Pupation by Viburnum leaf beetle (coleoptera: chrysomelidae): behavioral description and impact of environmental variables and entomopathogenic nematodes

Pyrrhalta viburni (Paykull), a new landscape pest in the United States, feeds in both the larval and adult stages on foliage of plants in the genus Viburnum. The insect is univoltine, with larvae active in spring and adults throughout the summer months. Experiments were conducted to determine the depth of pupation in the soil; the impact of substrate texture, moisture content, and temperature on pupation success; and ability of entomopathogenic nematodes to kill larvae when they enter the substrate to pupate. Larvae burrowed only a short distance into the substrate when pupating; 97-100% were found within the top 3 cm of a column of soil or sand and soil mixture in the laboratory. Larval mortality before pupation was low at 22 degrees C but considerably higher at 30 degrees C; at both temperatures, pupation success was lowest on a mixed substrate and higher (and equivalent) on sand or soil alone. Survivorship to adult was influenced by both temperature and substrate moisture content; at 22 degrees C, 56% percent of pupating larvae emerged as adults at 75% moisture content compared with only 25 at 25% moisture content. Emergence of adults was negligible at 30 degrees C, regardless of moisture content. Heterorhabditis bacteriophora and Steinernema carpocapsae were very effective biocontrol agents in laboratory bioassays, reducing adult emergence by 76-100%, with nematode applications made before pupation being more effective than those made after pupation, and H. bacteriophora consistently (but not significantly) more effective than S. carpocapsae. Management methods that take advantage of pupation behaviors are discussed.     

Regulation ofHelicoverpa zea larval behavior by the parasitoidEucelatoria bryani

The parasitoidEucelatoria bryani Sabrosky regulates the larval behavior of its hostHelicoverpa zea (Boddie). Parasitized third, fourth and fifth instars burrow into the soil 0.7–3.4 days earlier than unparasitized larvae that normally enter the soil to pupate at the end of the fifth and final larval instar. Parasitized third instars molt once then burrow as fourth instars, one instar earlier than normal. WhenE. bryani pupariated on the soil surface in the field, none survived to the adult stage. However,E. bryani adults emerged from 49.2% of hosts that had burrowed into the soil. By accelerating the timing ofH. zea burrowing behavior and causing host larvae to enter the soil before death,E. bryani ensures its pupariation in an environment with improved protection against natural enemies and lethal temperatures.     

The effects of temperature on development of the large narcissus fly (Merodon equestris)

Eggs, larvae, pupae and adults of the large narcissus fly (Merodon equestris) were reared at a series of constant temperatures between 9–24°C. Egg development required from 37 days at 9°C to 7 days at 21.5°C. The low-temperature threshold for development was 6.7°C. Larvae reared at 1424°C were fully-grown after 18 weeks, but it took much longer for such insects to pupate, and adult flies emerged only after about 45 weeks of development. Large narcissus flies enter diapause during the larval stage and overwinter as fully-fed larvae, forming pupae in the following spring. Post-winter pupation and pupal development took from 169 days at 10°C to 36 days at 21.5°C. Of this, pupal development required from 91 days at 10°C to 19 days at 21.5°C. The low-temperature threshold for post-winter pupation and pupal development was 7.1°C, and for pupal development alone, 7.2°C. Females maintained at or below 19°C laid few eggs, whereas some females kept at or above 21.5°C laid more than 100 eggs (mean 69 ± 36). Approximately 50% of females maintained at or above 21.5°C laid less than 10 eggs during their lifetime. The mean egg-laying time was 6 to 9 days. Although temperatures at or below 19°C inhibited mating, once a female had mated, such temperatures did not prevent oviposition.     

Genetics and ecology of Drosophila melanogaster larval foraging and pupation behaviour

