bluuebunny/crossref_metadata_2025 huggingface dataset:
Toxicity of acephate to larvae of gypsy moth as a function of host plant and bioassay method
Authors: Moldenke Alison F. , Berry Ralph E. , Miller Jeffrey C. , Wernz James G.
Published: October 2003

We examined toxicity of acephate to third‐instar gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), under different conditions of administration method, availability of food to larvae during bioassay, host plant, and activity of detoxifying enzymes. Larvae that had been fed field‐collected foliage of white alder (Alnus rhombifolia Nutt.) were less susceptible 48 h after treatment with topically applied acephate if they were allowed to continue feeding on foliage during the bioassay period (LD50= 60.6 μg/g larva) than if they were not (LD50= 13.5 μg/g larva). All surviving larvae were replaced on their original food plant after the 48‐h bioassay; of these, 14.4% of the larvae not fed during treatment died before pupation, compared with 1.3% of the larvae fed alder during treatment. The LD50 obtained for topically treated larvae reared and treated on Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco, (51.1 μg/g larva) was comparable to that obtained for larvae fed alder (60.0 μg/g larva) throughout treatment. Larvae treated orally with acephate, however, were slightly more susceptible when reared on Douglas‐fir (LC50, 20.3 ppm) than when reared on alder (LC50, 27.0 ppm). Post‐treatment mortality in orally treated larvae was 10.3% in those fed alder and 9.5% in those fed Douglas‐fir. Higher cytochrome P‐450 activities in larvae reared on Douglas‐fir apparently did not enhance tolerance to acephate. Both sexes of orally treated larvae took significantly longer to pupate than did controls on both foliage types, as did topically treated males fed Douglas‐fir. Pupal weight generally was slightly, but not always significantly, higher in treated than untreated larvae under all dietary and treatment regimes.
A behavioural study to help clarify how undersowing with clover affects host‐plant selection by pest insects of brassica crops
Authors: Finch S. , Kienegger M.
Published: October 2003

Laboratory and field‐cage tests were done to determine how undersowing brassica plants (Brassica oleraceae L. and B. rapa L.) (Cruciferae) with subterranean clover (Trifolium subterraneum L.) (Papilionaceae) affected host‐plant selection by eight pest insect species of brassica crops. The pest species tested were Pieris rapae (Lepidoptera: Pieridae) (the small white butterfly), Pieris brassicae (Lepidoptera: Pieridae) (the large white butterfly), Delia radicum (Diptera: Anthomyiidae) (the cabbage root fly), Phaedon cochleariae (Coleoptera: Chrysomelidae) (the mustard beetle), Plutella xylostella (Lepidoptera: Yponomeutidae) (the diamond‐back moth), Evergestis forficalis (Lepidoptera: Pyralidae) (the garden‐pebble moth), Mamestra brassicae (Lepidoptera: Noctuidae) (the cabbage moth) and Brevicoryne brassicae (Hemiptera: Aphididae) (the cabbage aphid). In all tests, except two in which the brassica plants were about three times as high as the clover background, 39%–100% fewer of the pest insect stage monitored were found on host plants presented in clover than on those presented in bare soil. Contrary to claims supporting the ‘enemies hypothesis’, differences in colonization alone appeared sufficient to account for the lower numbers of insects found when host plants are undersown with clover. To be effective in reducing plant colonization, the clover must cover 50%, and preferably more, of the vertical profile of the crop plants. As clover used as an undersown crop often has to be cut to make it less competitive with the main brassica crop, temporal aspects of the condition of the clover during critical periods of pest activity need to be recorded carefully before concluding that undersowing does not produce the effect desired against certain pest species under field conditions. The effective clover barrier is like any other treatment, if it is not present at the appropriate time it cannot be expected to reduce pest insect numbers.
Oviposition of resistant and susceptible strains of Drosophila melanogaster in the presence of deltamethrin
Authors: Renou Michel , Henninot‐Rodes Emmanuelle , Delorme Robert , Augé Danielle , Touton Philippe
Published: October 2003

Oviposition of three strains of Drosophila melanogaster in the presence of deltamethrin was observed. These strains had different levels of physiological susceptibility to deltamethrin. Two‐choice tests were conducted with couples of flies in petri‐dish arenas containing two oviposition dishes. On the first day of the experiment, females were given a choice between a treated oviposition dish and an untreated control dish. On the second day of the experiment, two control oviposition dishes were given to females. Although individual females showed a tendency to aggregate their eggs in one of the dishes, control experiments demonstrated an overall equal distribution of eggs between the dishes. When one of the two oviposition dishes in the arena was treated with deltamethrin, the percentage of females ovipositing and the mean number of eggs laid by females were reduced, compared with control arenas. Females avoided the treated oviposition dish and laid significantly more eggs on the control dish. Furthermore, when the deltamethrin concentration was increased on the first day, female flies postponed their oviposition and laid significantly more eggs on the second day. The resistant strain, SR, demonstrated the same capacity to select the untreated site for oviposition as the susceptible strain, but it showed a smaller oviposition reduction and egg retention. The relationship between physiological and behavioural susceptibility to deltamethrin is discussed.
Response of the pollen beetle Meligethes aeneus to volatiles emitted by intact plants and conspecifics
Authors: Ruther Joachim , Thiemann Karsten
Published: October 2003

