Seventh Instar Research Articles

Food preference of the Calliteara cerigoides Walker on several species of Shorea sp. leaves

Shorea sp. (meranti) is a wood-producing tree from Indonesia that has many benefits in world trade. Meranti cultivation is carried out to rehabilitate and develop plantation forests. However, meranti cultivation is susceptible to various pest attacks, including Calliteara cerigoides. This study aimed to determine the food preferences of C. cerigoides and to analyze the phytochemical compounds in meranti leaves. Pest food preferences were tested by testing three meranti leaf species on C. cerigoides larvae. Three species of meranti were Shorea selanica, S. pinanga, and Shorea sp. Phytochemical tests were carried out by identifying seven secondary metabolic compounds in meranti leaves. The results showed that C. cerigoides larvae preferred S. selanica leaves and survived until the seventh instar. The content of tannin and hydroquinone phenolic compounds in the leaves of S. pinanga is thought to be an obstacle in the pest’s food preference, causing the larvae to die in the third instar. The content of alkaloid and flavonoid compounds in the leaves of Shorea sp. was suspected to be the cause of the larvae not surviving until the instar phase and only until the fourth instar. Morphological factors and the content of chemical compounds in meranti leaves affect the eating preferences of larvae.

Ontogenetic trajectories in Callinectes danae (Crustacea: Brachyura): sex and age polymorphism

We analysed the morphological variations through geometric morphometric approaches of the dorsal and ventral views of growing male and female Callinectes danae Smith 1869, based on the hypothesis that swimming crabs present polymorphism during growth. Our research identified six instars for females, seven instars for males and one instar for unsexed individuals (young). The sixth instar of females and the seventh instar of males were composed of adults. We identified 20 landmarks from the dorsal view, and 16 landmarks from the ventral view. Based on canonical analysis and Procrustes distance, we observed the formation of clearly separated instars (both views), indicating a significant change during ontogeny, not only in the pubertal moult. The most prevalent changes occurred in the abdomen, with males thinning and females broadening the abdomen during growth. In the dorsal view, we observed a displacement of anterolateral spines to the posterior region throughout the growth period and that the anterolateral and frontal teeth of juveniles were more ornate than those of adults. The ontogenetic trajectories for males and females have similar origins and follow different directions over the instars, with maximum distance after the pubertal moult (P < 0.05).

Biological and Immune Response of <I>Galleria mellonella</I> (Lepidoptera: Pyralidae) to Sodium Tetraborate

Inorganic insecticides are commonly used in urban pest management because of their low mammalian toxicity. We tested the effects of sodium tetraborate (ST) on life parameters of greater wax moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae), to determine its sublethal toxicity on the insect. Survival, development, adult longevity, and fecundity of the wax moth were investigated by rearing larvae on artificial diets containing ST at concentrations of 0.005, 0.1, 0.2, or 0.3%. Larvae reared on medium at the highest concentration of ST (0.3%) had significantly decreased survival to the seventh instar and prolonged time required to reach the seventh instar. This concentration reduced pupa and adult yields to 12.5%, and it also prolonged development by 5 d. ST did not significantly influence adult longevity. Dietary ST led to significant decreases in fecundity and egg viability. Oviposition of survivors at the highest ST concentration (0.3%) was completely inhibited. Lysozyme content was decreased in larval hemolymph and fat body at high dietary ST concentrations. Fat body lysozyme content was significantly increased two-fold for larvae reared on diet at the lowest concentration of ST (0.005%). However, the highest concentration (0.3%) dramatically decreased fat body lysozyme content from 0.12 +/- 0.013 to 0.006 +/- 0.003 mg/ml in seventh instars. We infer that sublethal levels of dietary ST substantially influence life history parameters and immunocompetence in G. mellonella.