In this paper we show that, (1) Drosophila melanogaster larvae utilize a variety of pupal microhabitats in an orchard, (2) variation in larval foraging path length, pupation distance from the food and pupal microhabitat preference (on or off the fruit) is genetically based and, (3) variation in these behaviours can be maintained in a spatially heterogenous environment since there is a reversal in pupation site suitability in wet and dry pupal microhabitats. Differences in path length in both laboratory and natural populations can be attributed to genes on the second pair of chromosomes and is under simple genetic control, whereas differences in pupal height are polygenically inherited (the second pair of chromosomes influences pupal height three times more than the third pair). Pupae collected from on-fruit sites had shorter foraging path lengths and lower pupal heights than off-fruit populations. Populations from the orchard maintained their field pupal microhabitat preferences even after 1 year of rearing them in the laboratory. Larvae with the sitter larval phenotype (short path lengths and low pupal heights tended to pupate more on-fruit than those with the rover phenotype (long path lengths and high pupal heights). To determined if these genetically based differences in microhabitat preference contributed to fitness, larval pupation behaviour was studied in a “field assay” (dish with fruit on soil) with soil water content varied. At low soil water contents, pupal survivorship was significantly better on the fruit whereas, at high soil water contents, survivorship was better in the soil. There was a reversal in which microhabitat (dry or wet) was a better site for pupation. In the field environment where soil water content fluctuates in space and time, such a reversal would explain the maintenance of genetic variation for these larval behaviours. Another selective agent acting on D. melanogaster larvae in our orchard is parasitization by Asobara tabida. This parasitoid parasitizes larvae with high locomotory scores (e.g. rovers) significantly more than those with low scores (sitters). This study relates laboratory phenotypes to field phenotypes thereby linking the ecological, behavioural and genetic components of larval habitat selection in D. melanogaster.     

Toxicity of acephate to larvae of gypsy moth as a function of host plant and bioassay method

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.     

Age-dependent physiological responses of last instarHelicoverpa zea larvae to oral and topical application of precocene II

Newly-ecdysed last instar larvae ofH. zea grouped into 100-, 200-, 300-, or 400-mg categories were fed diet containing precocene II or given precocene II topically on the abdomen. The time for larvae to reach a maximal weight, time to pupation, growth rate, and the amount of precocene II excreted were calculated. Younger larvae of lower weights, which were fed or topically treated with precocene II required more time to reach their maximal weight, had a lower maximal weight, a lower growth rate, and required more time to pupate than control larvae. Older larvae represented by the largest weight category were less sensitive to precocene II, had a shorter delay in reaching maximal weight, and a shorter delay in the time to pupation than control larvae; larvae in the largest weight category that were fed precocene II also had smaller decreases in the growth rate. Growth rate declines for larvae given topical doses of precocene II, however, were largest for the oldest larvae. All larvae given a single topical dose excreted precocene II for several days and were most efficient at eliminating smaller doses; larger, older larvae excreted more precocene II than smaller, younger larvae. Age-dependent responses to precocene II indicate that growth and metabolic processes, as well as xenobiotic metabolism, change in last instar larvae.     

Food‐availability dependent premature metamorphosis in the bean blister beetle Epicauta gorhami (Coleoptera: Meloidae), a hypermetamorphic insect that feeds on grasshopper eggs in the larval stage

Larvae of the bean blister beetle, Epicauta gorhami, feed on only grasshopper eggs and undergo hypermetamorphosis with pseudopupal diapause in the fifth instar. Whether E. gorhami larvae enter pseudopupal diapause or pupate directly from the fourth instar is controlled by temperature and photoperiod. In nature, larvae are confronted with a significant variation in the availability of food, suggesting the possibility that feeding conditions may also affect the diapause incidence. Here, we addressed this issue by changing the feeding conditions in the fourth instar under conditions of 16 h light : 8 h dark (LD 16 : 8) at 25°C. Food deprivation reduced the length of instar and increased the tendency to pupate, leading to the early eclosion of a small adult. Even non‐feeding fourth‐instar larvae pupated. Regardless of the timing of food deprivation, the post‐feeding larval period was constant and equivalent to that of ad libitum‐fed larvae, suggesting that premature exhaustion of the food supply triggers the initiation of pupation. In agreement with these results, when larvae were fed on intact grasshopper egg pods of various sizes from four species, those that fed on smaller egg pods had a decreased tendency to pseudopupate (i.e., to enter diapause). Food‐deprived larvae showed a clearer photoperiodic response and had a shorter critical day‐length. Thus, in E. gorhami, feeding conditions do not affect pupation success, but do affect the tendency to pupate or pseudopupate. This is the first report of the occurrence of premature pupation in carnivorous insects. We discuss our findings in the context of the natural history and behavioral ecology of E. gorhami.     

