bluuebunny/crossref_metadata_2025 huggingface dataset:
Oviposition behavior of Anastrepha fraterculus in apple and diel pattern of activities in an apple orchard in Brazil
Authors: Sugayama Regina L. , Branco Elisabete S. , Malavasi Aldo , Kovaleski Adalecio , Nora Ildelbrando
Published: October 2003

The oviposition behavior and diel pattern of activities of Anastrepha fraterculus (Wied.) (Diptera: Tephritidae) were observed in an apple orchard and fruit characteristics involved in oviposition preferences were investigated in field cage tests. Fruit size influenced fruit acceptability as an oviposition site by females which did not discriminate among the cultivars ‘Gala’, ‘Fuji’, and ‘Golden Delicious’ when same‐size fruits were presented simultaneously. Oviposition behavior in apples was basically the same as that described for primary hosts. Hourly census of fly activity indicated that adults did not overnight in the orchard and that they entered the orchard around 1100 h when temperature reached about 21 °C. Bird droppings were an important food item for adults. Behavioral differences between males and females might account for a significant biased sex ratio both in the orchard and at the edge of the native surrounding vegetation. Implications for fruit fly management in Brazilian apple orchards are discussed.
Dropping of pea aphids from feeding site: a consequence of parasitism by the wasp, Monoctonus paulensis
Authors: Chau Amanda , Mackauer Manfred
Published: October 2003

We examined the dropping behaviour of the pea aphid, Acyrthosiphon pisum (Harris), feeding on broad‐bean plants in the laboratory. Aphid responses to foraging and oviposition by females of Monoctonus paulensis (Ashmead) were instar‐specific and included kicking with the hind legs, walking away and dropping from the feeding site. Fourth nymphal instars were most likely to drop, followed by second, third, and first instars, in that order. Compared with first instars, the odds that a fourth‐instar aphid will drop were 6‐times higher independent of the stimulus, and 16‐times higher after parasitoid attack. Dropping from the feeding site increases an aphid's mortality risk. If parasitoid offspring are more likely to survive in small pea aphids, it may be adaptive for M. paulensis to choose smaller hosts, regardless of possible fitness gains due to increased body size from development in larger aphids.
Sublethal effects of Bacillus thuringiensis on the spruce budworm, Choristoneura fumiferana
Authors: Pedersen Anita , Dedes John , Gauthier Debbie , van Frankenhuyzen Kees
Published: October 2003

Exposing larvae of the spruce budworm, Choristoneura fumiferana (Clemens), to sublethal (≤ 50% lethal dose) levels of Bacillus thuringiensis subsp. kurstaki at various stages of their development significantly increased development time to the pupal stage and reduced pupal size and number of eggs laid per female, but did not affect the proportion of embryonated eggs. The changes in larval development time, pupal weight and fecundity depended on the larval stage that was treated. Exposure of fourth instars delayed larval development and reduced only male pupal weights with no effects on fecundity. Exposure of sixth instars delayed larval development to a lesser extent than exposure of fourth instars but had a pronounced effect on weight of both male and female pupae. The effect on pupal weight was sex dependent, as males tended to be more affected than females. The reduction in male pupal weight did not appear to influence fecundity, because the effect of exposure was explained by the change in female pupal weight. Effects on larval growth and pupal weight were proportional to the dose that was ingested during exposure, and were observed at doses as low as one‐tenth of the LD50. Ingestion of an LD50 caused a 29 or 45% delay in development of, respectively, female or male larvae when exposed as fourth instars and a 30% reduction in female pupal weight when larvae were exposed as sixth instars.
The effects of ingested ecdysteroid agonists (20‐hydroxyecdysone, RH5849 and RH5992) and an ecdysteroid antagonist (cucurbitacin B) on larval development of two polyphagous lepidopterans (Acherontia atropos and Lacanobia oleracea)
Authors: Blackford Michaela , Dinan Laurence
Published: October 2003

Larvae of two polyphagous lepidopteran species, Lacanobia oleracea (Tomato moth) and Acherontia atropos (Death's head hawkmoth), have been treated with representatives of three classes of compounds which are known to interact with the ligand binding site of insect steroid hormone receptors: a steroidal ecdysteroid (20‐hydroxyecdysone; 20E; agonist), two non‐steroidal dibenzoylhydrazines (RH5849 and RH5992; agonists) and the triterpenoid cucurbitacin B (cucB; antagonist). Both species are unaffected by dietary 20E at concentrations up to 400 ppm. L. oleracea metabolises ingested [3H]20E to a mixture of C‐22 fatty acyl esters, while A. atropos excretes [3H]20E unmetabolised. Both species are susceptible to the dibenzoylhydrazines when these are incorporated into the diet, with RH5992 proving lethal at 1 ppm and RH5849 proving lethal at 10 ppm. Thus, the metabolic/excretion mechanisms which are so effective against ingested 20E do not recognise the non‐steroidal agonists. The two species showed varying degrees of tolerance to cucB; L. oleracea was unaffected by 400 ppm in the diet, while A. atropos showed effects at 400 ppm, but not at 40 ppm. Feeding cucB in conjunction with 20E or injecting cucB when the ecdysteroid titre was low or rising also had no effect in L. oleracea. It is suggested that tolerance to the two classes of natural products (ecdysteroids and cucurbitacins) is associated with the occurrence of these compounds in some of the host plants of these species; evidence is presented for the presence of phytoecdysteroids in the host plants.
Host selection and sex allocation in Leptomastidea abnormis, a parasitoid of the citrus mealybug Planococcus citri
Authors: Cadée Niels , van Alphen Jacques J.M.
Published: October 2003