The response of the pollen beetle Meligethes aeneus Fab. (Coleoptera, Nitidulidae) to the volatiles of undamaged plants and conspecifics was tested in a Y‐tube‐olfactometer‐bioassay. Beetles that had hibernated preferred significantly the volatiles emitted by their most important host plant, oilseed‐rape (Brassica napus L. ‘Lorar’) in the early bud‐stage. However, the odour emitted by rye (Secale cereale L.), tomato plants (Solanum lycopersicum L.), and yarrow (Achillea millefolium L.) were also attractive when tested against the corresponding growing‐medium. Dock plants (Rumex obtusifolius L.) and touch‐me‐not (Impatiens parviflora L.) possessed no attractive properties. When tested against each other, oilseed‐rape was preferred significantly by M. aeneus above all other plants, with the exception of tomato. The results indicate that M. aeneus is able to locate its host plant by olfactory stimuli in the early bud‐stage, i.e. in that stage in which the infestation begins in the field and when the typical yellow colour and floral scent of oilseed‐rape are absent.

Female pollen beetles avoided significantly the volatiles emitted by female conspecifics and an ether extract of conspecifics of mixed sex, while volatiles from males had no significant effect on females. Furthermore, males showed no preferences when responding to conspecific odour in the olfactometer. These results suggest the existence of an epideictic pheromone for M. aeneus.
Obituary
Authors: Parella M.P.
Published: October 2003

We received the sad news that our Editor Dr Sean S. Duffey passed away unexpectedly on 21 May 1997. Dr Duffey has been serving the journal since 1994 with great enthusiasm. Many authors have profited from his positive criticisms, which were always accompanied by detailed suggestions as to how their manuscripts could be improved. Because of his thorough reviews of papers on various topics, Dr Duffey has made an outstanding contribution to the journal. Dr Duffey's views and helpfulness well be missed, not only by his family, friends and colleagues, but also by us and the readership of this journal. An Obituary for Dr Duffey by a close colleague is published below.

The Executive Editors
Distribution of faeces of the German cockroach, Blattella germanica, in a new refuge
Authors: Stejskal Václav
Published: October 2003

The patterns of faeces deposition in glass arenas with three groups of Blattella germanica L. during colonization of new refuges were recorded. The individual positions of more than 17,500 faeces were recorded. The average daily rate of faeces excretion per adult was 9.6 in males, 9.1 in non‐gravid females and 2.7 in gravid females. Significant differences of faeces accumulation at various sites of the arena were found. In all three groups, mean density of faeces decreased in the following order: shelter, edges of arena, area around shelter, remainder of open area. The faeces were not accumulated more significantly at food and water sources than within the remainder of the open area. Low concentrations of faeces around edges were recorded with gravid females. The ratio of numbers of faeces in the shelter and those on the remainder of the arena was nearly identical in all tested groups. The rate of faeces deposition fluctuated during colonization of a new refuge. The role of faeces containing aggregation pheromone and ammonia in the ecology and behaviour of B. germanica is discussed.
Behavioral responses of lightbrown apple moth neonate larvae on diets containing Bacillus thuringiensis formulations or endotoxins
Authors: Harris M. O. , Mafile'o F. , Dhana S.
Published: October 2003

Behavioral responses of individual lightbrown apple moth, Epiphyas postvittana (Walker), neonate larvae to Dipel or the Bacillus thuringiensis delta endotoxins CryIAc and CryIBa incorporated into artificial diets were measured in choice and no‐choice treatments. Frass production and the spinning of silken shelters were delayed when larvae were given diets containing Dipel or Bt endotoxins. In choice treatments larvae did not exhibit an initial preference for control diets over diets with Dipel or Bt endotoxins but accumulated on control diets over a period of days, apparently because larvae that first settled on Dipel or endotoxin diets abandoned diets while larvae that fed on control diets remained on diets throughout the experiment. Abandonment of diets containing Dipel or endotoxins was also apparent in no‐choice treatments. Larvae exposed to such diets were more likely to be observed walking or at different sites from one observation to the next, and produced frass and silken feeding shelters at multiple sites rather than a single site. The implications of these findings for the use of B. thuringiensis as a commercial spray or for the use of B. thuringiensis endotoxin genes as resistance factors to be expressed in transgenic apples are discussed.
Influence of plant structural complexity on the foraging success of Trichogramma minutum: a comparison of search on artificial and foliage models
Authors: Lukianchuk J. L. , Smith S. M.
Published: October 2003

The influence of structural complexity on the foraging success for host eggs (Ephestia kuehniella Zeller) by Trichogramma minutum Riley was investigated in the laboratory. Naive females were released into arenas with structurally different paper models or foliage (simple: trembling aspen Populus tremuloides Michx., complex: balsam fir Abies balsamea L.). Observations of individual females were made every 15 min and searching success was measured by the number of host egg clusters found and the amount of time taken to find them, within a period of 196 min. Females found significantly more egg clusters and were quicker at finding them on the sample paper and foliage surfaces than on the most complex paper or foliage surfaces. Older females (2–3 days) were more successful and searched quicker than younger (<24 h) females on all paper surfaces. The timed observations suggested that wasps which spent more time walking had a significantly decreased probability of finding an egg mass and were significantly slower at finding them. Females that spent more time on paper surfaces had an increased probability of finding an egg mass. The significance of searching differences is discussed in relation to the potential effects of plant surfaces on Trichogramma movements and to the physiological readiness of the wasp.
Toxicity of fipronil to German and American cockroaches
Authors: Kaakeh Walid , Reid Byron L. , Bennett Gary W.
Published: October 2003

