Host-plant susceptibility to the carrot fly, Psila rosae. 2. Suitability of various host species for larval development

Several apiaceous and two asteraceous species were tested for their suitability to support larval development of the carrot fly. Plants grown in pots or transplanted from seed beds into pots, were inoculated with a specific number of eggs. Pupae and non-pupated larvae were collected 6–7 wk after inoculation. Both the number and weights of pupae produced varied widely among the species. Cultivated carrots Daucus carota sativus often gave rise to only moderate numbers of pupae, but these invariably attained the highest weights. Pimpinella major was the only apiaceous plant tested that did not yield any carrot flies. The two asteraceous plants Cichorium intybus and Tanacetum vulgare failed to support larval development. Total carrot fly biomass produced per plant was influenced by both the host species and the root weight. Emergence rates of adult flies were positively correlated with pupal weights. Small individuals tended to have a longer total developmental time from egg to adult fly.     

Host suitability of a gregarious parasitoid on beetle hosts: flexibility between fitness of adult and offspring

Behavioral tactics play a crucial role in the evolution of species and are likely to be found in host-parasitoid interactions where host quality may differ between host developmental stages. We investigated foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi in relation to two distinct host developmental stages: larvae and pupae. Two colonies of parasitoids were reared on larvae of Monochamus alternatus and Saperda populnea (Cerambycidae: Lamiinae). Paired-choice and non-choice experiments were used to evaluate the preference and performance of S. harmandi on larvae and pupae of the two species. Foraging decisions and offspring fitness-related consequences of S. harmandi led to the selection of the most profitable host stage for parasitoid development. Adult females from the two colonies oviposited more quickly on pupae as compared to larvae of M. alternatus. Subsequently, their offspring development time was faster and they gained higher body weight on the pupal hosts. This study demonstrates optimal foraging of intraspecific détente that can occur during host-parasitoid interactions, of which the quality of the parasitism (highest fitness benefit and profitability) is related to the host developmental stage utilized. We conclude that S. harmandi is able to perfectly discriminate among host species or stages in a manner that maximizes its offspring fitness. The results indicated that foraging potential of adults may not be driven by its maternal effects, also induced flexibly with encountering prior host quality.     

Trabala Vishnou Gigantina Yang (Lepidoptera: Lasiocampidae) Larval Fitness on six Sympatric Plant Species in Sea-Buckthorn Forest

Trabala vishnou gigantina Yang (Lepidoptera: Lasiocampidae) is a major pest that damages the sea-buckthorn, Hippophae rhamnoides. We observed and compared the feeding preferences of T. vishnou gigantina larvae on six sympatric plant species in a two-choice test. We also compared T. vishnou gigantina fitness, as measured by the following variables: larvae weight, developmental period, pupae versus adult weight, longevity, and fecundity rates. Between host and non-host plants, larvae showed a strong preference for their natural host (sea-buckthorn), followed by apricot, poplar, and willow. Caragana and locust were the least preferred plants when the natural host plant was not present. Larvae reared on sea-buckthorn possessed greater pre-pupal weight, had lower mortality, and developed more quickly into heavier pupae than either poplar-raised or willow-raised larvae. Fecundity was highest on sea-buckthorn, second highest on apricot, and lowest on poplar. Longevity (of both females and males) was not significantly different across plant species. These results clearly demonstrate that T. vishnou gigantina larvae are able to distinguish between host versus non-host plants, and that their preference translates to increased fitness. Possible, non-mutually exclusive explanations for observed preference and fitness differences include variation in required nutritional content across plant species or the presence of plant traits (morphological features or chemical metabolites) that negatively affect larval development. While the exact mechanisms are unknown, these data may be useful for the development of appropriate counter-measures to the damage caused by T. vishnou gigantina on sea-buckthorn.     