Leptomastidea abnormis (Girault) and Leptomastix dactylopii (Howard) [Hymenoptera: Encyrtidae] are the two parasitoid species frequently used for biological control of the citrus mealybug Planococcus citri (Risso) [Homoptera: Pseudococcidae]. As part of a programme to determine the best control practice, host size selection and sex allocation were studied in L. abnormis, and compared with those of L. dactylopii. L. abnormis showed a preference for the second size class, but also attacked third and fourth size class and adult mealybugs, while in previous studies L. dactylopii was found to prefer the third and fourth size class and adults, and never attacked second size class mealybugs. Female L. abnormis reared from parasitized mealybugs had a higher mean body mass than males, as is predicted by Charnov's theory on sex allocation. However, sex ratios of emerging L. abnormis did not differ between mealybug size classes. These results imply possibile coexistence of the two parasitoids. As field evidence suggests a more complex interaction between the two species, studying direct competition would be a useful next step.
Willow hybridization differentially affects preference and performance of herbivorous beetles
Authors: Orians Colin M. , Huang Cynthia H. , Wild Alexander , Dorfman Katherine A. , Zee Pamela , Dao Minh Tam T. , Fritz Robert S.
Published: October 2003

We examined the preferences and performances of five beetle species (four chrysomelids and one scarab) on two species of willows (Salix sericea and S. eriocephala) and their interspecific hybrids. Beetle species differed markedly in their responses. In preference assays, two chrysomelid beetle species (Calligrapha multipunctata bigsbyana and Plagiodera versicolora) preferred hybrids, two chrysomelids (Chrysomela scripta and Ch. Knabi) preferred hybrids and S. sericea, and the scarab beetle (Popillia japonica) preferred S. eriocephala. Experiments with purified salicortin indicated that salicortin concentration may contribute to these preferences.

The relative performance (growth rate, pupal/adult weight and survivorship) of these beetles on the three willow taxa did not correspond with their feeding preferences. Three species exhibited intermediate performance on hybrid willows (the two Chrysomela spp. and P. japonica); the Chrysomela spp. performed best on S. sericea, while P. japonica performed best on S. eriocephala. One species performed equally well on all three taxa (C. multipunctata bigsbyana). The performance of Pl. versicolora was not tested.

Our results support the general pattern that willow taxa with phenolic glycosides are more acceptable to specialist willow herbivores while those taxa without phenolic glycosides are more acceptable to generalist herbivores. We also show that to predict the relative susceptibility of hybrid and parental plants to herbivores, consideration must be given to the inheritance of traits affecting both preference and performance.
Effect of chronic ingestion of the cysteine proteinase inhibitor, E‐64, on Colorado potato beetle gut proteinases
Authors: Bolter Caroline J. , Latoszek‐Green Marysia
Published: October 2003

Chronic ingestion of the highly active, specific cysteine proteinase inhibitor, E‐64, has a profound effect on Colorado potato beetle (CPB) larval growth, development and survival, as well as on adult fecundity. However, the number of insects surviving to the adult stage did not decrease below 26% with increasing E‐64 concentration above 1.5 μg E‐64 cm−2 leaf surface. The development time to the pupal stage was increased from 13 days, when larvae were reared on control leaves, to 21 days at a concentration of 1.5 μg E‐64 cm−2. The most significant effect of dietary E‐64 was on adult fecundity, with mated females reared on untreated leaves laying an average 62 ± 5.7 eggs daily in the first 10 days, and those maintained on 0.5 μg E‐64 cm−2, laying only 16 ± 2.4 eggs day−1. Females given 1 μg E‐64 cm−2 laid few if any eggs, but started producing egg masses as large as control insects about 5 days after being switched to control leaves. These effects on the insect life cycle were directly related to the degree of inhibition of cysteine proteinase activity in gut extracts. The general proteinase activity in control extracts was 6.5 ± 0.16 units min−1 mg gut−1, which decreased to 1.9 ± 0.16 in guts of insects reared on 1 μg E‐64 cm−2. The proportion of proteinase activity inhibitable by E‐64 decreased from 66% in control guts to 10‐15% in guts from larvae reared on 1 μg E‐64 cm−2. The aspartate proteinase inhibitor, pepstatin, decreased proteinase activity by 35% in control guts. There was no induction of pepstatin‐inhibitable proteinases in response to inhibition by E‐64, and no inhibition of gut enzyme activity by soybean trypsin inhibitor from larvae fed any of the E‐64 concentrations. This study demonstrates that proteinase levels must be significantly reduced to have a pronounced effect on larval growth and survival, while fecundity of mated females is affected by lower concentrations of inhibitor. It also suggests that the CPB may be a difficult pest to control using a more specific, plant‐derived cysteine proteinase inhibitor, such as oryzacystatin.
Adult feeding and lifetime reproductive success in the parasitoid Aphytis melinus
Authors: Heimpel George E. , Rosenheim Jay A. , Kattari David
Published: October 2003