Topical and oral toxicity of fipronil, compared to chlorpyrifos, was determined for the German cockroach, Blattella germanica (L.), and American cockroach, Periplaneta americana (L.). Fipronil and Combat bait matrices were evaluated for their attractancies to both species. In the topical toxicity tests, LD50's of fipronil, at 72 h after topical application, were 0.03 and 0.02 μg/g for adult B. germanica and P. americana, respectively. Fipronil was significantly more toxic than topically applied chlorpyrifos (LD50's were 0.06 and 0.16 μg/g for B. germanica and P. americana, respectively). The oral toxicity of fipronil and chlorpyrifos in Petri dish experiments, against both species, was affected by stage (for B. germanica), diet concentration, and feeding assay. Fipronil caused higher mortality of B. germanica than chlorpyrifos in two feeding assays (continuous and abbreviated). Both compounds were equally toxic to adult males of P. americana at all rates. Fipronil caused higher nymphal mortality than chlorpyrifos 48–72 h after exposure in both feeding assays. In large population chamber tests, fipronil bait was more effective and faster in killing P. americana than Raid and Combat. LT50's were 0.8, 2.4, and 7.6 d for fipronil, Raid (a.i. = chlorpyrifos), and Combat (a.i. = hydramethylnon) baits, respectively. Mortality reached 96.5, 93.4, and 84.6%, respectively, at the end of the 14 d test. In the bait attractancy tests, both strains of B. germanica were attracted similarly to fipronil and Combat bait matrices. P. americana were attracted more to fipronil than to Combat bait matrix or to other alternative foods.
Acceptability and suitability of seven plant species for the mealybug Phenacoccus parvus
Authors: Marohasy Jennifer
Published: October 2003

Survival, development and fecundity of cohorts of the mealybug Phenacoccus parvus Morrison were measured over one generation on seven plant species representing four plant families. Survival, development and fecundity were not significantly higher on the mealybug's principal field host, the weed Lantana camara L. (Verbenaceae), than on other plant species including Lycopersicon esculentum Miller (tomato) and Solanum melongena L. (eggplant). The acceptability of the leaves of the seven plant species to P. parvus first instar crawlers was measured on hatching, after active walking and after food deprivation. Lantana camara was the highest ranked plant species for all treatments. The number of crawlers settling on lower ranked plant species increased with the level of food deprivation.
Gypsy moth (Lymantria dispar) larval development and survival to pupation on diet plus extractables from green ash foliage
Authors: Markovic Ingrid , Norris Dale M. , Nordheim Erik V.
Published: October 2003

Gypsy moth, Lymantria dispar L., rate of larval development, molting, pupal weight and survival were studied on an artificial diet containing different concentrations of green ash ethyl acetate extractables (EtOAc Exts). Insects were reared on experimental diets from egg to pupa. Addition of EtOAc Exts to artificial diet significantly prolonged larval development and reduced their survival compared to larvae reared on control diet. Weights of pupae were significantly reduced when larvae were reared on diet containing the lowest dosage of EtOAc Exts (i.e., 0.01%) versus on control diet. EtOAc Exts in diet (e.g., 0.01, 0.06 and 0.2%) frequently caused incomplete ecdysis which invariably resulted in larval death. Impaired feeding, locomotion and excretion are likely causes of death. The combination of these results with our earlier findings of repellents and feeding deterrents against gypsy moth larvae (GML) in green ash foliage shows that the non‐host status of green ash to the highly polyphagous GML involves three orders of chemical defense: repellents, feeding deterrents and inhibitors of nutritional and developmental physiology. As the insect becomes sequentially exposed to these orders of defense, it incurs higher costs because the adverse effects become less reversible.
Inter‐ and intra‐population differences in the effects of temperature on postdiapause development of Delia radicum
Authors: Turnock W. J. , Boivin G.
Published: October 2003