Spatial dynamics of lepidopterous pests on Zea mays (L.) and Pennisetum purpureum (Moench) in the forest zone of Cameroon and their implications for sampling schemes

The most common lepidopterous borers attacking maize and/or the wild host Pennisetum purpureum in the forest zone of Cameroon are the noctuids Busseola fusca (Fuller), Sesamia calamistis (Hampson) and Poeonoma serrata (Hampson), the pyralids Eldana saccharina (Walker) and Mussidia nigrivenella (Ragonot), and Cryptophlebia leucotreta (Tortricidae). The within-plant distribution on maize and elephant grass was studied for the predominant species B. fusca , and on maize only for E. saccharina to determine the basic sampling unit. On both plant species, B. fusca showed a strong oviposition preference for young plant parts. By contrast, E. saccharina larvae and pupae on maize were only found on older plant parts indicating that it does not oviposit on young plants. No part of the plant strata appeared to be a stable sampling unit and it is recommended to carry out whole plant or whole tiller sampling for maize and grass, respectively. For the development of sampling plans, dispersion was described for all species using Taylor's power law and a non-linear model which gives the relationship between the proportion of infested plants [ P ( I )] and mean density ( m ). Busseola fusca egg batches as well as diapausing larvae and pupae on maize showed a random distribution whereas all the other cases were aggregated, with B. fusca egg batches on elephant grass exhibiting the lowest and M. nigrivenella on maize the highest aggregation. Optimal sample size/mean density curves were developed for groups of insects with low and high aggregation.     

不同寄主植物对三条橙灯蛾生长发育和繁殖的影响

在室内条件(温度(26±1)℃,相对湿度80%,光周期12L∶12D)下研究了天仙果(Ficus erecta Thunb.var.beecheyana(Hook.et Arn.)King)、大青(Clerodendrum cyrtophyllum Turcz)、华东油柿(Diospyros oleiera Cheng)、喜树(Camptotheca acuminate Decne)和杨梅(Myrica rubra(Lour.)Sieb.et Zucc)5种不同科的寄主植物对三条橙灯蛾Lemyra alikangensis(Strand)取食偏好、生长发育、繁殖及营养效应的影响。结果表明,三条橙灯蛾对不同寄主植物表现出明显的取食选择差异;不同寄主植物对三条橙灯蛾的幼虫发育历期、累计存活率、产卵量及营养效应等指标均有显著影响。三条橙灯蛾4龄幼虫偏好取食大青,对杨梅和喜树的选择率很低。幼虫历期以大青饲喂组最短为(39.20±1.79)d,杨梅饲喂组最长为(48.25±2.22)d;累计存活率以大青饲喂组最高(45.71%),杨梅饲喂组最低(28.57%);大青饲喂组产卵量最多为(553.75±61.69)粒/雌,杨梅饲喂组最少为(386.25±51.05)粒/雌。大青饲喂组三条橙灯蛾的相对生长率(0.30±0.03)mg·mg-1·d-1、食物利用率(13.46±1.84)%、近似消化率(62.04±6.29)%在各组中均最高,但食物转化率(21.65±0.95)%很低;杨梅饲喂组三条橙灯蛾的相对生长率(0.12±0.03)mg·mg-1·d-1、近似消化率(14.75±1.48)%很低,但是食物利用率(5.41±0.61)%较高,食物转化率(36.79±4.07)%最高。综合各指标认为:在5种供试植物中大青是三条橙灯蛾的最适寄主植物,杨梅则最不利于其生长发育和种群繁衍。     

