Showing papers on "Lepidoptera genitalia published in 1996"

What causes population cycles of forest Lepidoptera

Abstract: Hypotheses for the causes of regular cycles in populations of forest Lepidoptera have invoked pathogen-insect or foliage-insect interactions. However, the available data suggest that forest caterpillar cycles are more likely to be the result of interactions with insect parasitoids, an old argument that seems to have been neglected in recent years.

Sex Chromatin in Lepidoptera

Abstract: Like mammals, Lepidoptera possess female-specific sex chromatin. In a compilation of new and published data, 81 % of the 238 investigated Lepidoptera species display one or more heterochromatin bodies infemale somatic interphase cells, but not in male cells. In contrast with the similar phenomenon in mammals, this sex-specific heterochromatin does notfunction as a dosage compensation mechanism. Most Lepidoptera have a WZ/ZZ sex chromosome mechanism, and the sex chromatin is derived from the univalent W sex chromosome. Sex chromatin is regarded as an indicator of an advanced stage of Wchromosome evolution. In species with a Z/ZZ sex chromosome mechanism, loss of the Wchromosome is accompanied by loss ofthefemale-specific heterochromatin. Since sex chromatin can be discerned easily in interphase nuclei, and especially so in the highly polyploid somatic cells, it is a useful marker for diagnosing chromosomal sex of embryos and larvae, and of identifying sex chromosome aberrations in mutagenesis screens. All species with sex chromatin belong to theDitrysia, the main clade of Lepidoptera that contains more than 98 % of all extant species. Sex chromatin has not been reportedfor clades that branched off earlier. The nonditrysian clades share this character with Trichoptera, a sister group of the Lepidoptera. We propose that Lepidoptera originally had a Z/ZZ sex chromosome mechanism like Trichoptera; the WZ/ZZ sex chromosome mechanism evolved later in the ditrysian branch of Lepidoptera. Secondary losses of the W chromosome account for the sporadically occurring Z/ZZ sex chromosome systems in ditrysianfamilies. The lepidopteran sex chromatin, therefore, appears to mirror thefull evolutionary life cycle of a univalent sex chromosomefrom its birth through heterochromatinization to sporadic loss.

Effects of Bacillus thuringiensis Berliner var. kurstaki and defoliation by the gypsy moth [Lymantria dispar (L.) (Lepidoptera: Lymantriidae)] on native arthropods in West Virginia

Abstract: Impacts of Bacillus thuringiensis var. kurstaki (Btk) and defoliation by gypsy moth [Lymantria dispar (L.)] on native, non-target arthropods were evaluated in eastern West Virginia from 1990 to 1992. Adult and larval arthropods were collected by foliage sampling and light-trapping at 24 20-ha (50-acre) plots, representing six replicates of four treatments: unsprayed, gypsy moth absent (control); unsprayed, gypsy moth present (defoliation); sprayed, gypsy moth absent; and sprayed, gypsy moth present. Pre-treatment data were collected in 1990. In May 1991, one application of Btk was made to 12 plots at a dosage of 14.4 BIU/ha (36 BIU/acre). Post-treatment data were collected in 1991 and 1992. With few exceptions, detectable effects from Btk application were restricted to Lepidoptera. Although abundance and species richness of larval and adult non-target Lepidoptera decreased at all plots between 1990 and 1992, abundance and species richness were reduced at Btk-treated plots relative to untreated plots. Richness and abundance of some larval and adult Lepidoptera declined at defoliation plots. Although the short-term ( 1 year) of reduced abundance of gypsy moth larvae may be beneficial for some native species. Although Btk application and defoliation reduce abundance of native Lepidoptera, environmental conditions such as weather may have a greater influence on population fluctuations.