The diet of adult females of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) includes host insects and sugar‐rich foods such as nectar and honeydew. We compared the contributions of host feeding to longevity and fecundity in A. melinus females in the presence and in the absence of honey meals. First, we assessed the longevity of females that were not allowed to oviposit. While the longevity of females fed honey was significantly increased by host feeding (median ages were 30.5 days for host‐fed females and 17 days for females not allowed to host feed), the lifespan of parasitoids not fed honey did not exceed 3 days for any individual and there was no effect of host feeding on longevity in this group. In the second set of experiments, we assessed the fecundity and longevity of females allowed to oviposit. We conducted two experiments, one in which honey was continuously available, and one in which honey was not available. In both experiments, daily observations were made of females that were either allowed to host feed or manually prevented from host feeding. In the presence of honey, host feeding significantly increased both fecundity and longevity, and in the absence of honey, parasitoids died within 2 days and host feeding had no significant effect on either fecundity or longevity. The lifetime fecundity of females fed honey but not hosts exceeded the initial egg complement by 60% on average. Approximately one host per day was used for host feeding whether honey was supplied or not, and each host‐feeding meal contributed approximately 3.9 eggs to the lifetime fecundity of honey‐fed females. In the last experiment, we compared the rate of egg resorption over a 36‐h period in A. melinus females that were deprived of hosts and either fed honey or starved. While no egg resorption was detected in honey‐fed females over this time period, starved females resorbed approximately 9 eggs. Thus, the availability of a sugar‐rich food interacts strongly with host feeding in influencing longevity and fecundity and has a strong direct effect on egg resorption.
Comparison of the performance of Cicadulina leafhoppers on flight mills with that to be expected in free flight
Authors: Riley J. R. , Downham M. C. A. , Cooter R. J.
Published: October 2003

Flight mills are commonly used to assess the relative flight performance of migratory insects, but uncertainties about the rate of energy expenditure on the mill mean that absolute estimates of flight endurance are not usually attempted. In this paper we describe how we measured the power delivered to a lightweight flight mill by tethered Cicadulina storeyi China leafhoppers (Homoptera: Cicadellidae), and compared this to estimates of the power they use to maintain free flight. Our results showed that the leafhoppers were generating more than 0.90 μW of mechanical power when on the mill, and that they probably have 3–4 μW available for free flight. We conclude that whilst flying on the mill, the insects were generating at least 20–30% of the mechanical power needed for free flight, and that this percentage may have been significantly higher.
Location of immature stages of the mushroom insect pest Megaselia halterata in mushroom‐growing medium
Authors: Scheepmaker J. W. A. , Geels F. P. , Smits P. H. , Van Griensven L. J. L. D.
Published: October 2003

Experiments were conducted to examine the location of oviposition by the phorid fly Megaselia halterata (Wood) (Diptera: Phoridae) in uncased and cased compost. Clearly, a majority of the gravid females choose oviposition sites directly after entering the top layer of the compost. In uncased compost, 60% of all adults emerged from the top of four compost layers of equal thickness. When the compost was covered by a casing layer which was still uncolonized by Agaricus bisporus, oviposition was further concentrated in the top compost layer. In this situation, 91% of all adults emerged from the top compost layer whereas only 1.5% emerged from the casing. When the casing layer was colonized by mushroom mycelium, 45% of all adults emerged from the casing layer and 53% emerged from the top compost layer. Further concentration in the top compost layer and the casing layer occurred as a result of upward migration of larvae. When compost was cased after oviposition, up to 43% of all adults emerged from the casing layer. We concluded that in the control of phorid infestations with insect pathogenic nematodes, applications in uncased compost can be restricted to the upper compost layer. When compost and casing are filled simultaneously, nematode applications in the casing layer only could be considered.
Weather‐induced changes in moth activity bias measurement of long‐term population dynamics from light trap samples
Authors: Holyoak M. , Jarosik V. , Novák I.
Published: October 2003

Interpretation of light trap catches of moths is complicated by daily variation in weather that alters flight activity and numbers caught. Light trap efficiency is also modified by wind and fog, and daily weather may effect absolute abundance (numbers actually present). However, actograph experiments and other sampling methods suggest that changes in daily activity are large by comparison to changes in absolute abundance. Daily variation in weather (other than wind and fog) is therefore a form of sampling error in absolute abundance estimates. We investigated the extent of this sampling bias in 26 years of population dynamics from 133 moth species. In a subset of 20 noctuid and geometrid species, daily numbers caught were positively correlated with temperature in 14 species, and negatively correlated with rainfall in 11 species. The strength of correlations varied between species, making it difficult to standardize catches to constant conditions. We overcame this by establishing how weather variation changed with time and duration of the flight period. Species flying later in the summer and for shorter periods experienced more variable temperatures, making sampling error greater for these species. Of the 133 moth species, those with shorter flight periods had greater population variability and more showed significant temporal density dependence. However, these effects were weak, which is encouraging because it suggests that population analyses of light trap data largely reflect factors other than sampling error.
Importance of plant size, distribution of egg masses, and weather conditions on egg parasitism of the European corn borer, Ostrinia nubilalis by Trichogramma ostriniae in sweet corn
Authors: Wang Baode , Ferro David N. , Hosmer David W.
Published: October 2003

