had access to real walnuts for 1.5 days (prior experience) while the other group of flies was held without real walnut fruits (no prior experience). Regardless of prior experience with real walnut fruits, female flies landed on green models more than yellow/brown models. Experienced males also were more likely to land on green models than on yellow/brown models. More interactions also occurred on green models, because there were more landings.

In the field behavioral assay, flies from a natural population given a choice of green, yellow, and yellow/brown models landed most often on green models, and all interactions and oviposition attempts occurred on green models. Flies also distinguished models by color in field sticky trap assays.

These results suggest that female response to ripeness cues is innate, while males develop a preference for green based on their encounter rate with females.
The role of Pimpla hypochondriaca venom in the suppression of pupal Noctuid host immunity
Authors: Marris Gay C. , Bell Howard A. , Naylor Janet M. , Edwards John P.
Published: October 2003

When pupae of the Tomato moth (Lacanobia oleracea L.) (Lepidoptera: Noctuidae) are injected with venom from the endoparasitoid wasp Pimpla hypochondriaca Retzius (Hymenoptera: Ichneumonidae), they show an increased susceptibility to the fungal entomopathogen Metarhizium anisopliae Sorokin (Fungi Imperfecti: Deuteromycotina). This observation, coupled with the fact that wasp eggs are comparatively unlikely to be encapsulated when implanted into envenomated pupae, suggests that venom of P. hypochondriaca suppresses the cellular immune defense mechanisms of L. oleracea. Injection of host pupae with the venom of P. hypochondriaca has a rapid, adverse effect on the normal respiration pattern of L. oleracea. It is possible that severe disruption to host‐metabolism may contribute to a general failure in the hosts' normal immune response repertoire.
Attraction of a generalist predator towards herbivore‐infested plants
Authors: Venzon Madelaine , Janssen Arne , Sabelis Maurice W.
Published: October 2003

The occurrence and strength of interactions among natural enemies and herbivores depend on their foraging decisions, and several of these decisions are based on odours. To investigate interactions among arthropods in a greenhouse cropping system, we studied the behavioural response of the predatory bug Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) towards cucumber plants infested either with thrips (Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)) or with spider mites (Tetranychus urticae Koch (Acari: Tetranychidae)). In greenhouse release‐recapture experiments, the predatory bug showed a significant preference for both thrips‐infested plants and spider mite‐infested plants over clean plants. Predatory bugs preferred plants infested with spider mites to plants with thrips. Experience with spider mites on cucumber leaves prior to their release in the greenhouse had no effect on the preference of the predatory bugs. However, this experience did increase the percentage of predators recaptured. Y‐tube olfactometer experiments showed that O. laevigatus was more attracted to odours from plants infested with spider mites than to odours from clean plants. Thus, O. laevigatus is able to perceive odours and may use them to find plants with prey in more natural conditions. The consequences of the searching behaviour for pest control are discussed.
Sublethal effects of insecticides on the intrinsic rate of increase of cotton aphid
Authors: Kerns D.L. , Stewart S.D.
Published: October 2003

Insecticides are often implicated in causing outbreaks of the cotton aphid, Aphis gossypii (Glover) (Homoptera: Aphididae), through stimulation of reproduction. In this study we report the sublethal effects of dosages of bifenthrin, acephate, carbofuran or pyriproxifen on cotton aphid reproduction. We could not detect any increase or decrease in the intrinsic rate of increase of cotton aphids exposed to bifenthrin, acephate or carbofuran. However, we did detect some increases in the net reproductive rate of aphids treated with bifenthrin justifying further investigation of the effect on reproduction by this insecticide. Trends based on simple linear regression models suggest that sublethal dosages of bifenthrin or carbofuran have a negative impact on aphid population growth as dosages increase. These data suggest that stimulation of reproduction by these insecticides probably does not play a major role in cotton aphid outbreaks or resurgence. Pyriproxyfen is a juvenoid currently used for control of whiteflies in cotton. It demonstrated significant activity towards cotton aphid reared on treated cotton in our bioassays. Pyriproxyfen caused sterility in most aphids exposed to dosages exceeding 1 ppm, and reduced aphid longevity by approximately 50%. However, it did not appear to greatly influence the reproductive potential or longevity of reproductively mature aphids. A field study indicates that pyriproxyfen affects cotton aphid population structure and may have potential in managing cotton aphid outbreaks. Modifying aphid population structure and growth through the use of juvenoids such as pyriproxifen may prove to be an effective proactive approach to pest control without adversely impacting beneficial organisms or causing pest resurgence.
Learning used as a strategy for host stage location in an endophytic host‐parasitoid system
Authors: Dutton A. , Mattiacci L. , Dorn S.
Published: October 2003