Prey selection and baculovirus dissemination by carabid predators of Lepidoptera

Abstract: . 1 The interaction between coleopteran predators and baculovirus-infected larvae was studied in the laboratory and the field in order to assess the potential role of predators in the dissemination of a nucleopolyhedrovirus (NPV). 2 Preference tests using three carabid species, Harpalus rufipes De Geer, Pterostichus melanarius Illiger and Agonum dorsale Pont, showed no evidence of discrimination between healthy and diseased larvae of the cabbage moth Mamestra brassicae L. (Lepidoptera: Noctuidae) as prey items. 3 Virus infectivity was maintained after passage through the predator's gut. NPV mortality ranged from 97% to 20% when test larvae were exposed to faeces collected immediately after and 15 days post-infected meal respectively. 4 The potential for transfer of inoculum in the environment was estimated in the laboratory by soil bioassay. Carabids continuously passed infective virus to the soil for at least 15 days after feeding on infected larvae. 5 Field experiments showed that carabids which had previously fed on diseased larvae transferred sufficient virus to the soil to cause low levels of mortality in larval populations of the cabbage moth at different instars.

Reproductive Capacity of Laboratory-Reared Gypsy Moths (Lepidoptera: Lymantriidae): Effect of Age of Female at Time of Mating

Abstract: The reproductive potential of laboratory-reared gypsy moths, Lymantria dispar (L.), was studied as a function of female age at time of mating. The parameters studied were number of eggs produced, number of eggs deposited, mating, sperm transfer, egg viability, and female longevity. Delayed mating did not affect female longevity, but all other factors decreased with increased age at time of mating. With increasing age, females were less likely to mate or receive a full complement of sperm than females exposed to males within the first few days after eclosion. Females that oviposited before being placed with males were less likely to mate than those that had not. For females receiving a full complement of sperm, the number of eggs produced, the number laid, and egg viability decreased with increasing age of the female at mating. Overall, a delay in mating of 3-5 d reduced the reproductive potential of females from 40 to 90% of that of females mated within the first 36 h.

Effects of ultraviolet-B exposure of Arabidopsis thaliana on herbivory by two crucifer-feeding insects (Lepidoptera)

Abstract: Larvae of Pieris rapae (L.) (Lepidoptera: Pieridae) and Trichoplusia ni (Huebner) (Lepidoptera: Noctuidae) were fed foliage from Arabidopsis thaliana (L.) Heynh. plants that had received a high dose of ultraviolet-B (UV-B) or from control plants. Treatments were compared using the Student independent t-test. P. rapae larvae consumed less of the foliage exposed to UV-B than control foliage. This difference as significant in older but not younger larvae, and the older P. rapae larvae fed foliage exposed to UV-B weighed significantly less. For T. ni, however, consumption and larval weights were approximately equal for UV-exposed and control foliage. No significant differences in growth rates per unit consumption on UV-exposed versus control foliage were found for either species. Chemical analysis showed that flavonoid levels increased in response to UV-B. Results suggested that UV-inducible flavonoids may act as feeding deterrents to P. rapae but not to T. ni. 56 refs., 6 figs.

Natural history and identification of litter‐feeding Lepidoptera larvae (Insecta) in beech forests, Orongorongo Valley, New Zealand, with especial reference to the diet of mice (Mus musculus)

Abstract: New Zealand, in common with Australia and New Caledonia, has 12–19% of its Lepidoptera associated with litter. Elsewhere in the world, reported litter‐feeding is characteristic of less than 5% of the relevant lepidopteran fauna. Studies in the Orongorongo Valley, New Zealand, have shown a coincidence of high numbers of the introduced house mouse (Mus musculus L.), litter‐feeding Lepidoptera, and heavy beech‐seed production. Stomachs from trapped mice commonly contain caterpillar fragments, many of which belong to species feeding on litter. In Orongorongo Valley Nothofagus forest, litter‐dwelling larvae of over 20 moth species attain a body length greater than 10 mm, and hence are attractive to mice. Aspects of their biology are discussed in relation to their availability to mice. The genera most often encountered are Tingena, Gymnobathra (Oecophoridae), Dumbletonius (Hepialidae), Mallobathra, Grypotheca (Psychidae), and Rhapsa (Noctuidae). A key is given to Lepidoptera larvae known to live in litter, and ...