Trichogramma ostriniae (Hym: Trichogrammatidae), an egg parasitoid of the European corn borer, Ostrinia nubilalis (Lep: Pyralidae), were released into sweet corn (Zea mays L.) fields to study the effects of weather, plant size and distribution of egg masses on egg parasitism by the wasp. Sentinel European corn borer eggs were stapled onto leaves located in the upper, middle and lower third of sweet corn plants 5 to 35 meters away from the wasp release point in either a radial or grid manner. Weather conditions and plant architecture were monitored during the experiments. Logistic regression was used to analyze the data. The results indicated that percentage of eggs parasitized was negatively related to an increase in leaf area as well as an increase in distance eggs were located from the point of release of wasps. Eggs distributed on plants at different directions from the release point received different levels of parasitism. Eggs that were stapled onto leaves in the upper third of a corn plant received much less parasitism than those on the middle and lower third of the plant. Higher mean temperature adversely affected the level of parasitism during hotter times of the season and conversely, lower temperatures (<17 °C ) reduced the egg parasitism during cooler times of the season. The longer the exposure of eggs to wasps, the higher the level of egg parasitism. However, the levels of egg parasitism for 2 day's exposure were almost the same as that for 3 day's exposure due to the limited longevity and egg‐laying behavior of the wasp. These results suggest that inundative releases of T. ostriniae should be made every two to three days, with multiple release points per hectare. In addition, weather conditions and plant architecture, especially temperature, plant height and leaf area must be taken into consideration to optimize levels of parasitism.
Mortality of eggs, larvae and pupae and larval dispersal of the cabbage moth, Mamestra brassicae, in white cabbage in south‐eastern Norway
Authors: Johansen Nina Svae
Published: October 2003

The mortality of eggs, larvae and pupae and larval dispersal of the cabbage moth, Mamestra brassicae (L.) (Lepidoptera: Noctuidae) was investigated in a series of small‐scale field experiments in white cabbage, Brassicae oleracea var. capitata (L.), and in the laboratory during 1990–1992 in south–eastern Norway. The highest mortality was found in young larvae and in hibernating pupae. In 1990, larval mortality in the first instar was 80% (range 9–97% for the individual cohorts). Most larvae died within the first 1–3 days after hatching. The dispersal activity during these days was high, and failure to establish feeding sites and predation were probably the main mortality causes. Pupal mortality during winter was 90% on average for 1990–1993 (range 81–100%). The main mortality factor was probably unfavourable weather conditions, and indications of cold stress were found. The impact from parasitoids and diseases was generally low. Trichogramma semblidis (Aurivillius) (Trichogrammatidae) was reared from M. brassicae eggs in very low numbers in 1991. Larval parasitism increased from < 1% in 1990 to almost 24% in 1992, and was almost totally caused by the braconids Microplitis mediator (Haliday) and Aleiodes (Aleiodes) sp. Predation of frozen larvae on the soil surface was 75% on average (range 63–96%) during 1990–1992 in first instar larvae and decreased gradually with larval age. The consumption rates of Philonthus atratus (Gravenhorst) (Staphylinidae) and the carabids Bembidion tetracolum (Say), Pterostichus melanarius (Illiger) and Harpalus rufipes (Degeer) on M. brassicae eggs and larvae were investigated in non‐choice experiments in the laboratory. A preliminary survival model based on estimates of the mortality factors identified in this study is presented.
Peripheral‐zone treatments for plum curculio management: validation in commercial apple orchards
Authors: Vincent C. , Chouinard G. , Bostanian N. J. , Morin Y.
Published: October 2003