The relationship between host stage selection and foraging behaviour of Pholetesor bicolor Nees (Hymenoptera: Braconidae), a larval parasitoid of Phyllonorycter spp. (Lepidoptera: Gracillariidae), was investigated under laboratory conditions. The endophytic host develops through two larval stages with different feeding habits, accordingly named sap‐ and tissue‐feeders. The parasitoid was able to find and parasitise both larval stages, even though it is most successful in parasitising the sap‐feeder stage. The influence of experience in the parasitoid's searching behaviour was observed in a choice bioassay. Searching activity increased when either contact experience with the sap‐ or the tissue‐feeder host was given. Furthermore, the ability of the parasitoid to locate a sap‐ or a tissue‐feeder infested plant was influenced by the type of experience given prior to the bioassay. Naive females were less active, and were observed with equal frequency on sap‐feeder, tissue‐feeder and non‐infested plants. In contrast, females that were given previous contact experience with sap‐feeders (i.e., the host stage which provided the most successful parasitism) were observed foraging more often on plants infested by the sap‐feeders, than on those infested by tissue‐feeders or on non‐infested plants. Experience with a tissue‐feeder host had no detectable effect on host stage location and only enhanced P. bicolor's foraging activity. The advantages of learning in this tritrophic system are discussed.
Sexual maturity and intraspecific mating success of two sibling species of the Bactrocera dorsalis complex
Authors: Wee Suk‐Ling , Tan Keng‐Hong
Published: October 2003

Bactrocera carambolae Drew & Hancock and B. papayae Drew & Hancock (Diptera: Tephritidae), two closely related sibling species in the B. dorsalis (Hendel) complex were shown to have different rates of sexual maturity. The response of B. carambolae males to methyl eugenol was observed to begin 10 days after emergence and increased with age. The attractancy peaked at 28 days after emergence and above. The males were also found to require a higher dosage of methyl eugenol (1 mg) for optimal response. These results are in contrast with those of B. papayae reported previously. The response to methyl eugenol was also observed to correspond with the age when first mating was performed.

After eclosion, both sexes of B. carambolae mated approximately 2 weeks later and showed significantly lower matings/individual when compared with B. papayae in a 60‐day observation period. Both sexes of B. papayae and males of B. carambolae were able to remate on the next day. However, B. carambolae females required a minimum refractory period of 8 days in order to be sexually receptive again.

During the 60‐day period, the mating propensity in B. papayae (100% success) was higher than B. carambolae (71–87% success) (P < 0.05). This observation was substantiated by a higher intraspecific mating success of B. papayae as compared to B. carambolae in a field cage (P < 0.001).
Egg production in response to combined alternative foods by the predator Coccinella transversalis
Authors: Evans Edward W.
Published: October 2003