多异瓢虫食物消耗与利用与其猎物棉蚜的寄主植物种类相关

【目的】猎物质量和类型在捕食者食物选择、消耗及营养转化过程中起着重要作用,植物的营养质量影响植食者的营养质量,进而植食者作为捕食者猎物的营养质量。为进一步了解植物-猎物-捕食者三营养层的相互作用,研究了寄主植物对捕食者食物消耗与利用的影响。【方法】在室内评价了多异瓢虫Hippodamia variegata (Goeze) 4龄幼虫和雌成虫取食和利用 5种不同葫芦科植物上的棉蚜 Aphis gossypii Glover的效率。【结果】多异瓢虫4龄幼虫和成虫均对南瓜Cucurbita moschata var. melonaeformis上的蚜虫取食量最高,而对瓢葫芦Lagenaria siceraria var. gourda上的蚜虫取食量最低。4龄幼虫取食哈密瓜 Cucumis melo var. cantalupensis上的蚜虫时,其相对生长率、食物利用率和食物转化率均达到最大,而雌成虫在取食黄瓜Cucumis sativus和搅瓜Cucurbita pepo var. medullosa上的蚜虫时,其相对生长率不存在显著差异,在取食黄瓜、瓢葫芦和搅瓜上的蚜虫时,其食物利用率和食物转化率也不存在显著差异。因此,哈密瓜上的瓜蚜更适宜作为多异瓢虫4龄幼虫的猎物,而黄瓜、瓢葫芦和搅瓜上的瓜蚜更适宜作为成虫的猎物。【结论】寄主植物种类与多异瓢虫对棉蚜的捕食效率相关,该结论为进一步利用昆虫的食性对害虫进行控制奠定理论基础。     

Coevolution of the checkerspot butterfly Euphydryas chalcedona and its larval food plant Diplacus aurantiacus: larval response to protein and leaf resin

Summary Prediapause larvae of the checkerspot butterfly Euphydryas chalcedona were raised from hatch until entrance into diapause on artificial diets. The proportions of protein and host plant leaf resin differed among the diets. Larval size growth rates and mortality were monitored and overall rates and efficiencies of food use were computed.Larval survivorship, growth rate and size of larvae at idapause were significantly enhanced by increasing dietary protein content, particularly over the range found in leaves of the host plant. In contrast, an increasing dietary content of Diplacus aurantiacus leaf resin significantly depressed larval surviviorship, growth rates and size of larvae at diapause. A simple dosedependent interaction was observed between the effects of dietary leaf resin and protein on larval success. Dietary content of leaf resin and protein significantly influenced some measures of food utilization efficiency (ECI and ECD), but not others (AD and NUE).The negative interaction between the effects of dietary leaf resin and protein content suggests the leaf resin phenolic compounds reduce the availability of protein to the larvae. The results for efficiency indices of larval food use are potentially in conflict with this interpretation.The influence of host plant leaf resin and protein on larval success, coupled with the relation between photosynthesis and leaf nitrogen content, are consistent with the hypothesis that productivity can be enhanced by herbivore deterrence resulting from leaf resin production.     

Dispersal of first-instar gypsy moth larvae in relation to population quality

Summary Field studies of dispersal by first instar gypsy moth larvae indicate that almost all larvae undergo an initial dispersal episode. However, in laboratory studies large larvae (from large eggs) disperse more frequently than small larvae (from small eggs) in the presence of favored food. Large larvae may be better adapted for dispersal. When larvae encounter unacceptable food or are denied food, larvae disperse more frequently and dispersal by small larvae is nearly as frequent as dispersal by large larvae. Factors affecting egg size may contribute to shifts in dispersal patterns of gypsy moth larvae and distribution of populations.Paper No. 2041, Massachusetts Agricultural Experiment Station, University of Massachusetts at Amherst. This research supported (in part) from Experiment Station Project No. 355     

Clutch size in a larval-pupal endoparasitoid

Clutch size decisions by Aphaereta minuta (Nees) (Hymenoptera: Braconidae), a polyphagous, gregarious, larval-pupal endoparasitoid, were studied under laboratory conditions. This parasitoid attacks larvae of Diptera inhabiting ephemeral microhabitats such as decaying plant and animal material. Females oviposit in young larval stages, but the eventual size of the host pupa determines host food availability for competing offspring. The size of the pupa can differ greatly between host species. We questioned how A. minuta females deal with this delay between the moment of oviposition and eventual host food availability, and whether they make clutch size decisions that benefit their fitness. It was shown that females indeed vary their clutch size considerably and in an adaptive way: (1) females lay larger clutches in larvae of host species that produce larger pupae, even when the larvae are the same size at the moment of oviposition, and (2) females lay larger clutches in larger larvae than in smaller larvae of the same host species. The latter seems functional as larvae parasitized at an older stage indeed developed into larger pupae compared to larvae parasitized at a younger stage. Furthermore, mortality of parasitized young host larvae was greater than that of both unparasitized larvae and parasitized older larvae. Under field conditions the risk of mortality of young host larvae is expected to be even higher due to the limited period of microhabitat (host food) availability, strong scramble type competition between the host larvae, and the longer period of being exposed to predation.     