Canadian populations of D. radicum differ in their response to temperature during postdiapause development. Populations that are primarily of the early‐emerging type (≤256 DD04) (St‐Jean, Quebec; London, Ontario) have high values for the parameters describing this response: Rm= 12.7–13.3; Tm= 28.0–31.8 °C; Tσ= 10.3–14.2 (Rm, the maximum developmental rate at the temperature, Tm [ °C ] where the developmental rate is highest, and Tσ, the parameter which gives the shape of the truncated normal curve fitted to the data), a low degree‐day requirement for emergence (160–232 DD04), and may lack a developmental delay at temperatures above ca. 21 °C. Populations of the late‐emerging type (Kildare, Prince Edward Island) have low parameter values (Rm= 2.5, Tm= 19.3 °C; Tσ= 6.4), high degree‐day requirements (530 DD04), and a developmental delay at high temperatures. The parameters for the early‐emergers in the population from Winnipeg, Manitoba (74% early) were intermediate (Rm= 9.1, Tm= 27.1 °C, Tσ= 10.7, DD04= 246), but resembled the early rather than the late type. This population varied from 31 to 90% early type over a 10‐year period and the rate of postdiapause development at 20 °C was directly related to the percentage early. In the year with the most rapid development (90% early), development was significantly slower than in the populations from other locations with predominantly early populations, and the year with the slowest development (31% early) showed significantly faster development than that from Kildare, Prince Edward Island (100% late). Therefore the parameters for early and late types of development will not be accurate for use in mixed populations, and the parameters in mixed populations will change among years. Populations of D. radicum in North America and Europe (67 locations by years) varied from 0–100% early. At Winnipeg, the percentage early was directly related to the annual temperature accumulation (DD05) during the growing season. The calculation of developmental parameters for the early‐emergers of mixed populations provides a more accurate basis for estimating the times of first emergence and the first peak of emergence than parameters based on the whole population. Since postdiapause developmental rates vary both among and annually within locations, developmental models should be designed to include such variations.
Sequential sampling for adult coccinellids in wheat
Authors: Elliot N. C. , Michels G. J. , Kieckhefer R. W. , French B. W.
Published: October 2003

Adult aphidophagous coccinellids are important predators of cereal aphids in wheat in the Great Plains of the United States for which sampling methods are needed to facilitate improved management. An equation relating the mean number of adult coccinellids per m2 in a wheat field to its variance was obtained using Taylor's power law. A sequential sampling procedure was developed to estimate the number of adult coccinellids per m2 with constant average statistical precision (standard error/mean). The procedure was constructed by an equation relating the number of adult coccinellids per m2 to the number of adult coccinellids per minute of counting incorporating into the Taylor's power law relationship. The procedure involves conducting a series of 1‐min counts while walking through a field at a constant velocity of 10 m per minute. After each 1‐min count sequential sampling stop‐lines are consulted to determine if the specified level of precision has been achieved. Two methods, a statistical procedure and comparison with independent data, were used to assess the consistency with which the specified level of precision was achieved by the procedure. Results indicated that observed precision was close to that specified by the user over a wide range of adult coccinellid density.
Nematode parasitism in a northern European drosophilid community
Authors: Gillis Jaklien E.M. , Hardy Ian C.W.
Published: October 2003

Many factors may influence the structure of invertebrate communities. Among these is the presence of parasites which attack some or all members of a guild and potentially promote coexistence of competitor species. We assessed the prevalence of nematode (Allantonematidae) parasitism in Dutch woodland drosophilids (Diptera). Nematodes were found in 6 of the 18 drosophilid species sampled (percentage parasitism in parentheses): Drosophila phalerata (16%), D. kuntzei (5.1%), D. immigrans (0.5%), D. testacea (1.2%) and D. transversa (2.8%) were all parasitized by Howardula aoronymphium and D. subobscura (3%) was parasitized by Parazitylenchus diplogenus. This is the first report of nematode parasitism of D. immigrans and D. transversa. There were no important seasonal trends in percentage parasitism. We explored the consequences of nematode parasitism for individual drosophilids. Nematodes did not exert an important influence on the wing length (adult body size) of the drosophilids we sampled, but egg loads (fecundities) of female D. phalerata, D. subobscura and D. kuntzei were reduced by nematode parasitism. Parasitism rates were positively correlated with relative host abundance, in Dutch and other communities, suggesting that species diversity is promoted by a disproportionately high parasitism of more common host species.
Behavioral cues associated with oviposition by Trioza eugeniae
Authors: Luft Patrick A. , Paine Timothy D.
Published: October 2003

Trioza eugeniae oviposited significantly more eggs on Syzygium paniculatum leaves free of eggs compared to leaves with pre‐existing eggs in a choice experiment, suggesting that females modify oviposition based on cues associated with the presence of eggs. In separate experiments, females avoided ovipositing on parts of leaves where eggs were present, but readily oviposited on areas of the same leaf without eggs. Epideictic pheromones are apparently not used by this species because females readily oviposited on areas of a leaf from which eggs had previously been removed. Females laid 57% of all their eggs along the margins of normal leaves, but also oviposited on artificial margins produced by cutting the leaves. The preference for natural margins over artificial margins was eliminated when the entire margin was coated with an antitranspirant compound to mask the damaged edge. These studies show that ovipositing psyllids respond both to the presence of eggs and to the suitability of the substrate.
Oviposition patterns of the pine weevil Hylobius abietis
Authors: Nordlander Göran , Nordenhem Henrik , Bylund Helena
Published: October 2003

Spatial and temporal distributions of eggs laid by the pine weevil Hylobius abietis (L.) (Coleoptera: Curculionidae) were studied by taking root and soil samples around pine stumps on a clear‐cutting in central Sweden. In addition, first‐instar larvae migrating in the soil were sampled using traps baited with host‐odour. Eggs were found in the soil rather than in the bark of stump roots, which previously has been regarded as the usual oviposition site. Based on an oviposition experiment and additional field observations we conclude that eggs are laid in the bark of roots only when the surrounding material is likely to dry out. We suggest two explanations for why weevils oviposit mainly in the soil, although they are known to show stereotypic behaviour when inserting eggs in stump roots: (1) egg predation by other arthropods or by conspecifics is avoided, and (2) newly hatched pine weevil larvae are better than ovipositing females at locating suitable sites for larval feeding.
Diapause avoidance induced by low temperature in the yellow‐spotted longicorn beetle, Psacothea hilaris
Authors: Shintani Yoshinori , Ishikawa Yukio
Published: October 2003