Prepupal Building Behavior in Drosophila melanogaster and Its Evolution under Resource and Time Constraints

Structures built by animals are a widespread and ecologically important ‘extended phenotype’. While its taxonomic diversity has been well described, factors affecting short-term evolution of building behavior within a species have received little experimental attention. Here we describe how, given the opportunity, wandering Drosophila melanogaster larvae often build long tunnels in agar substrates and embed their pupae within them. These embedded larvae are characterized by a longer egg-to-pupariation developmental time than larvae that pupate on the surface. Assuming that such building behaviors are likely to be energetically costly and/or time consuming, we hypothesized that they should evolve to be less pronounced under resource or time limitation. In accord with this prediction, larvae from populations evolved for 160 generations under a regime that combines larval malnutrition with limited developmental time dug shorter tunnels than larvae from control unselected populations. However, the proportion of larvae that embedded before pupation did not differ between the malnutrition-adapted and control populations, suggesting that tunnel length and likelihood of embedding before pupation are controlled by different genetic loci. The behaviors exhibited by wandering larvae of Drosophila melanogaster prior to pupation offer a model system to study evolution of animal building behaviors because the tunneling and embedding phenotypes are simple, facultative and highly variable.     

Control of diapause in codling moth larvae

Diapause in a New Zealand strain of codling moth (Cydia pomonella Linnaeus [Lepidoptera: Olethreutidae]) was induced in larvae by photoperiods of 15 h or less. Once diapause had been initiated, it could not be terminated by any combination of conditions tested for at least 20 days after cocooning. In diapausing larvae a low rate of pupation occurred at 25 °C under a long day (18 h) photoperiod. A high rate of pupation was achieved under a long day regime when larvae were decocooned, and provided with apple as nourishment. Diapause could be terminated predictably in 94–100% of larvae by 1) conditioning at 15 °C and constant darkness for periods of 40–100 days, then 2) chilling at 2±2 °C and constant darkness for 20–50 days followed by 3) any post-chill condition periods at 25 °C, 18 h photoperiod. Complete diapause termination was achieved when 100 days conditioning was followed by 30 days or 50 days post-chill period. Under these conditions, 76% termination occurred in the post-chill period after 10 days, and 93% after 25 days.To terminate diapause in codling moth larvae, we recommend that a 100 days conditioning followed by 30 days chilling and 50 days post chilling periods be used.     

Analysis of brood development in the ant Amblyopone silvestrii, with special reference to colony bionomics

There are five larval instars in the temperate, subterranean ponerine ant, Amblyopone silvestrii (Wheeler). An examination of the seasonal developmental patterns of immatures collected from more than 100 colonies collected in the field revealed that most or all of the newly hatched individuals overwintered as second to fifth instar larvae and emerged as adults in the next summer. The fifth instar larvae were most abundant in the colony's larval population all year round. The number of eggs present in the nest diminished temporarily in midsummer, although queens collected during this period maintained fully developed ovaries with mature oocytes. When the larvae matured, they were usually moved to temporary nests away from the nest area of the colony and finished pupation and eclosion there, while accompanied by a small number of workers. Pupation of sexuals occurred in the more distant cocoon chambers compared with pupation of workers.     

Temperature-related fluctuations in the timing of emergence and pupation of Windermere alder-flies over 30 years

1. From 1966 to 1995, dates were recorded when adult alder-flies, Sialis lutaria L., were first seen (30-year range: 23 April – 25 May), 50% of the maximum density occurred (4 May – 4 June), and maximum density occurred (11 May – 17 June) along 200 m of Windermere shore. These emergence dates occurred at similar temperatures, estimated by mean values for both the emergence date and the week prior to emergence. The latter was the least variable at 10.1 °C (95% CL ± 0.37) for start of emergence, 11.2 °C (± 0.49) for 50% maximum density, 14.2 °C (± 0.51) for maximum density.
2. Final-instar larvae pupated in damp soil just above the water line. As laboratory temperatures were increased slowly from an initial 5 °C, the cumulative number of larvae leaving the water to pupate increased. A quadratic equation described this relationship from a threshold temperature of 7.2 °C to completion at 14.0 °C (50% point, 9.3 °C). The relationship between successful pupations and constant temperatures in the laboratory was well described by a quadratic equation with an optimum 14.9 °C (over 90% success) and no success outside the range 7–23 °C. A negative power-function described the relationship between days required for pupation and temperature, ranging from c . 28 days at 8.2 °C to c . 4 days at 22.1 °C.
3. Dates for larvae leaving the lake to pupate were back-calculated from dates for adult emergence, using the power-function for pupation time. Mean temperatures for estimated dates on which larvae left the lake to pupate were less variable than those for adult emergence, being 7.5 °C (± 0.20) for the start of pupation, 9.4 °C (± 0.16) for 50% maximum density, 13.7 °C (± 0.16) for maximum density. These values are similar to those obtained in the laboratory and can be used to predict pupation and adult emergence for different temperature regimes.     