Peripheral applications of organophosphate insecticides were evaluated as an alternative strategy for controlling adult plum curculio, Conotrachelus nenuphar Herbst (Coleoptera: Curculionidae) in four commercial orchards in Quebec, Canada. Each orchard was partitioned into a reference and an experimental plot to compare the classical full plot treatment with a peripheral treatment alternative. The experimental plots were divided into five zones, i.e. central, North, South, West and East. Peripheral zones were defined as the first five rows of apple trees (or 20 m wide). Plum curculio adults were monitored weekly by limb tapping. Fresh oviposition scars were evaluated by examining 20 fruitlets per tree on each outermost tree in the peripheral zone and 20 fruit on 25 trees in the central zone. Azinphosmethyl treatments were carried out in the zones where more than 1% fruitlets bore fresh ovipositional scars. Fruit damage was mostly (92%) found in the peripheral zones. Plum curculio damage at harvest varied from 0.0 to 0.7% and from 0.0 to 0.8% in the experimental and reference plots respectively. Total insect damage on fruit at harvest varied from 1.3 to 3.8% in the experimental plots, and from 0.4 to 5.0% in the reference plots. In 1991, there were no significant differences between population indices of the spotted tentiform leafminer, the apple aphid, leafroller species and cicadellids in the peripheral versus central zones. In the experimental plots, populations of woolly apple aphid, two‐spotted spider mite and apple rust mite were significantly higher in peripheral zones than in the central zones. In 1992, there were no significant differences between population indices of peripheral versus central zones for both experimental and reference plots. All localities and years pooled, peripheral zones of experimental plots received 1.22 insecticide treatments, against 1.29 for reference plots. However, central zones of experimental plots received 0.38 insecticide treatments, against 1.13 for reference plots. Assuming a 20 m peripheral zone and a 10 ha square orchard, the percent reduction in insecticides would be ca. 75%.
Effects of linear furanocoumarins on the herbivore Spodoptera exigua and the parasitoid Archytas marmoratus: host quality and parasitoid success
Authors: Reitz Stuart R. , Trumble John T.
Published: October 2003

We assessed the effects of three photoactivated linear furanocoumarins, secondary plant metabolites present in Apium spp. (Apiaceae) and other taxa, on the larval‐pupal parasitoid, Archytas marmoratus (Townsend) (Diptera: Tachinidae) and the host Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), in the presence and absence of ultraviolet radiation. These results then were compared with previously described responses of Archytas marmoratus and other hosts to different plant allelochemicals. Ultraviolet radiation had no consistent detrimental effects. Increasing concentrations of linear furanocoumarins (from 0 to 0.029% of fresh weight) increased mortality of both the host and parasitoid. Increasing linear furanocoumarin levels also prolonged larval development of surviving S. exigua, but had no effect on pupal developmental time or pupal mass. Consequently, there was no effect of increasing linear furanocoumarin levels on surviving parasitoid development time (from the time of host pupation) or size. These results indicate the effects of linear furanocoumarins are mediated through effects on the host. Because reported responses of Ar. marmoratus to other allelochemicals (e.g., flavones, methyl ketones) are mediated through host effects, these results support the hypothesis that Ar. marmoratus displays a generalized response to plant allelochemicals that are predictable based on host mediated effects.
Spatial distribution of bibionid larvae in agricultural grassland
Authors: Blackshaw R.P. , D'Arcy‐Burt S.
Published: October 2003

The distribution of bibionid larvae in agricultural grassland was investigated. They tend to occur sporadically and at low population density. More detailed sampling within a field showed that numbers were highest adjacent to a hedgerow with most being found 6–11 m from the hedge. Log variance/log mean relationships were established for counts of Bibio johannis and Dilophus febrilis larvae collected from soil cores in grassland. Both species were highly aggregated. An area of grassland (160 cm × 80 cm) was divided into 128 soil blocks and B. johannis larvae extracted. Almost all larvae were associated with aggregations. The two‐phase mozaic method of Pielou (1974) was applied to larval counts from different sized concentrically collected soil cores. Larval patches were not randomly distributed. Time‐lapse video studies of bibionid larvae were made and showed both aggregation and processional behaviour. This was associated with chemical stimulation which is probably used to maintain larval groupings in the field. There was evidence for two levels of aggregation. The first is due to groups of larvae arising from eggs laid by a single female and the second, larger scale, aggregation is due to factors that influence the distribution of adult flies.
Effect of entomopoxvirus infection of the smaller tea tortrix, Adoxophyes sp. on the development of the endoparasitoid, Ascogaster reticulatus
Authors: Nakai Madoka , Sakai Takuro , Kunimi Yasuhisa
Published: October 2003

Infection of Adoxophyes sp. (Lepidoptera: Tortricidae) larvae by an entomopoxvirus (AsEPV) adversely affected the development of the endoparasitoid, Ascogaster reticulatus Watanabe (Hymenoptera: Braconidae). Parasitoid larvae developing in AsEPV‐infected hosts grew more slowly and spent more time in their hosts than did parasitoid larvae developing in noninfected hosts. Percentages of emergence of larval parasitoids that developed in AsEPV‐infected hosts were significantly lower than those of parasitoids that developed in noninfected hosts. Parasitoid larvae in AsEPV‐infected host perished when their hosts died of AsEPV infection. Significant numbers of parasitized and infected larvae exhibited apolysis to the final instar, whereas noninfected‐parasitized larvae died in the penultimate instars due to emergence of parasitoids.
Density‐related sterility in Eretmocerus mundus
Authors: Gerling Dan , Fried Rivka
Published: October 2003

While studying the reproductive capacity of Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) we found that varying numbers of females were sterile. Investigations showed that sterility occurred also in field populations, but at a very low rate. Laboratory sterility was significantly correlated with crowding of the parental females during oviposition. Whitefly hosts from which fertile of sterile females emerged did not differ in size, neither did the hind tibiae of fertile females differ in dimensions from those of sterile ones. Behavior of sterile females differed from that of the fertile ones in several parameters. They exhibited less leg drumming, used the ovipositor more frequently and for shorter durations, and changed more readily from probing to host stinging, and from a number of activities to walking. Altogether, their behavior appeared more restless and caused them to contact more hosts than fertile females. The possibility that the sterility is caused by crowding alone, or by the activity of microorganisms acting under crowded conditions, and the merits of the phenomenon for biological pest control are discussed.
Effect of host diet on acceptance of eastern spruce budworm eggs by Trichogramma minutum
Authors: Song S. J. , Bourchier R. S. , Smith S. M.
Published: October 2003