The diapause‐averting effect of low temperature on pre‐diapause larvae was examined in the yellow‐spotted longicorn beetle, Psacothea hilaris. Larvae that had been reared under diapause‐inducing conditions (25 °C, L12:D12) were temporarily exposed to 10 °C for various periods, and returned to the initial condition. Diapause was not averted by chilling for 15 days irrespective of the age of the larvae at chilling. After a 30‐day chilling treatment, all of the 40‐ and 60‐day‐old larvae averted diapause, while diapause was averted in only one‐third of the 10‐ and 20‐day‐old larvae. None of the pre‐diapause larvae chilled for 60 days entered diapause irrespective of the age at chilling. With diapause avoidance, larvae that overwintered in earlier instars can start growing in earliest spring without any arrest; this phenomenon probably subserves the synchronization of larval development in a population.
Melon resistance to the aphid Aphis gossypii: behavioural analysis and chemical correlations with nitrogenous compounds
Authors: Chen Jian Q. , Rahbé Yvan , Delobel Bernard , Sauvion Nicolas , Guillaud Josette , Febvay Gérard
Published: October 2003

In the melon, the Vat (monogenic, dominant) resistance gene governs both an antixenotic reaction to the melon aphid Aphis gossypii Glover (Homoptera, Aphididae) and a resistance to non‐persistent virus transmission, restricted to this vector species. We investigated the behavioural features and tissue localisation of the antixenosis resistance by the electrical penetration graph technique (EPG, DC system). We also compared the chemical composition in amino compounds and proteins of the phloem sap collected from two isogenic lines of melon (Cucumis melo L.), carrying the Vat gene or not. All behavioural and chemical data indicated that this resistance is constitutive. EPG analysis clearly showed that access to phloem, although delayed by alterations in pathway activities, was not impaired in terms of frequency of access or initiation of feeding. The most striking feature was, however, a very reduced duration of ingestion from phloem of resistant plants, making this compartment one of the tissues where the effects of the Vat gene are unambiguously expressed. This was confirmed by clear differential activity of phloem extracts in artificial no‐choice bioassays. Chemical analyses have shown that phloem saps from the two isogenic lines were extremely similar in profiles of ninhydrin positive compounds, and contained a low total amount of free amino acids (less than 10 mM). Out of more than 40 distinguishable peaks in the chromatograms (protein and non‐protein amino acids, as well as small peptides), only five differentiated the two genotypes. Two of them were increased in the resistant genotype: glutamic acid and a major unknown peak, probably a non‐protein amino acid (different from β pyrazolyl‐alanine, a Cucumis‐specific amino acid). The three others were depressed in resistant plants, and included the sulphur amino acid cystine and a peptide peak partly composed of the cysteine‐containing peptide glutathione (reduced form). Sap collection also showed that phloem exudation rates, as well as total protein and glutathione levels, were depressed in phloem sap from resistant plants. Such data are all indicative of a modified phloem‐sealing physiology, linked to sulfhydryl oxidation processes, in plants carrying the Vat gene. The originality of the mechanism of Vat resistance to aphids is discussed.
Plant compensation, natural biological control, and herbivory by Aphis gossypii on pre‐reproductive cotton: the anatomy of a non‐pest
Authors: Rosenheim Jay A. , Wilhoit Lawrence R. , Goodell Peter B. , Grafton‐Cardwell Elizabeth E. , Leigh Thomas F.
Published: October 2003

Crop plant compensation for herbivory and the population dynamics of herbivores are two key elements in defining an herbivore's pest status. We studied the dynamics of natural, unmanipulated populations of the aphid Aphis gossypii on seedling plantings of cotton, Gossypium hirsutum and Gossypium barbadense, over a 4‐year period in California's Central Valley. Aphid populations colonized all plantings, but reached densities in excess of 0.5 aphids/leaf during only one year (1991), when outbreaks occurred. Outbreak populations were, however, ephemeral; predation and parasitism suppressed aphid populations prior to the initiation of flower bud production, when cotton plant growth may become photosynthate‐limited. Effective natural biological control was observed despite the action of hyperparasitoids and the heavy mortality of immature parasitoids that occurred when predators consumed parasitized aphids.

We conducted manipulative experiments during 1991 and 1992 to quantify the ability of pre‐reproductive G. hirsutum to compensate for aphid herbivory. In 1991 aphid populations in the high‐damage treatment reached densities as high as any observed naturally during the past 37 years. Damage symptoms were severe: leaf area was reduced by up to 58% and total above‐ground plant biomass was reduced by 45%. By the time of crop harvest, however, plants had compensated fully for the early damage in each of the three traits that define cotton's economic value: the timing of crop maturation, the yield of cotton fiber, and the quality of cotton fiber. Aphid feeding damage did, however, produce some changes in plant architecture that persisted throughout the growing season, including a decrease in the number of vegetative branches. In 1992 aphid populations and associated damage were much lighter, but the qualitative responses to herbivory were consistent with those observed in 1991. Plant compensation for early damage was complete for economically significant measures, and vegetative branch production was again suppressed in mature cotton plants. There was no evidence for a change in the suitability of G. hirsutum as a host plant for A. gossypii as a result of early damage (‘induced resistance’).