Coelomomyces opifexi Pillai & smith (Coelomomycetaceae: Blastocladiales) V. Development of the fungus in pupae and adults of Aedes australis

Abstract

Late-instar Aedes australis larvae were experimentally infected with Coelomomyces opifexi, and the subsequent development of the fungal parasite was studied. Five separate experiments involving 1190 infected larvae were conducted. Of these larvae, 114 continued development and pupated; 38 of them contained sporangia. Histological studies indicated that parasite development slowed down, if not ceased, following pupation of infected larvae, and the presence of sporangia in adults reflected the degree of advancement of infection in the larvae at pupation.     

南美斑潜蝇蛹期的生物学特性

南美斑潜蝇Liriomyzahuidobrensis在 1 5 ,2 0 ,2 5 ,30 ,35℃时 ,其蛹的历期分别为 34 5 ,1 5 8,1 0 1 ,7 2d ,而在 35℃时则不能正常羽化。土壤相对含水量为 30 %～ 90 %均比较适合南美斑潜蝇蛹的发育 ,就死亡率而言 ,它们之间没有显著差异。浸水处理表明 ,南美斑潜蝇的预蛹及蛹的初期和末期对浸水比较敏感 ,死亡率均达到 90 %以上 ,而处于中间期的蛹对浸水相对不敏感。田间调查和室内饲养均发现 ,南美斑潜蝇在 1 2时以前的化蛹个数占 1d总化蛹个数的 90 %以上 ,而 1 4时以前的羽化数占 1d总羽化数的 99%以上。南美斑潜蝇化蛹的场所在不同时期不同的蔬菜上有所不同 ,越冬时主要是以蛹在越冬寄主田的土壤中越冬 ,在生长季节 ,除了在菜豆的叶片反面化蛹外 ,其它蔬菜上则是在土壤和下部叶鞘上化蛹。     

Density-dependent natural selection does not increase efficiency

Summary Populations ofDrosophila melanogaster kept at high population density (K-selected) for 125 generations have higher larval viability than populations kept at low densities (r-selected) when both are raised under crowded conditions. In additionK-selected adults that emerge from crowded cultures are larger than theirr-selected counterparts. These differences cannot be explained by differences in efficiency of food use. The minimum food required for successful pupation is actually greater in theK-selected populations. I conjecture that there may be a trade-off between minimum food requirements and competitive ability, which has changed substantially in theK-selected populations. The possibility thatK-selected larvae can dig more more deeply and gain access to unused food is examined and rejected as a possible explanation of the viability differences. Evidence is provided supporting the hypothesis that the differences in viability may be due to an increased tendency of theK-selected larvae to pupate off the surface of the medium.     

Male mate-locating behavior inEuphydryas chalcedona (Lepidoptera: Nymphalidae) related to pupation site preferences

Males of the checkerspot butterfly (Euphydryas chalcedona)patrol and perch near but not on the larval foodplant in search of females. Experiments with tethered butterflies show that searching males chase virgin females for longer times than they do mated females or males. The larvae leave the larval food-plant to pupate. The correspondence between the distance from the larval foodplant to pupation sites and where males search for females suggests that male mate-locating behavior has evolved to maximize the rate of encounters with newly emerged, virgin females. These conclusions are compared to a recent analysis of butterfly mating systems by Odendaal et al. (Am. Nat. 125: 673–678, 1985).     

Developmental studies on two ecdysone deficient mutants ofDrosophila melanogaster

Summary This paper describes two ecdysone-deficient, recessive-lethal mutants,lethal(1)giant ring gland (grg) andlethal(1)suppressor of forked ^mad-ts (mad-ts: Jürgens and Gateff 1979) and compares their ecdysteroid titers with that of the wild-type. Mutant larvae show a much reduced ecdysteroid content, amounting to 1/10 to 1/30 of the wild-type values, but never a true titer peak. They fail to pupate and die after 1–3 weeks. Ecdysteroid feeding elicits different responses in the larvae of the two mutants.mad-ts larvae pupate within 24 h, thus showing that their low ecdysteroid titer is directly connected to their inability to pupate.mad-ts resembles the mutantlethal (3)ecdysone-1 ^ts (Garen et al. 1977). Thegrg mutant larvae, on the other hand, fail to pupate after 20-hydroxyecdysone feeding as well as injection. The primary defect of thegrg mutant is not entirely clear. Thegrg larval salivary gland cells appear to possess normal ecdysteroid receptors. Furthermore, the low ecdysteroid titer ingrg is not the result of an increased ecdysteroid catabolism. The primary defect in the mutant may lie in the malfunctioning neurosecretory cells which do not show neurosecretion in histological preparations. Further support for this notion comes from electronmicrographs of the enlargedgrg ring glands which, in contrast to the wild-type, do not possess nerve endings.In the wild-type three ecdysteroid peaks were found: one shortly before puparium formation, the second at approximately 12 h and the third at about 30 h after pupation. The ecdysteroid titer peak in late third instar, wild-type larvae is mainly due to the presence of 20-dydroxyecdysone as shown by radioimmunoassays after thin layer chromatography and derivatization followed by gas liquid chromatography and mass spectroscopy. In addition, a number of unidentified polar and apolar metabolites were also present.     