Penicillin-Induced Oxidative Stress: Effects on Antioxidative Response of Midgut Tissues in Instars of <I>Galleria mellonella</I>

Penicillin and other antibiotics are routinely incorporated in insect culture media. Although culturing insects in the presence of antibiotics is a decades-old practice, antibiotics can exert deleterious influences on insects. In this article, we test the hypothesis that one of the effects of dietary penicillin is to increase oxidative stress on insects. The effects of penicillin on midgut concentrations of the oxidative stress indicator malondialdehyde (MDA) and on midgut antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase [GST], and glutathione peroxidase [GPx]) and transaminases (alanine aminotransferase and aspartate aminotransferase) activities in greater wax moth, Galleria mellonella (L.), were investigated. The insects were reared from first instars on artificial diets containing 0.001, 0.01, 0.1, or 1.0 g penicillin per 100 g of diets. MDA content was significantly increased in the midgut tissues of each larval instar reared in the presence of high penicillin concentrations. Activities of antioxidant and transaminase enzymes did not show a consistent pattern with respect to penicillin concentrations in diet or age of larvae. Despite the increased penicillin-induced oxidative stress in gut tissue, antioxidant and transaminase enzymes did not correlate with oxidative stress level or between each other in larvae of other age stages except for the seventh instar. We found a significant negative correlation of MDA content with SOD and GST activities in seventh instars. SOD activity was also negatively correlated with CAT activity in seventh instars. These results suggest that exposure to dietary penicillin resulted in impaired enzymatic antioxidant defense capacity and metabolic functions in wax moth larval midgut tissues and that the resulting oxidative stress impacts midgut digestive physiology.

Penicillin-Induced Oxidative Stress: Effects on Antioxidative Response of Midgut Tissues in Instars of Galleria mellonella

Penicillin and other antibiotics are routinely incorporated in insect culture media. Although culturing insects in the presence of antibiotics is a decades-old practice, antibiotics can exert deleterious influences on insects. In this article, we test the hypothesis that one of the effects of dietary penicillin is to increase oxidative stress on insects. The effects of penicillin on midgut concentrations of the oxidative stress indicator malondialdehyde (MDA) and on midgut antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase [GST], and glutathione peroxidase [GPx]) and transaminases (alanine aminotransferase and aspartate aminotransferase) activities in greater wax moth, Galleria mellonella (L.), were investigated. The insects were reared from first instars on artificial diets containing 0.001, 0.01, 0.1, or 1.0 g penicillin per 100 g of diets. MDA content was significantly increased in the midgut tissues of each larval instar reared in the presence of high penicillin concentrations. Activities of antioxidant and transaminase enzymes did not show a consistent pattern with respect to penicillin concentrations in diet or age of larvae. Despite the increased penicillin-induced oxidative stress in gut tissue, antioxidant and transaminase enzymes did not correlate with oxidative stress level or between each other in larvae of other age stages except for the seventh instar. We found a significant negative correlation of MDA content with SOD and GST activities in seventh instars. SOD activity was also negatively correlated with CAT activity in seventh instars. These results suggest that exposure to dietary penicillin resulted in impaired enzymatic antioxidant defense capacity and metabolic functions in wax moth larval midgut tissues and that the resulting oxidative stress impacts midgut digestive physiology.

ASPECTS OF THE GROWTH AND REPRODUCTION OF THE CORAL GALL CRAB HAPALOCARCINUS MARSUPIALIS

Abstract Growth and reproduction were studied in the coral gall crab Hapalocarcinus marsupialis from fringing reefs in the Egyptian Red Sea. The host coral was Stylophora pistillata. The galls were divided into five stages, and the later stages contained larger crabs and a higher proportion of ovigerous females. Female crabs ranged from 1.17 to 5.33 mm in carapace width. They matured at about 2.5-mm carapace width (probably in the fourth instar); maturity was indicated by an increase in abdomen size, ripening ovaries, mating, and egg laying. The largest females were probably in the seventh instar. After maturity females survived for some 10 months and were ovigerous for 80% of that time, producing eight or more broods. These were all fertilised from the original mating. Reproductive investment was high, both per brood and per year.