Biology of Trichogramma galloi and T. pretiosum (Hymenoptera: Trichogrammatidae) reared in vitro and in vivo

Abstract: The life cycle and parasitization of Trichogramma galloi Zucchi and T. pretiosum Riley were studied on natural and factitious hosts, and on artificial diets. Eggs of sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Pyralidae), and tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), were used as natural hosts of T. galloi and T. pretiosum , respectively. Eggs of Mediterranean flour moth, Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae), were used as factitious host for both parasitoids. T. galloi was reared in vitro on a diet of 70% hemolymph of larvae of corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), 20% chicken egg-yolk, 10% bovine fetal serum, and 0.2% streptomycin. T. pretiosum was reared on a similar diet, with 5% H. virescens egg juice replacing 5% bovine fetal serum. The egg-adult development of T. pretiosum reared on the artificial diet was delayed, whereas developmental differences were not found for T. galloi reared on natural or artificial diets. Survivorship was also reduced for both parasitoids reared on artificial diets. The parasitization and female longevity were reduced for parasitoids reared on the factitious host or artificial diets. No differences in adult size or in morphology of the genital apparatus were detected among parasitoids reared in vitro or in vivo; but wing and abdominal malformations occurred for parasitoids reared on artificial diets.

Potential Enhancement of the Gypsy Moth (Lepidoptera: Lymantriidae) Nuclear Polyhedrosis Virus with the Triterpene Azadirachtin

Abstract: Second-instar gypsymoth, Lymantria dispar (L.), larvae were placed on semisynthetic diet and white oak, Quercus alba L., seedlings that had been surface-treated with azadirachtin and gypsy moth nuclear polyhedrosis virus. Both treatments affected larval development (weight gain and molting) and survival. When consumed together, larvae died significantly faster compared with larvae, which consumed only azarurachtin or virus. The combination also resulted in lowered larval survival compared with that observed when only 1 material was consumed. The combination of azadirachtin and virus should result in good foliage protection if used against gypsy moth larvae. However, the addition of azadirachtin to viral formulations could also result in less virus being produced within the larval cadaver and released into the environment because the affected larvae are smaller.

α-Amylase Activities in Larval Midgut Extracts from Four Species of Lepidoptera (Tortricidae and Gelechiidae): Response to pH and to Inhibitors from Wheat, Barley, Kidney Bean, and Streptomyces

Abstract: Levels of α-amylase activity between 0.6 and 5.0 µmoles maltose minute-1 gram insect-1 occurred in larval midgut extracts from 4 species of lepidopterous pests-light brown apple moth, Epiphyas postvittana (Walker), Planotortrix octo (Dugdale), and Ctenopseustis Obliquana (Walker) are pests of apple leaves and fruit, and potato tuber moth, Phthorimaea Operculella (Zeller), is a pest of potato tubers and foliage. Activity response curves described the optima for activity at a highly alkaline pH range (pH 10.5 in leafrollers and pH 9.5 in potato tuber moth). This result is consistent with the known high midgut pH in other species of Lepidoptera and with the pH optima of their digestive proteases. The 3 wheat derived α-amylase inhibitors inhibited enzyme activities of all 4 species of Lepidoptera, but the other 3 (barley tetramer, Streptomyces , and kidney bean inhibitors) had no effect. Wheat dimeric inhibitor (30 µM) completely inhibited α-amylase activity in potato tuber moth midgut extracts.