Effects of photoperiod and temperature on the termination of diapause in the univoltine seed wasp Eurytoma plotnikovi

Abstract Mummified pistachios containing fully grown diapause larvae of Eurytoma plotnikovi Nikol'skaya (Hym., Eurytomidae) were collected in early August and late September in coastal northern Greece and subjected to various photoperiod and temperature treatments, then maintained at 19 or 26°C and a long-day (LD 16:8 h), a changing, or a short-day (LD 10:14 h) photoperiod until pupation. In larvae of early August (beginning of diapause) subjected for 20 weeks to 19°C under a long, a changing, or a short photophase, followed by 19°C and a long photophase, 50% of the larvae pupated after 24, 18 and 13 weeks respectively. After exposure for 20 or even 12 weeks to a short photophase and low temperatures (10 or 4°C), pupation occurred after only 7–8 weeks and was more synchronous. The ranges of temperature for diapause development and post-diapause morphogenesis overlap. After exposure for 12 weeks to short days and low temperature, larvae of late September pupated much sooner under long days than under short days and sooner at 26° than at 19°C. E.plotnikovi depends on both temperature and photoperiod for diapause development, low temperature having a strong favourable effect on the earlier part and long day on the later part of diapause. In a few larvae of another pistachio seed wasp, Megastigmus pistaciae Walker, after a long enough period of low temperatures, diapause was terminated normally at 26°C and long days, or at 19°C and long or short days.     

Prepupal diapause synchronizes adult emergence in the pine processionary moth Thaumetopoea pityocampa (Lepidoptera: Notodontidae)

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Movement and feeding patterns of Epilachna cucurbitae Richards (Coleoptera:Coccinellidae) on pumpkin and zucchini plants2

The oviposition patterns of adults and the movement and feeding patterns of larvae of Epilachna cucurbitae on two species of cucurbits, Cucurbita maxima cv Queensland Blue and C. pepo cv Blackjack, were studied in the field and laboratory. The physical and nutritional characteristics of host plant leaves of different ages were described. Younger leaves had higher nitrogen contents but were less abundant, smaller and had higher trichome densities than older leaves. The development of first instar larvae was delayed by the leaf hairs on young and mature pumpkin leaves which prevented larvae from reaching the leaf surface to feed First instal larvae developed more quickly on leaves rich in nitrogen. Neither the total developmental time of larvae nor the size of pupae was affected by leafage because larvae on poor quality leaves compensated by eating more. Female beetles oviposited on all but the youngest and oldest leaves of the host plant. The trichomes on young leaves prevented females from attaching eggs to the leaf surface. First instar larvae remained where they hatched, but older larvae were more mobile, Changing feeding sites frequently and moving progressively to younger, more nutritious leaves. Final instar larvae moved onto adjacent vegetation to pupate. The adaptive significance of these patterns is discussed in relation to the nutritional value, hairiness and abundance of host plant leaves of different ages and the physical limitations of different larval instars.     

Influence of plant species and plant growth stage on Frankliniella occidentalis pupation behaviour in greenhouse ornamentals

The influence of plant stage and plant species on the pupation behaviour of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), was investigated in flowering and non‐flowering potted chrysanthemums and mini roses. On non‐flowering chrysanthemums and roses, 92–93% of the F. occidentalis pupated in the soil. On flowering roses, 87% pupated in the soil, and on flowering chrysanthemums only 60% chose the soil as a pupation site and 40% stayed on the plant. This means that, in the presence of flowers, especially complex inflorescences like chrysanthemums, a large proportion of F. occidentalis chooses stay on the plant to pupate.