Consumo foliar de cultivares de arroz irrigado por Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

O consumo médio de área foliar da lagarta-da-folha Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), em função do sexo e do ínstar, foi determinado em condições de laboratório em folhas de arroz, das cultivares BR-IRGA 410 e Embrapa 6-CHUÍ. Não houve diferença significativa no consumo total de área foliar das duas cultivares pelas lagartas que resultaram em machos e fêmeas. Ocorreram diferenças significativas entre ínstares, sendo o maior consumo constatado no 7º ínstar. A duração do estágio larval não diferiu para machos e fêmeas nas duas cultivares, entretanto houve diferença significativa na duração dos ínstares, independente do sexo. O 7º ínstar foi o mais longo, onde concentrou-se o maior consumo foliar diário. No consumo médio diário foram observados valores muito próximos tanto para machos como para fêmeas dentro dos cinco ínstares analisados nas duas cultivares testadas, constatando-se um aumento considerável a partir do 5º ínstar.

Leaf quality and insect herbivory in model tropical plant communities after long-term exposure to elevated atmospheric CO2.

Results from laboratory feeding experiments have shown that elevated atmospheric carbon dioxide can affect interactions between plants and insect herbivores, primarily through changes in leaf nutritional quality occurring at elevated CO2. Very few data are available on insect herbivory in plant communities where insects can choose among species and positions in the canopy in which to feed. Our objectives were to determine the extent to which CO2-induced changes in plant communities and leaf nutritional quality may affect herbivory at the level of the entire canopy. We introduced equivalent populations of fourth instar Spodoptera eridania, a lepidopteran generalist, to complex model ecosystems containing seven species of moist tropical plants maintained under low mineral nutrient supply. Larvae were allowed to feed freely for 14 days, by which time they had reached the seventh instar. Prior to larval introductions, plant communities had been continuously exposed to either 340 μl CO2 l-1 or to 610 μl CO2 l-1 for 1.5 years. No major shifts in leaf nutritional quality [concentrations of N, total non-structural carbohydrates (TNC), sugar, and starch; ratios of: C/N, TNC/N, sugar/N, starch/N; leaf toughness] were observed between CO2 treatments for any of the species. Furthermore, no correlations were observed between these measures of leaf quality and leaf biomass consumption. Total leaf area and biomass of all plant communities were similar when caterpillars were introduced. However, leaf biomass of some species was slightly greater-and for other species slightly less (e.g. Cecropia peltata)-in communities exposed to elevated CO2. Larvae showed the strongest preference for C. peltata leaves, the plant species that was least abundant in all communites, and fed relatively little on plants species which were more abundant. Thus, our results indicate that leaf tissue quality, as described by these parameters, is not necessarily affected by elevated CO2 under relatively low nutrient conditions. Hence, the potential importance of CO2-induced shifts in leaf nutritional quality, as determinants of herbivory, may be overestimated for many plant communities growing on nutrient-poor sites if estimates are based on traditional laboratory feeding studies. Finally, slight shifts in the abundance of leaf tissue of various species occurring under elevated CO2 will probably not significantly affect herbivory by generalist insects. However, generalist insect herbivores appear to become more dependent on less-preferred plant species in cases where elevated CO2 results in reduced availability of leaves of a favoured plant species, and this greater dependency may eventually affect insect populations adversely.

Induction of ultranumerary larval ecdyses by ecdysone does not require and active prothoracic gland in the silkworm, Bombyx mori

When larvae of Bombyx mori were reared on an artificial diet supplemented with ecdysone, they ecdysed to the seventh instar. Their prothoracic gland was inactive in all instars, when tested in vitro. By contrast, when larvae were reared on a diet supplemented with 20-hydroxyecdysone, they ecdysed to the fifth instar and all of them died. The prothoracic gland of larvae fed 20-hydroxyecdysone was active during the fourth instar and ecdysone was found in the hemolymph, but during the fifth instar, gland activity greatly diminished and little ecdysone was detected in the hemolymph. We propose that an active prothoracic gland is not required for the induction of “ultranumrary larval ecdyses” by ecdysone and that ecdysone, or its metabolites other than 20-hydroxyecdysone, has a critical role in the molting process.