Natural and artificial envenomation of Ceratitis capitata by Eupelmus urozonus and the search for new bioinsecticides

This study was designed to indentify novel bioactive molecules in the venom of the parasitoid Eupelmus urozonus Dalman (Hymenoptera: Eupelmidae). Parasitism by E. urozonus induces apparent paralysis in the larvae of the host Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and it arrests the development of host pupae. Parasitoid eggs were transferred from stung to unparasitized host pupae to determine whether adult female stings or bites from the first instars were responsible for the above effects. The two treatments gave the same results, indicating that both parasitoid adults and larvae produced venoms capable to compromise host development. A protocol was developed to artificially microinject E. urozonus venom into healthy host pupae and adults at known concentrations to study the effects. The microinjection of venom was found to produce the same macroscopic result as natural parasitization, indicating that host developmental arrest was caused by molecules produced by the parasitoid venom glands. One‐tenth, one‐twentieth, and one‐hundredth of the contents of a female venom reservoir was sufficient to compromise the development of 100, 90, and 50% of the microinjected host pupae, respectively. The microinjection of 0.1 female venom equivalents into host adults always caused death within 24 h. Extraction and freezing did not affect the activity of the E. urozonus venom, which facilitates its storage, whereas denaturation treatments demonstrated that the bioactive molecules were proteins. The venom was also found to prevent the hosts from decaying for over 2 weeks and it promoted the accumulation of unknown subspherical granules in the host haemocoel. These results suggest the potential identification of novel molecules with interesting biological activity with various possible applications.     

Effects of host stages and temperature on population parameters of Oomyzus sokolowskii, a larval-pupal parasitoid of Plutella xylostella

Oomyzus sokolowskii is alarval-pupal parasitoid of diamondback moth, Plutella xylostella. In a host stage preference test, the parasitoid parasitised all larval and pupal stages, but exhibited a strong preference for larvaeover prepupae or pupae, and did not show a preference among the larval instars. At 25°C, the developmental time, number and sex ratio of offspring per host pupa, and successful parasitism did not differ significantly among parasitoids reared from host larvae of different instars, indicating similar host suitability between larvae of different instars. Mean developmental times from egg to adult at 20, 22.5, 25, 30, 32.5, and 35°C were 26.5,21.0, 16.0, 12.7, 11.9 and 13.4 days, respectively. The favourable temperature range for development, survival, and reproduction of the parasitoid was 20--30°C. However, wasps that developed and emerged at a favourable temperature could parasitise effectively at 32--35°C for 24 hours. Life-fertility table studies at 20, 25, and 30°C showed that each female wasp on average parasitised 3.1, 13.2, 6.8 larvae of diamondback moth and produced 20.5, 92.1, 50.4 offspring, respectively, during her lifetime. The highest intrinsic rate of natural increase (r _m) of 0.263 female/day was reached at 30°C as a result of the short mean generation time at this temperature compared to that at 20 and 25°C, suggesting that the parasitoid had the highest potential for population growth at relatively high temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Host plant exodus and larval wandering behaviour in a butterfly: diapause generation larvae wander for longer periods than do non‐diapause generation larvae