We conclude that pre‐reproductive G. hirsutum, which has not yet begun strong allocations to reproductive structures or established architectural complexity, has retained effective means of compensating for herbivory. In contrast to other systems exhibiting strong compensation, G. hirsutum appears to compensate in part by enhancing apical dominance. The recognition of early‐season A. gossypii as non‐pests is critical to the sustainability of cotton production, because it will allow growers to forego pesticide applications that accelerate the evolution of pesticide‐resistance and disrupt natural communities of predators and parasitoids.
Biological control by two exotic parasitoids: eight‐year population dynamics and life tables of the arrowhead scale
Authors: Itioka Takao , Inoue Tamiji , Matsumoto Takashi , Ishida Norio
Published: October 2003

To determine the process of regulation of Unaspis yanonensis (Kuwana) (Hemiptera: Diaspididae) by the two introduced parasitoids, Aphytis yanonensis DeBach et Rosen and Coccobius fulvus (Compere et Annecke) (Hymenoptera: Aphelinidae), the temporal changes in the population density of U. yanonensis as well as the parasitism rates were monitored for eight years before and after the release of the two parasitoids in a Satsuma mandarin orange (Citrus unshiu Marc. (Rutaceae)) orchard. From 2–4 years after the release, the parasitism rate by C. fulvus gradually increased, eventually reaching 70%, while that by A. yanonensis showed a weak increase, remaining under 12%. During this period, the host density decreased to about 1/100 of the initial density. After the drastic decrease, the host density remained under 1/60 of the level previous to the release for at least 2 years with the populations of both parasitoids persisting. To estimate the ability of the two parasitoids to regulate the populations of U. yanonensis, life tables of U. yanonensis under natural conditions and predator/parasitoid‐exclusion (bagged) conditions were compared. It was demonstrated that C. fulvus and A. yanonensis impose about 70% mortality rate on the host at mature adult stages and about 30% on the host at immature adult stages. The results have strongly confirmed the high capability of the two parasitoids as biological control agents for U. yanonensis, which was suggested by earlier studies. However, contrary to those studies, the present study did not support the complementarity of the two parasitoids in regulating the host population, suggesting that the effectiveness of C. fulvus alone in regulating the host population at low levels.
Low‐vacuum electron microscopy of carabid chemoreceptors: a new tool for the identification of live and valuable museum specimens
Authors: Symondson W. O. C. , Williams I. B.
Published: October 2003

High‐vacuum scanning electron microscopy, following coating of specimens with gold, produces high quality images that have proved invaluable for the study of insect sensilla. Unfortunately, the technique is essentially destructive, and cannot be used on live or valuable museum specimens. In particular, high‐vacuum scanning usually causes the collapse of the tips of the palps, interfering with any examination of the sensilla in this area. A new low‐vacuum technique is described that avoids these problems. Insect cuticle does not need to be coated with gold, thus avoiding damage to important specimens. Examples are given of scans of the palp tips of live carabid beetles, anaesthetised with CO2. It was shown that the technique could consistently display these tips in their natural convex state. In all, four types of sensilla were identified by low‐vacuum scans of the maxillary palps, and four further types on the terminal segment of the antennae, plus glandular openings. The antennae revealed a type of sensilla that has not previously been described on carabids. These sensilla showed clear structural differences between the two species studied, Pterostichus melanarius Illiger and P. niger Schaller (Coleoptera: Carabidae), and can be used as a diagnostic character for both fresh and dried specimens. The low‐vacuum technique can be recommended for examining valuable ‘type’ specimens without risk of damage.
Development of pheromone traps for control and monitoring of sweetpotato weevils, Cylas puncticollis and C. brunneus, in Uganda
Authors: Smit N. E. J. M. , Downham M. C. A. , Odongo B. , Hall D. R. , Laboke P. O.
Published: October 2003

Experiments were carried out in Uganda to optimise pheromone traps for the African sweetpotato weevil species, Cylas puncticollis Bohe. and C. brunneus F. (Coleoptera: Apionidae). Various designs of funnel, water and sticky traps were compared and a 5‐l plastic jerry can trap was the most appropriate design for effectiveness and practicability. A solution of Omo detergent in water was found to be the most effective trapping agent. Fewer weevils were caught in red traps than in yellow, white, green or blue traps. Catches of C. puncticollis increased when the trap was raised above crop height, but catches of C. brunneus were unaffected. When marked weevils were dropped onto the trap, 36% of C. puncticollis and 23% of C. brunneus were captured, and, of weevils placed in the trap, 88% and 92%, respectively, of the two species remained overnight. Lures for the two species showed no significant loss in attractiveness after 8 weeks in the field, and chemical analysis showed 19% of the C. puncticollis pheromone and 72% of the C. brunneus pheromone remaining after this time. Summarizing, the following trap is presently recommended for monitoring/controlling African Cylas species: a 5‐l plastic jerry can trap of any colour with rectangular openings of 11×5 and 6×5 cm positioned 15 cm above the crop canopy, filled with 0.5 l Omo solution (1 g/1 l water), with 0.1 mg lures to be replaced every 8 weeks.
Evaluation of environmental and plant‐associated cues for nymphal settling preference by Trioza eugeniae
Authors: Luft Patrick A. , Paine Timothy D.
Published: October 2003