The acceptance behaviour of the parasitic wasp, Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae), was studied on two types of egg masses of eastern spruce budworm (SBW), Choristoneura fumiferana Clemens. Host eggs were obtained from moths that had been fed balsam fir or artificial diet during their larval stages. Parasitoids were reared from both types of hosts. Host acceptance assays were conducted where females were provided with a single egg mass and with a choice between egg masses. Regardless of the parasitoid's rearing host, females parasitised hosts reared from artificial diet more often than those from balsam fir. Response was consistent in both no‐choice and choice assays. Rejection of hosts tended to occur during the examining stage of behaviour, suggesting that acceptability is judged externally. If a host was accepted, the same number of eggs were laid per egg mass regardless of treatment.
Allozyme variation among Brazilian and U.S. populations of Rhyzopertha dominica resistant to insecticides
Authors: Guedes Raul Narciso C. , Kambhampati Srinivas , Dover Barry A.
Published: October 2003

The lesser grain borer (Rhyzopertha dominica (F.)) is an important pest of stored grain in many parts of the world (Paleartic, Ethiopian, Oriental, Australian, Neotropical, and Neartic regions) with the ability to fly long distances. These insects have been shown to be resistant to organophosphorus insecticides in several studies. Polyacrylamide gel electrophoresis was used to assess the genetic variability within and among eight Brazilian and seven United States populations of R. dominica and to determine how insecticide resistance may be spreading within both countries. Significant variation in allele frequency among populations was observed at all six polymorphic enzyme loci that were examined. The Brazilian and U.S. populations were genetically differentiated from one another; populations within the U.S. and those within Brazil were also differentiated from one another. The mean genetic similarity among the seven U.S. populations collected in a small region in northeast Kansas was smaller than that among eight Brazilian populations collected in a relatively large geographical area. These results are consistent with the resistance ratios to chlorpyriphos‐methyl in R. dominica populations from Brazil and the U.S. and the information available concerning patterns of flight activity in this insect.
Field‐scale effects of farming practices on linyphiid spider populations in grass and cereals
Authors: Thomas C.F.G. , Jepson P.C.
Published: October 2003

Linyphiid spiders were sampled in three grass and four cereal fields, between October 1989–October 1990, and from one grass and one cereal field, from June–August 1991. Population growth and decline were characteristic of field type and pattern of management. Agricultural operations caused large population depletions: insecticide applications, cutting grass for silage and autumn cultivations reduced spider populations by 56% to 96%; heavy grazing caused virtual extinction. Aerial dispersal activity, monitored by water traps, showed high dispersal frequency with highest intensity in June, July and August. The results are discussed with reference to the large‐scale spatial structure of linyphiid spider populations and the use of spatially dynamic models to predict metapopulation size as a function of patterns of crop management, land‐use and landscape structure.
Prediction of flight of apple sawfly, Hoplocampa testudinea, using temperature sums
Authors: Zijp J. P. , Blommers L. H. M.
Published: October 2003

A method to predict the beginning of the flight of apple sawfly, Hoplocampa testudinea (Klug) (Hymenoptera, Tenthredinidae) is presented. Adults were monitored during 8 years at the experimental orchard ‘De Schuilenburg’, Kesteren, The Netherlands, with visual sticky traps. Temperature sums, accumulated until the day of the first capture of sawfly, were calculated for different starting dates of the summations. Beginning on 1 January, variation of the temperature sums, calculated in each of 8 years, decreased when later starting dates for temperature summation were chosen, reaching a minimum on 1 April for soil temperatures (−5 cm). The soil temperature sum, accumulated from 1 April until the first capture, was on average 134 day‐degrees above a threshold of 4 °C. So this was the most suitable starting date to predict the beginning of sawfly flight activity. As use of the summation method based on air temperatures is in practice more appropriate for timing of trap installation by extension services and apple growers, trap deployment is recommended at an adapted value of 157 day‐degrees from 15 March.
The effects of parasitism by an encyrtid parasitoid, Anagyrus pseudococci on the survival, reproduction and physiological changes of the mealybug, Planococcus citri
Authors: Islam K. S. , Perera H. A. S. , Copland M. J. W.
Published: October 2003