1. Prior to pupation, lepidopteran larvae enter a wandering phase lasting up to 30 h before choosing a pupation site. Because stillness is important for concealment, this behaviour calls for an adaptive explanation. 2. The explanation most likely relates to the need to find a suitable pupation substrate, especially in terms of shelter from predation, and given that many predators and parasitoids use host plants as prey‐location cues, mortality probably decreases with distance from the host plant. Hence, remaining on the host includes a long‐term risk, while moving away from the host introduces an increased risk during locomotion. 3. Bivoltine species that overwinter in the pupal stage produce two kinds of pupae; non‐diapausing pupae from which adults emerge after 1–2 weeks, or diapausing pupae that overwinter with adults emerging after 8–10 months. 4. Given the hypothesis of distance‐from‐host‐plant‐related predation, this should select for phenotypic plasticity with larvae in the diapausing generation having a longer wandering phase than larvae under direct development, if there is a trade‐off between mortality during the wandering phase and accumulated mortality during winter. 5. Here this prediction is tested by studying the duration of the wandering period in larvae of the partially bivoltine swallowtail butterfly, Papilio machaon, under both developmental pathways. 6. The results are in agreement with the predictions and show that the larval wandering phase is approximately twice as long under diapause development. The authors suggest that the longer duration of the wandering phase in the diapause generation is a general phenomenon in Lepidoptera.     

棉铃虫在4个辣椒品种上的寄主适合度

在室内条件下,比较了棉铃虫幼虫对辣味程度依次下降的豫优鲜辣2号、豫艺绿冠、豫艺墨秀大椒和豫甜椒12号4个辣椒品种果实的嗜食性、食物转化率和利用率及种群增长情况。结果表明：（1）棉铃虫幼虫的取食选择性、对食物的近似消化率和利用率在4个辣椒品种之间存在明显差异。其中初孵、3龄和5龄幼虫对4个辣椒品种果实的选择性规律基本一致,在豫甜椒12号品种上幼虫出现的百分率和取食量比率均最大;随着辣椒品种辣味程度的降低,5龄幼虫在其上的取食时间和休息时间依次增加,活动时间则依次降低;取食4个辣椒品种的果实后,6龄幼虫的相对生长率、相对取食量和食物转化率差异不显著,但取食豫甜椒12号与豫优鲜辣2号和豫艺绿冠之间的近似消化率和食物利用率差异达显著水平。（2）室内271 ℃ 、70 %-80 % RH和16 L：8 D光周期条件下,棉铃虫在4个辣椒品种上均能完成其世代周期,随着辣椒品种辣味程度的增加,1龄幼虫和整个世代的发育历期依次延长,且在豫甜椒12号与豫优鲜辣2号之间差异达显著水平。其中在豫优鲜辣2号上棉铃虫的世代发育历期最长（27.86 d）,其次为豫艺绿冠（27.23 d）,再次为豫艺墨秀大椒（26.83 d）,在豫甜椒12号上的发育历期最短（25.85 d）;棉铃虫在4个辣椒品种上的世代存活率分别为豫优鲜辣2号为21.67%、豫艺绿冠为23.33%、豫艺墨秀大椒为23.33%、豫甜椒12号为35.00%;取食4个品种辣椒后,棉铃虫的蛹重差异不显著,其中雌蛹重分别为取食豫甜椒12号品种的为249.3 mg,取食豫艺墨秀大椒的为244.7 mg,取食豫艺绿冠的为243.4 mg,取食豫优鲜辣2号的雌蛹最轻,为209.4 mg。雄蛹重与雌蛹表现出的规律基本一致,但取食同一品种的雌蛹重均高于雄蛹重。（3）棉铃虫的种群净增殖率和内禀增长率在豫优鲜辣2号品种上最低,在豫甜椒12号品种上最高。以上结果表明,随着4个辣椒品种辣味程度的增加,棉铃虫在其上的寄主适合度则依次降低,其寄主适合度顺序为：豫甜椒12号＞豫艺墨秀大椒＞豫艺绿冠＞豫优鲜辣2号。     

Influence of Liriomyza species (Diptera: Agromyzidae) and their host plants, on oviposition by Opius dissitus females (Hymenoptera: Braconidae)

Two factors, among others, influence the oviposition of Opius dissitus Muesebeck. The first was the host species, the second the plant upon which the pest host larvae develop. O. dissitus females prefer Liriomyza trifolii (Burgess) larvae over those of L. huidobrensis (Blanchard). O. dissitus females were more attracted to the larvae of L. trifolii or L. huidobrensis when these were present on courgette rather than tomato or lettuce.     