Experiments were conducted to determine potential cues used by nymphs when they select the preferred abaxial side of a leaf. Nymphs most frequently settle and develop on the abaxial side of leaves. The degree of preference for the abaxial side was found to be reduced when a high density of nymphs were present, however. The orientation of leaves in a completely darkened chamber did not influence settling preference for the abaxial side, even when leaves were oriented abaxial side up. Coating both sides of a leaf with an antitranspirant compound did not prevent nymphs from preferring the abaxial side for settling. Similar results were obtained when leaves were dipped in pentane. These studies show that nymphs do not use gravity, color, light, or contact chemoreception when selecting suitable settling sites on a leaf.
Comparative life table statistics of Apoanagyrus lopezi reared on the cassava mealybug Phenacoccus manihoti fed on four host plants
Authors: Souissi R. , Le Rü B.
Published: October 2003

The demographic statistics of Apoanagyrus lopezi De Santis (Hymenoptera: Encyrtidae) were studied in the laboratory on its host, the cassava mealybug Phenacoccus manihoti Matile‐Ferrero (Homoptera: Pseudococcidae), reared on four host plants characterized by different levels of antibiotic resistance to the mealybug: two cassava varieties, Incoza and Zanaga (Manihot esculenta Crantz: Euphorbiaceae), the faux‐caoutchouc (hybrid of M. esculenta×M. glaziovii Muel. Arg.) and Talinum (Talinum triangulare Jack:Portulacaceae).

Total and daily mean fecundities of female parasitoids were strongly influenced by the host plant but there was no link with antibiotic resistance. The mean duration of the oviposition period was also significantly modified by the host plant and was again not correlated to the level of antibiotic resistance. Net reproduction rates of female parasitoids were nearly 2 times higher on hosts fed on Zanaga and Talinum than on Incoza and Faux‐caoutchouc, and were not related to the total fecundities. The generation time was significantly longer on Faux‐caoutchouc than on the other three plants. The intrinsic rate of increase varied significantly with host plants and was higher on Talinum and Zanaga than on Incoza and Faux‐caoutchouc. With the varieties of cassava, Incoza and Zanaga, it was observed that antibiosis had a significant negative effect on the survival of A. lopezi, which would influence the effectiveness of the parasitoid.
The relative importance of glucosinolates and amino acids to the development of two aphid pests Brevicoryne brassicae and Myzus persicae on wild and cultivated brassica species
Authors: Cole R. A.
Published: October 2003

This paper describes an experiment to investigate the relative importance of glucosinolates and the availability of free amino acids in the phloem to the feeding behaviour and development of the specialist brassica aphid, Brevicoryne brassicae (L) (cabbage aphid) and the generalist, Myzus persicae, (Sultzer) (peach potato aphid). Aphid development was determined on brassica species and cultivated brassica varieties. Analysis of individual glucosinolates in the wild brassica species identified significant differences in their profiles and in their concentrations present in freeze dried leaves. Multiple regression analysis showed a significant correlation (r = 0.83) between the intrinsic rate of increase of B. brassicae and glucosinolate concentrations; four glucosinolates, 2‐OH‐3‐butenyl, and 2‐propenylglucosinolate, 3‐methoxyindolyl and 4‐pentenylglucosinolates accounted for 79% of the variation. The intrinsic rate of increase of M. persicae was less correlated, though still significant (r = 0.5); 3‐indolyglucosinolate and 3‐butenylglucosinolate accounted for 47% of the variation. Regression analysis also showed a correlation between phloem amino acid concentrations and the intrinsic rate of increase of B. brassicae (r = 0.48) but not of M. persicae. The concentration of the important amino acids tyrosine, alanine, leucine and glutamic acid, accounted for 43% of the variation in intrinsic rate of increase. Leaf water potential of the Brassica species showed no relationship with the intrinsic rate of increase of either B. brassicae or M. persicae.
Comparison of feeding behaviour of two Brassica pests Brevicoryne brassicae and Myzus persicae on wild and cultivated brassica species
Authors: Cole R. A.
Published: October 2003

Feeding behaviour of the specialist Brassicae aphid, Brevicoryne brassicae (L) (cabbage aphid) and the generalist, Myzus persicae, (Sulzer) (peach potato aphid) was monitored electronically on the susceptible cauliflower, Brassica oleracea var. botrytis cv Newton Seale, and a range of 17 Brassica species, B. carinata, B. juncea, B. nigra, B. macrocarpa, and B. villosa var. drepanensis and cultivated brassica varieties, B. oleracea, B. campestris and B. napus. Aphids, monitored for 10 h on the underside of leaves, performed recognisable feeding behaviour on all brassica species. The main differences in feeding behaviour, between M. persicae and B. brassicae, on the susceptible cauliflower Newton Seale, were fewer probes, shorter times to initially reach the phloem but longer times to establish sustained phloem ingestion and the longer times spent, by M. persicae, in xylem ingestion.