Survival, reproduction and some biochemical changes in the citrus mealybug, Planococcus citri (Risso) parasitized by the endoparasitoid, Anagyrus pseudococci (Girault) are reported. The parasitized younger mealybugs were more likely to die than be successfully parasitized. The mean duration (±SE) required for mortality other than mummification were 1.85 ± 0.06, 2.48 ± 0.14 and 2.89 ± 0.17 days for first, second and third instar P. citri respectively. Hosts parasitized in the first instar did not produce any mummies while the second and third instar nymphs and adult stages of the mealybugs were mummified on average 8 to 11 days after attack. Parasitization caused cessation of normal fecundity as well as induction of early egg maturation of the mealybugs. The mealybugs parasitized in the adult stage produced a few eggs but the fecundity of unparasitized mealybugs was about 40 fold higher than that of parasitized mature adults. Parasitized pre‐ovipositing and mature adults laid eggs within 24 h of attack. SDS‐PAGE analysis of the body content of the parasitized mealybugs after 24 h and 48 h of parasitization and before egg hatch revealed an increase in the concentration of some proteins. Response to wound reactions was not visible either as formation of extra protein bands or increased density of the existing bands. The possible effect of parasitism on the changes of the reproductive physiology of the host is discussed.
The influence of temperature on the life table of Hyperaspis notata
Authors: Dreyer B. Stäubli , Neuenschwander P. , Bouyjou B. , Baumgärtner J. , Dorn S.
Published: October 2003

The coccinellid Hyperaspis notata Mulsant was introduced into Africa for the biological control of the cassava mealybug, Phenacoccus manihoti Matile‐Ferrero. Two cohorts of strains, one originating from Southern Brazil and Paraguay feeding on P. manihoti, and one from Colombia feeding on Phenacoccus herreni Cox & Williams were studied at different temperatures between 15 and 34 °C and age‐specific life tables were constructed. Although in the areas of origin the climatical conditions and the food sources are different, the survivorship and developmental times at the same temperature differed little among the two strains, the Colombian strain being slightly more tolerant to high temperatures. Jacknife estimates of the intrinsic rates of increase (rm) peaked very close to 30 °C for the two strains.
Venturia canescens parasitizing Galleria mellonella and Anagasta kuehniella: differing suitability of two hosts with highly variable growth potential
Authors: Harvey Jeffrey A. , Vet Louise E.M.
Published: October 2003

Venturia canescens (Grav.) (Hymenoptera: Ichneumonidae) is a solitary larval koinobiont endoparasitoid, ovipositing in several larval instars of different pyralid moth species that are pests of stored food products. After oviposition, the host larva continues to feed and grow for at least several days, the precise time doing so depending on the stage attacked. We examined the relationship between host stage and body mass on parasitoid development in late second to fifth instars of two hosts with highly variable growth potential: the wax moth, Galleria mellonella (L) and the flour moth, Anagasta kuehniella (Zeller)(Lepidoptera: Pyralidae). G. mellonella is the largest known host of V. canescens, with healthy larvae occasionally exceeding 400mg at pupation, whereas those of A. kuehniella rarely exceed 40 mg at the same stage. Parasitoid survival was generally higher in early instars of G. mellonella than in later instars. By contrast, percentage adult emergence in A. kuehniella was highest in late fifth instar and lowest in late second instar. A. kuehniella was the more suitable host species, with over 45% adult emergence in all instars, whereas in G. mellonella we found less than 35% adult emergence in all instars. Adult parasitoid size increased and egg‐to‐adult development time decreased in a host size‐ and instar‐specific manner from A. kuehniella. The relationship between host size and stage and these fitness correlates was less clear in G. mellonella. Although both host species were parasitized over a similar range of fresh weights, the suitability weight‐range of A. kuehniella was considerably wider than G. mellonella for the successful development of V. canescens. However, in hosts of similar weight under 5 mg when parasitized, larger wasps emerged from G. mellonella than from A. kuehniella. Parasitoid growth and development is clearly affected by host species, and we argue that patterns of host utilization and resource acquisition by parasitoids have evolved in accordance with host growth potential and the nutritional requirements of the parasitoid.
The relation between dispersal and survival of Lobesia botrana larvae and their density in vine inflorescences
Authors: Torres‐Vila Luis M. , Stockel Jacques , Roehrich Roger , Rodríguez‐Molina M. Carmen
Published: October 2003

Dispersal and survival of Lobesia botrana Den. & Schiff. (Lepidoptera: Tortricidae) larvae in a simulated first generation and the relationship with their density on vine inflorescences were studied under field conditions. Artificial infestations with neonate larvae were conducted at densities of 5, 10, 15, 20 and 25 individuals per vine inflorescence. Larvae had a considerable dispersal capacity on the vine espalier and were able to reach several inflorescences around those artificially infested. Dispersal downwards (63.1%) was significantly more frequent than upwards (36.9%), probably because larvae move down the vine plant using silk threads. However, the fact that there was upwards dispersal provides evidence that larvae are capable of active locomotion upwards on the vine plant structure. Mean distances covered by larvae ranged between 10 and 30 cm, with a maximum as far as 45 cm. The longest displacements were not associated with the downward dispersal. The maximum distance covered by larvae was positively correlated with larval density. Mean distance and larval density were not correlated, but mean distances covered at high larval densities were significantly higher than at low densities. At higher larval densities, the proportion of larvae which established in the artificially infested inflorescences decreased whereas the proportion of dispersing individuals increased. However, as a result of the balance between establishment and dispersal, larval survival did not differ significantly among larval densities (26–44%). The results obtained suggest that larval dispersal must be taken into account when preimaginal stages are sampled to determine whether damage thresholds are reached in an integrated pest management program.
Fitness consequences of ovicide in a parasitoid wasp
Authors: Mayhew Peter J.
Published: October 2003

Ovicide, superparasitism and host rejection are alternative reproductive tactics facing female parasitoid wasps encountering an already‐parasitized host. Superparasitism is simply the addition of an egg or a clutch of eggs by the secondary parasitoid, but under ovicide the primary clutch is removed or destroyed. Host rejection occurs if the wasp leaves without laying a clutch.