Insect predators may commit to reproduction to varying degrees depending on the nature of the prey they consume. I compared egg production by females of the aphidophagous ladybird beetle Coccinella transversalis (F.) (Coccinellidae) maintained on differing diets. As expected, females laid most eggs on a diet of aphids (pea aphids, Acyrthosiphon pisum[Harris]). Upon being switched from a diet of aphids, females laid no eggs after the first 3 days when maintained on a water solution of sucrose, and laid almost no eggs when maintained on a diet of second‐instar larvae of the moth Helicoverpa armigera (Hübner). However, females laid eggs in small numbers (on average, 2.7 eggs per day) when provided both sucrose and Helicoverpa larvae. Females laid similar numbers of eggs when aphid honeydew was substituted for sucrose in combination with Helicoverpa larvae; in both cases, egg production was only 10–15% of that on a diet of aphids. The production of small numbers of eggs from consumption of non‐aphid foods may enhance the ability of aphidophagous ladybirds to optimize their timing of reproduction at short‐lived colonies of their preferred aphid prey.
The lethal effects of gamma irradiation on larvae of the Huhu beetle, Prionoplus reticularis: a potential quarantine treatment for New Zealand export pine trees
Authors: Lester Philip J. , Rogers David J. , Petry Robert J. , Connolly Patrick G. , Roberts Peter B.
Published: October 2003

Gamma irradiation was investigated as a possible method for disinfestation of huhu beetle larvae, Prionoplus reticularis White, in Pinus radiata D. Don. Larvae of four representative size classes were irradiated at six doses, and the lethal dose (LD99) calculated from mortality data 3 days and 10 days post treatment. All larval size classes showed a similar sensitivity to gamma irradiation and required 3677 Gray (Gy) and 2476 Gy for a LD99 3 and 10 days post‐treatment, respectively. The penetration of gamma irradiation into pine wood was found to be lowest in freshly cut logs, and decreased linearly at a rate of 0.698 Gy mm−1 of wood. The penetration was greatest in wood that had been stored for 2 years, and decreased 0.512 Gy mm−1 of wood. These results are likely to be correlated with wood moisture content. Gamma irradiation appears to be a potential alternative method to fumigation for quarantine treatment of P. reticularis.
Parasitism of the grasshopper Melanoplus sanguinipes by a sarcophagid fly, Blaesoxipha atlanis: influence of solitary and gregarious development on host and parasitoid
Authors: Danyk T. , Johnson D.L. , Mackauer M.
Published: October 2003

Blaesoxipha atlanis (Aldrich) (Diptera: Sarcophagidae) is a common parasitoid of the grasshopper Melanoplus sanguinipes (F.) (Orthoptera: Acrididae) in western Canada. We tested the hypothesis that B. atlanis can develop as either a solitary or a gregarious parasitoid, and assessed the influence of parasitism on the growth and survival of infected grasshoppers. Males and females of M. sanguinipes were parasitized manually with one, two, or three first‐instar larvae of B. atlanis in the laboratory. Parasitism was more deleterious to males than females of M. sanguinipes; females are larger than males. Host survival and longevity declined with the number of larvae per host in a sex‐specific manner. In females, 39%, 24%, and 8% of hosts containing, respectively, one, two, and three sarcophagid larvae survived parasitism. Although 41% of single‐parasitized males survived, all males containing more than one larva died. Variations in host quality as measured by dry mass explained much of the response to parasitism in male, but not female, hosts. Parasitoid larvae, apparently, did not cause significant physical damage to host organs and tissues but instead functioned as a metabolic sink. The greater metabolic activity associated with egg production could account for the relatively higher tolerance to parasitism of female, as opposed to male, grasshoppers. Developmental time, adult size, and percentage survival of B. atlanis declined with the intensity of parasitism, especially in parasitoids developing in male hosts. Females developing gregariously contained fewer ovarioles at eclosion than counterparts developing as solitary larvae. The mean body size of field‐collected B. atlanis did not differ from that of laboratory‐reared parasitoids developing singly in a host. Gregarious development is an alternative strategy to solitary development that may enable B. atlanis to maintain population numbers during periods of grasshopper scarcity.
15N‐marked aphids for predation studies under field conditions
Authors: Nienstedt K.M. , Poehling H.M.
Published: October 2003