Effects of larval host plants on over-wintering physiological dynamics and survival of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Laboratory colonies of cotton bollworm larvae, Helicoverpa armigera, were kept at 20 °C under a photoperiod of L:D = 10:14 and fed on three host plants (cotton, tobacco, kidney bean) and an artificial diet (control) to determine the dynamic effects of larval host quality on over-wintering physiology and mortality. Energy reserves (glycogen and lipid), super-cooling points (SCPs), low-molecular-weight sugars, temperature, and mortality were monitored from November 2002 to April 2003. Lipid content did not change much for each group during over-wintering, but differed according to larval host plants. Larval host plants obviously influence the amount of glycogen, as does time of year: glycogen was lowest in February and increased in early spring. During winter, the mean pupal SCPs increased the most in February, then decreased, and were also affected by larval host plant, i.e. over-wintering pupae reared on kidney bean had the highest SCPs. Levels of glycerol and inositol differed significantly among host plants and months, which peaked in February. Pupal mortality also varied according to larval host plants and time: pupae reached their highest mortality in March and showed host plant differences in January. Records show that February was the coldest month during the period we observed, which corresponded closely to changes in over-wintering characteristics.     

Temperature-dependent post-diapause development and prediction of spring emergence of the pine needle gall midge (Dipt., Cecidomyiidae)

Abstract:  We determined the influence of temperature on post-diapause development of overwintered Thecodiplosis japonensis Uchida et Inouye (Dipt., Cecidomyiidae) under various treatments (12, 15, 18, 21, 24, 27 and 30°C) in an effort to predict its spring emergence. Survival and developmental period for the overwintered larvae and pupae were significantly influenced by temperature. Linear and nonlinear regression models quantitatively described temperature-dependent development and survival of T. japonensis . The survival models exhibited right-skewed bell shape patterns for all stages, indicating a more detrimental impact on survival at high temperatures. Theoretical optimum temperatures with highest survival were 22.3, 24.0 and 24.0°C for the overwintered larvae, pupae and total post-diapause development (the larvae to adults) respectively. Pupal mortality was higher at all temperatures than larval mortality and the suitable range of temperature for pupae was narrower than that of larvae. The nonlinear Briere model estimated that optimum temperatures with the fastest development were 29.1°C for larvae, 27.6°C for pupae and 27.0°C for larvae to adults. In a linear model, the lower threshold temperatures were 5.1, 7.1 and 5.9°C for larvae, pupae, and larvae to adults respectively. A predictive degree-day model was developed using trap catches of T. japonensis adult emergence during 1991–1995. The model accounted for 84.6% of year-to-year variation in adult emergence and predicted accurately the median emergence time in 1996.     

Biology of Cuterebra lepusculi Townsend (Diptera: Cuterebridae) in cottontail rabbits in Idaho

Cuterebra lepusculi Townsend parasitize cottontail rabbits (Sylvilagus nuttallii) in southern Idaho. Peak parasitism was 69% in mid-September. Mean development time in the host was 27 days. The species is univoltine in Idaho. Partially developed larvae were transferred from freshly killed to living hosts and the resulting larvae matured normally. Developing pupae were cooled or warmed to retard or speed development and synchronize adult emergence.     