Feeding behaviour on the range of brassica species tested indicated that generalist and specialist aphids are influenced differently by the host plant. A longer time spent in xylem ingestion was again the major difference in the feeding behaviour of the two aphids. In addition, rejection of passive phloem ingestion, by M. persicae, was not related so closely to increased time spent in non probing activities, as for B. brassicae. This observation indicates that M. persicae does not generally accept or reject brassica species due to the presence of phagostimulants, such as glucosinolates at the leaf surface or along the stylet pathway, unless the concentration is very high. Differences in feeding strategies employed by generalist and specialist aphids on the same plants are discussed.
Changes of species specific cuticular hydrocarbon profiles in the cockroaches Nauphoeta cinerea and Leucophaea maderae reared in heterospecific groups
Authors: Everaerts Cl. , Farine J. P. , Brossut R.
Published: October 2003

The cuticular hydrocarbon profiles of the cockroaches Nauphoeta cinerea and Leucophaea maderae are species‐specific when maintained in homospecific rearings. When individuals were reared in mixed species colonies, they initially remained in homospecific groups under different shelters. However, after 14 days they formed one heterospecific group with cuticular profiles showing characteristics of both species. When individuals were returned in monospecific rearings, their cuticular hydrocarbon profiles returned to species‐specific ones within 3 weeks.
Voracity and feeding preferences of two aphidophagous coccinellids on Aphis citricola and Tetranychus urticae
Authors: Lucas Éric , Coderre Daniel , Vincent Charles
Published: October 2003

Voracity and feeding preferences of adult Coccinella septempunctata L. and Harmonia axyridis Pallas (Coleoptera: Coccinellidae, tribe Coccinellini) were evaluated in the laboratory on a common prey, the spirea aphid, Aphis citricola van der Goot (Homoptera: Aphididae), and on the twospotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), a prey previously unrecorded for these two predators. The experiments were carried out in the laboratory on apple saplings (Malus domestica Borkhausen). Adult males and females of H. axyridis consumed significantly more mites than adults of C. septempunctata. For H. axyridis, males consumed 41.3 spider mites in 24 h and females 48.4, whereas for C. septempunctata males consumed 14.1 prey and females 15.2. The consumption of spirea aphids by the males was similar for the two species. Consumption by the females was significantly greater for H. axyridis (46.5) than for C. septempunctata (22.2). The two coccinellids showed a significant preference for A. citricola in the presence of T. urticae. This preference was more pronounced for C. septempunctata. The total number of prey consumed and the percentage of exploited biomass decreased significantly for C. septempunctata and stayed relatively constant for H. axyridis as the number of mites increased in the prey ratio. Our results suggest that T. urticae is only an alternative prey for both predators, and that H. axyridis should be more efficient than C. septempunctata in a prey assemblage with aphids and mites.
Host locating behaviour of Leschenaultia exul and Patelloa pachypyga: two tachinid parasitoids of the forest tent caterpillar, Malacosoma disstria
Authors: Mondor Edward B. , Roland Jens
Published: October 2003

Leschenaultia exul (Townsend) and Patelloa pachypyga (Aldrich & Webber) (Diptera: Tachinidae) are the principal larval parasitoids of the forest tent caterpillar (FTC) Malacosoma disstria (Hübner) (Lepidoptera: Lasiocampidae) in Canada. The response of these two fly species to M. disstria differs depending on the tree species on which the host feeds. In wind tunnel experiments, L. exul spent more time on the side of the tunnel containing volatiles from FTC frass and was attracted to the FTC‐aspen poplar (Populus tremuloides Michx.) complex preferentially to the FTC‐balsam poplar (Populus balsamifera L.) complex. Field bioassays confirmed that this fly species was preferentially attracted to the herbivore‐aspen poplar complex as compared to the herbivore‐balsam poplar complex. In field bioassays, P. pachypyga was also attracted preferentially to aspen poplar trees containing FTC larvae, compared to balsam poplar trees with host larvae.
Heritability of flight distance for Cydia pomonella
Authors: Schumacher Peter , Weber Donald C. , Hagger Christian , Dorn Silvia
Published: October 2003

Cydia pomonella L. (Lepidoptera: Tortricidae) is considered to be rather sedentary, but some individuals undertake flights of several kilometres in the field. This paper investigates the genetic influence on this variability. The flight capacity was measured in the laboratory by a flight mill and its heritability was estimated for two different strains. The laboratory strain was kept for more than 45 generations and the field strain from Embrach (northern Switzerland) was recently collected in the field.

The multiple‐trait‐restricted‐maximum‐likelihood method was used for the estimation of genetic variances and covariances. A mixed full‐sib/half‐sib design was applied for the field strain and a full‐sib design for the laboratory strain. The heritability of total distance was 0.57 for the field strain and 0.37 for the laboratory strain (both sexes). In addition, a heritability of 0.38 for total distance was estimated by parent‐offspring regression for the laboratory strain. All three values were significantly different from zero (P<0.05) and show that there is a significant additive genetic influence on flight capacity.

The genetic correlations between total distance and other flight traits (total duration, flight velocity, longest flight) were between 0.84 and 1.00 for both strains and suggest that these traits actually belong to a single one. High genetic correlations were also found between total distance and the morphological traits body weight and wing length for the field strain, whereas a negative correlation was found between total flight distance and body weight for the laboratory strain. This difference between the two strains was interpreted as a possible trade‐off between flight capacity and fecundity.