Individuals ofSitobion avenae (F.) (Homoptera: Aphididae) were marked with the stable isotope 15N through feeding on cereal seedlings which were immersed in a15N‐enriched nutrient solution. Increased 15N‐contents were obtained in all aphids with no detrimental effect on survival and fertility. When 15N‐marked aphids were transferred to non 15N‐enriched seedlings, after a short initial decreasing phase, 15N‐contents remained nearly constant in time. A content of 10% 15N in the nutrient solution of the seedlings was sufficient for marking the aphids.
Effects of agricultural diversification on the abundance, distribution, and pest control potential of spiders: a review
Authors: Sunderland Keith , Samu Ferenc
Published: October 2003

A review of the literature showed that spider abundance was increased by diversification in 63% of studies. A comparison of diversification modes showed that spider abundance in the crop was increased in 33% of studies by ‘aggregated diversification’ (e.g. intercropping and non‐crop strips) and in 80% of studies by ‘interspersed diversification’ (e.g., undersowing, partial weediness, mulching and reduced tillage). It is suggested that spiders tend to remain in diversified patches and that extending the diversification throughout the whole crop (as in interspersed diversification) offers the best prospects for improving pest control. There is little evidence that spiders walk in significant numbers into fields from uncultivated field edges, but diversification at the landscape level serves to foster large multi‐species regional populations of spiders which are valuable as a source of aerial immigrants into newly planted crops. There are very few manipulative field studies where the impact of spiders on pests has been measured in diversified crops compared with undiversified controls. It is encouraging, however, that in those few studies an increased spider density resulted in improved pest control. Future work needs are identified.
Olfactory responses of two species of grasshoppers to plant odours
Authors: Chen H.H. , Kang L.
Published: October 2003

Electroantennogram (EAG) responses were recorded from two species of oedipodine grasshoppers, Oedaleus decorus asiaticus L. (graminivorous) and Angaracris barabensis Pall. (forbivorous), to volatiles emitted by chopped leaves of ten plant species. Male O. d. asiaticus showed much stronger EAG responses than conspecific females and both sexes of A. barabensis. Sexual differences in EAG responses correspond to different numbers of antennal sensilla of both sexes and to certain behavioural and morphological factors as well. The overall EAG response profiles of the two grasshopper species to the ten plant odours were similar. However, adaptation to host odour might have occurred because of differences in their feeding habits. Females of the graminivorous O. d. asiaticus possess a significantly higher olfactory sensitivity for poaceous plant species than A. barabensis, while the forbivorous A. barabensis showed significantly higher EAG responses to Allium senescens (Liliaceae), and a tendency of high responses to composite plant species in comparison with O. d. asiaticus.
Effects of crowding on populations of Aedes albifasciatus larvae under laboratory conditions
Authors: Gleiser Raquel M. , Urrutia Jorge , Gorla David E.
Published: October 2003

Aedes (Ochlerotatus) albifasciatus (Macquart 1838) (Diptera: Culicidae) is a neotropical flood water mosquito, incriminated as the main vector of the western equine encephalitis virus, and which affects beef and milk production in central Argentina. The short time required to hatch and develop from egg to adult, usually in temporary pools, suggests a strategy which allows for exploitation of transient pools, thus evading predation and interspecific competition. Under these conditions intra specific competition could represent a major density‐dependent source of larval mortality, but the relative importance of density‐dependent regulation of mosquito populations has generated controversy. Therefore we examined the effects of larval density on basic population characteristics of Ae. albifasciatus in the laboratory. Larvae were obtained by synchronous hatching of eggs laid by field‐trapped females. Emerging larvae (L1) were used to build cohorts of different initial densities, kept in plastic trays with 400 ml of distilled water, and food supplied daily during the first 10 days (0.1 g per larvae day−1). Age‐specific development time and specific and relative mortality were estimated, and their relation to initial larval density was assessed through linear and non‐linear regressions and correlation analysis. First hatching was registered 3 h after flooding the eggs. Higher levels of pre‐adult mortality were detected in groups with higher densities. Specific mortality and average time to enter a stage of L1 to L3 could directly be related to initial larval density, but no significant relations were found for L4 and pupae. Results suggest that crowding could be a factor capable of regulating the density of natural populations of Ae. albifasciatus.