Cultivated and wild host plants supporting populations of the cabbage root fly

To determine the relative importance of different potential host plants for supporting populations of the cabbage root fly, wild and cultivated crucifers were sampled for pupae at four locations during 1971-3. In addition, eighty-three species of Cruciferae native to or naturalized in the British Isles were inoculated with cabbage root fly eggs in a glasshouse to determine which species could support the larvae. In the field, most pupae (28-7/plant) were collected from untreated cauliflowers. Fewer pupae (i-7–8-6/plant) were obtained from untreated crops of Brussels sprout, cabbage and swede. Applications of chlorfenvinphos reduced populations to two or less pupae per plant on all crops. Of five common weed species sampled, only Raphanus raphanistrum produced as many pupae as certain of the untreated brassica crops. Pupae did not occur in samples from Capsella bursa-pastoris but Sisymbrium officinale, Thlaspi arvense and Sinapis arvensis usually supported low numbers. In the glasshouse, only forty-four of the eighty-three cruciferous species tested supported larval development. Most pupae were obtained from 12-wk-old plants of Barbarea intermedia. B. stricta, Brassica napus, Cochlearia officinalis and R. raphanistrum and from 24-wk-old plants of Brassica rapa, Erysimum aureum, Cochlearia anglica and C. officinalis. Plant age considerably affected pupal production. Plants within a genus often gave similar results, pupae not being recovered from any of the Diplotaxis or Arabis species tested, or from young plants of Erysimum spp. In other families, Reseda lutea and R. luteola supported larval development, but the widely-separated Plantago major did not. Arguments for and against the removal of cruciferous weeds from the vicinity of cruciferous crops are discussed.     

Chemical profiling of polyphenols in extracts from bark of Acacia nilotica (Linn.) and their efficacy against Spodoptera litura (Fab.)

Six different crude extracts from bark powder of an important medicinal plant, Acacia nilotica (L.) were investigated for their toxicity against Spodoptera litura (Fab.). Total phenolic content in six crude extracts was measured. Ultra-High Performance Liquid Chromatography (UHPLC) was also performed for qualitative analysis of six crude extracts which revealed the presence of 11 phenolic compounds. Bioassays conducted with all crude extracts revealed maximum adverse effect with acetone extract. Duration of larval period and total development period was found to be prolonged. Various aberrations were observed in pupae and adults in the form of wrinkled pupae, blackened pupae, bulged out head part of pupae, partially emerged adults and adults with crumpled wings. All nutritional indices viz. RGR, RCR, ECI, ECD and AD decreased with treatment. The findings indicated that A. nilotica had considerable potential in the management of this serious insect pest.     

Some aspects of the host:parasite relationships between adult blackflies (Diptera; Simuliidae) and larvae of the water-mite Sperchon setiger(Acari; Hydrachnellae) in a small chalk stream in southern England

SUMMARY. In Bere Stream three species of adult simuliids, S . ornatum, S. equinum and S. angustipes were parasitized by Sperchon setiger larvae. Trapped adult S. ornatum were more often parasitized than corresponding adults of S. equinum. The lower 95% confidence limits were used as an indication of the relative importance of the statistically significant differences and were high (10.4–33.6%). Laboratory experiments on the occupation of host pupae by pre-parasitic Sperchon setiger larvae also indicated that pupae of S. ornatum were more often occupied than S. equinum. This was confirmed by tests on the difference in percentage occupation of more than 4000 held-collected host pupae. In tests that indicated a significant difference in percentage parasitization between the sexes of the three host species, females were more often parasitized. However, the lower 95% confidence limits for the increase in percentage parasitization of females compared to males were low (0.9–10.2%). The majority of adult simuliids carried only one parasite. The mean number of larvae per trapped parasitized host was significantly greater for S. ornatum (2.69) than for S. equinum (1.77). There was no significant difference between the mean number of parasites carried by the sexes of S. ornatum for each year from 1975 through 1978 but females were significantly more heavily parasitized than males during 1979. The ventral neck region of all three host species is the main attachment site for Sperchon setiger larvae.
The morphology of the pupae of S. ornatum and S. equinum is related to differences in levels of percentage parasitization between these two species. It is suggested that pupal morphology may be the most important factor in the selection of host simuliids by Sperchon setiger larvae.