Effectiveness of Larval Defenses Against Spider Predation in Cranberry Ecosystems

Abstract: Two laboratory experiments, a choice test and observations of individual spider-larva interactions, were conducted to determine how the morphological or behavioral defenses, or both, of larvae may affect spider predation success for 2 genera of spiders [Pardosa (Lycosidae), and Habronattus (Salticidae)] commonly found in Massachusetts cranberry, Vaccinium macrocarpon Aiton, ecosystems. Four species of pest larvae with different potential defenses were offered as prey: a spanworm, Ematurga amitaria Guenee (Lepidoptera: Geometridae); a sawfly, Pristophora idiota Norton (Hymenoptera: Tenthridinae); gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae); and a fruitworm, Sparganothis sulfureana Clemens (Lepidoptera: Tortricidae). In the choice tests, E. amitaria larvae were killed significantly more often than either P. idiota or S. sulfureana larvae. No L. dispar larvae were killed in either experiment, and observations suggested that the long setae of the L. dispar larvae provided defense against spider attack. Observations revealed that behavioral and morphological crypsis was a more effective defense than thrashing and regurgitating when E. amitaria larvae were encountered by either genera of spider and also suggested the presence of a chemical defense(s) in P. idiota larvae. Construction of a retreat in cranberry foliage and wriggling movements by S. sulfureana larvae were highly effective in deterring salticid predation. We conclude that the defensive mechanisms possessed by these larvae may effectively influence prey selection and significantly limit predation by spiders in the cranberry agroecosystem.

Oviposition deterrency in pineapple borer females, Thecla basilides (Lepidoptera: Lycaenidae)

Abstract: Selection of suitable oviposition sites contributes to reproductive success of females in the Lepidoptera. Because larvae have limited dispersal ability (Renwick & Chew, 1994), females may maximize their fitness by ovipositing on host plants most suitable for larval development and survival (Myers, 1985; Pilson & Rausher, 1988) or with minimal intraspecific competition (Rausher. 1979). Recognition and rejection of hosts already infested with conspecific eggs or larvae is adaptive, particularly for insects that develop in food resources with limited carrying capacity (Shapiro, 1981), such as fruiting structures of plants (Thompson, 1983; Jones, 1991). Females achieve resource partitioning and avoid overcrowding by ovipositing preferentially on hosts without conspecific eggs (Rothschild & Schoonhoven, 1977; Rausher, 1979; Shapiro, 1981), larval frass (Renwick & Radke, 1980; Dittrick et al., 1983), or plant allelochemicals emanating due to larval feeding (Leather et al., 1987). Female pineapple borers, Thecla basilides Geyer (Lepidoptera: Lycaenidae), oviposit on small, young pineapple fruits (Ananas comosus Menill) (Johnson, 193 1). Emergent larvae penetrate the soft epiderm and complete development within the fruit. Feeding of larvae induces production of a sticky exudate by the fruit. In the present study we have tested the hypothesis that female Tbasilides discriminate between potential hosts and preferentially oviposit on pineapple fruits without conspecific eggs, larval frass or pineapple exudate.

Ectoparasitic acugutturid nematodes of adult lepidoptera.

Abstract: Noctuidonema guyaneme is an interesting ectoparasite of adult Lepidoptera that feeds on hosts from at least five families with its long stylet. Noctuidonema guyanense spends its entire life on the adult moth and is sustained as it is passed from moth to moth during host mating. Overlapping host generations are essential for parasite survival. This nematode occurs throughout tropical and subtropical America and is transported by at least one of its hosts, Spodoptera frugiperda, during migration to northern sites in the United States each spring. Noctuidonema guyanense debilitates its hosts. Research conducted to help determine the biological control importance of this nematode is reviewed. Two additional species, N. daptria and N. dibolia, are now known for Noctuidonema.