The ectoparasitoid Laelius pedatus (Say) (Hymenoptera: Bethylidae) performs ovicide in this situation. Clutch manipulation experiments show that secondary clutches suffer high mortality in competition with primary clutches, which increases with increasing time delay between clutches. Primary clutches however suffer little in competition with secondary clutches, even if there is minimal time delay between clutches. These data suggest that the offspring of ovicidal females are substantially fitter than the offspring of superparasitizing females.

Handling time and clutch size do not differ significantly between first (sole) parasitoids and second (ovicidal) parasitoids. The same is true for offspring survival and development time. However, offspring of second females are slightly smaller. This suggests that parasitized and unparasitized hosts are resources of similar quality when ovicide is performed.

These data strongly support the predictions of evolutionary models of ovicide. They may also give some insight into the taxonomic distribution of ovicide in parasitoids.
Semiochemistry of aposematic seed bugs
Authors: Aldrich J. R. , Leal W. S. , Nishida R. , Khrimian A. P. , Lee C.‐J. , Sakuratani Y.
Published: October 2003

(E)‐2,7‐Octadienyl acetate and (E)‐2‐octenyl acetate (1:10 by volume) were identified as a pheromone attractive to both sexes of the lygaeid bug, Tropidothorax cruciger. In a parallel investigation of Neacoryphus bicrucis (Lygaeidae), (E,E)‐2,4‐hexadienyl acetate and phenethyl acetate (≈9:1) were identified from males, and found attractive to both sexes of adults in the field plus a tachinid fly parasitoid of the bugs. In N. bicrucis, the pheromone was clearly shown to come from the tubular accessory glands of the metathoracic scent gland; this evidence, plus earlier literature reports for other species, indicate that male lygaeids are the pheromone emitters. In another lygaeid, Oncopeltus fasciatus, 2‐isobutyl‐3‐methoxypyrazine was identified in the cardiac glycoside‐laden fluid sequestered from milkweed hosts and expelled by these bugs when they are attacked. Alkyl methoxypyrazines are warning odorants associated with poisonous insect secretions, and their presence in O. fasciatus indicates that the plant‐derived chemical defense of lygaeines is more elaborate than previously appreciated.
Resistance to the pink potato aphid, Macrosiphum euphorbiae, in two accessions of Lycopersicon hirsutum f. glabratum
Authors: Musetti Luciana , Neal Jonathan J.
Published: October 2003

Accessions PI 126449 and PI 134417 of wild tomato, Lycopersicon hirsutum f. glabratum C.H. Mull, were assessed for resistance to the pink potato aphid, Macrosiphum euphorbiae (Thomas). Aphid populations under field and greenhouse conditions were significantly lower on the L. hirsutum f. glabratum plants compared to L. esculentum. Removal of trichome glands and exudates by wiping the leaf surface resulted in a dramatic decrease in aphid mortality. Compared to L. esculentum, aphid behavior on the L. hirsutum f. glabratum plants was characterized by 40 to 52% abandonment, delay in time for first probe, reduction of number and duration of probes and decrease in the total proportion of time probing. Removal of the trichomes reduced the percentage of abandonment and increased the total proportion of time probing. Density and type of glandular trichomes varied among plant lines and on adaxial and abaxial leaf surfaces within a line, particularly for the L. hirsutum f. glabratum plants. PI 134417 was, in general, more resistant to the aphids than PI 126449.
Test for predation effects of single versus multiple species of generalist predators: spiders and their insect prey
Authors: Riechert S.E. , Lawrence K.
Published: October 2003

The prediction that single spider species (as exemplary generalist predators) limit associated prey populations to the same extent that species assemblages do was tested in a well controlled and replicated old field experiment involving the following treatments: (1) the natural spider assemblage (2) a numerically prominent web building spider, (3) a numerically prominent wandering spider, (4) a biomass prominent web‐builder, and (5) a biomass prominent wandering spider. Pest insect numbers were significantly higher in spider removal controls than in any spider treament over the four month period of the study, both in terms of total numbers and per spider effects. The individual spider species, in general, showed reduced prey limitation effects relative to that of the spider assemblage, though the magnitudes of these differences were small when compared to those exhibited between the various treatments and the spider removal control. When insect numbers were partitioned according to taxa, no treatment was found to have limited the predaceous insects nor the phytophagous hemipterans. All treatments, however, showed significant limiting effects on the phytophagous homopterans, coleopterans, and dipterans in the old field system, and other taxa were significantly reduced in at least one treatment in addition to the spider assemblage as a whole.