An unusual behavior inHelicoverpa armigera Hübner (Lepidoptera: Noctuidae): Pupation inside tomato fruits

Abstract: Helicoverpa armigera Hb. is a cosmopolitan noctuid species, widespread in Europe, Asia, Africa, and Oceania. H. armigera is highly polyphagous, damaging a wide range of natural and cultivated hosts, and achieving major pest status in a number of crops including cotton, tobacco, maize, sorghum, sunflower, soybeans, lucerne, pepper, and tomato. H. armigera pupation occurs at a depth of 1-10 cm in the soil. After larval development, the caterpillar constructs an emergence tunnel from just below the soil surface down to the pupal cell, an enlarged silk chamber in which pupation takes place (Titmarsh et al., 1991). This soil-pupation behavior is characteristic of all Helicoverpa species and more widely in the Heliothinae subfamily (Cayrol, 1972), and consequently it is the only one taken into account in ecological and agronomic studies (Slosser et al., 1975; Caron et al., 1978; Stinner et al., 1979; Eger et al., 1983; Wilson, 1983; Twine and Evans, 1991; Titmarsh et al., 1991; Murray and Wilson, 1991). However, collecting H. armigera larvae on processing tomato crops in the Guadiana River Valley (Vegas del Guadiana, Badajoz, southwestern Spain) in summer 1995 to test insecticide resistance status, an atypical pupation behavior

Pheromone stimulation induces cytoskeletal changes in olfactory dendrites of male silkmoths (Lepidoptera, Saturniidae, Bombycidae)

Abstract: selection. Finally, the question remains as to I. io larvae do not move downwards to the ground but prefer upper spheres and mainly light environments for their pupation? As their pupae have no covering, they risk being detected by small mammals and birds when pupating near or on the ground. On the other hand, pupation in a bright environment and, for example, close to walls and buildings may improve microclimate and shorten pupal development to yield first adults of this year to an earlier time. This should increase the period for a second generation to enable in late summer the development of adults which hibernate. Probably/ . io is a species occurring primarily in humid forests (especially floodplain forests). Their clearings and the margin of a river are the first locations of the stinging nettle [19], which is the only host plant of larvae. Therefore pupation sites in upper spheres and mainly distant to the nettle may offer protection against soil wetness and even the danger of being flooded by the water of the adjacent river. However, all advantages of these pupation sites demands and effective, hormonally controlled cuticular color adaptation by pupae to be concealed from visual hunting predators, for example, birds, which is excellently realized by / . io.

Aliesterase Isozymes and Insecticide Susceptibility in Rice-Feeding and Water-Oat-Feeding Strains of the Rice Stem Borer, Chilo suppressalis WALKER (Lepidoptera: Pyralidae)

Abstract: in the laboratory host prcfercncc tcst KoiKE et al. (1981) also rttported that reciprocal crosses between the two strains resulted in fertile Fl progeny, and interhybrid (Fe × FO crosses also resulted in fertilc F? pregeny. Bascd on thcsc results, KomE et aL {1981) concluded that there is no reproductive isolation between the two strains of the rice stem berer. On the other hand, TANttKA et al. {1981 a, 1982 a) reported that thcre was a significaiit diffi]rcncc in insecticidc susceptibility between thc two strains of thc rice stcrn borer. That is, although the collccting sites

Temperature-Dependent Development of Meteorus communis (Hymenoptera: Braconidae), a Parasitoid of the Variegated Cutworm (Lepidoptera: Noctuidae)

Abstract: Development of a parasitoid, Meteorus communis (Cresson), was compared at 8 constant temperatures, while reared on a noctuid host, the variegated cutworm, Peridroma saucia (Hubner), fed a standard artificial diet. Development from oviposition to adult emergence ranged from 15.7 d at 28°C to 61.8 d at 14°C. The temperature requirement for development from egg to exit of the parasitoid larva (3rd instar) from the host was 143± 9.9 DD above a developmental threshold of 10.3 ± 0.6°C. Development from the 3rd instar to adult emergence required 132 ± 5.4 DD above a developmental threshold of 8.3 ± 0.4°C. Overall, development from egg deposition to adult emergence required 274 ± 14.5DD above a developmental threshold of 9.5 ± 0.5°C. The development of M. communis was compared with 3 populations of P. saucia for 3 temperatures.