Temporal polyethism in incipient colonies of the primitive termiteZootermopsis angusticollis: A single multiage caste

Division of labor was studied in incipient colonies of the dampwood termite Zootermopsis angusticollisby recording repertoire size, behavior frequencies, and time budgets of larvae. Behavioral repertoire size increased with age: first- and secondinstar larvae were mainly inactive, whereas larvae of the third through seventh instars performed 64–100% of all tasks. The increase in repertoire size from the second to the third instar was abrupt; repertoire size and composition remained more or less constant for older instars. No correlation between age (instars III–VII) and tasks was identified, suggesting that colony labor is performed by a single functional caste that spans the third to the seventh instar without any age-based division of labor. Small colony size, low oviposition rate, simple nest architecture, a lack of spatial association of tasks, and the potential for attaining reproductive status appear to be associated with the lack of age-related behavioral specialization in Z. angusticollis.In effect, the absence of temporal polyethism in this species is likely a consequence of its nesting habits and physiological and developmental constraints.

Simulation-Models for the Phenological Development of Mythimna-Convecta (Walker) (Lepidoptera, Noctuidae)

Larvae of armyworm, Mythimna convecta, were reared under fluctuating temperatures (1-7-degrees; 3-13-degrees; 7-17-degrees; 11-24-degrees; 31-39-degrees-C). Data from these trials were combined with previsouly published data derived from constant-temperature studies (ranging from 15-degrees to 33-degrees-C) to model the effects of temperature on development rate. Temperature-dependent development rates for each of eight immature stages were described by one of three non-linear functions and by a linear model modified to improve the performance about the lower and upper temperature extremes. At the lower and upper thermal limits (< 11-degrees-C and > 33-degrees-C) of the species, survival of larvae under fluctuating temperatures was greater than recorded in previously published studies under equivalent constant temperatures. A serious constraint on fitting a model to the later larval instars was the inconsistent appearance of a seventh instar. The two sets of models were evaluated against field development in three winter and one summer experiments. The modified linear model, with capacity to manipulate predicted development at threshold temperatures, provided a marginally better prediction than did the non-linear model. The sine wave method for estimating diurnal temperatures from minimum and maximum temperatures was shown to produce overestimates of development rates. A correction factor for the seasonal conditions in western Victoria was provided.

Some Aspects of the Developmental Biology of Blaps kollari (Coleoptera: Tenebrionidae) Under Laboratory Conditions

The study focused on the influence of an artificial diet on the health, fecundity, duration and pattern of development, and survival rates of the beetle, Blaps kollari Seidlitz. The breeding period was confined mainly to the cooler months during which females laid their eggs; the largest number per individual was 650. Sixty-two percent of the eggs that matured in 9 d produced viable first-instar larvae. Voracious feeding from second instar onward produced an exponential weight gain; a coefficient of 400 from second to terminal eighth instar. In isolation, instar mortality was small; larvae consumed exuviae when not removed, and communal life allowed considerable cannibalism. Full larval development was quite rapid, lasting only 80 d, and terminated in a prolonged semidormant, nonfeeding pharate-pupal stage; a majority entered this stage after the seventh instar. Last-instar larvae were susceptible to a bacterial infection. Mortality and morbidity increased during pharate-pupal stage and deformity occurred also during pupal and adult molts. About 68% of pharate-pupal to pupal molts were normal. The pupal stadium averaged 15 d, during the latter half of which rudiments of the sternal gland, a characteristic of the males, appeared between sternites two and three. A majority of the pupal-to-adult molts resulted in deformed individuals. Experimental groups allowed cannibalism, and exuvial feeding fared better at this molt. A total of 8.5% healthy normal adults was obtained from all groups taken together. The pharate-pupal and newly emerged adult phases were accompanied by a significant weight loss. Within 1 mo after adult feeding was initiated, weight exceeded the maximum attained by last-instar larvae and plateaued within 2 mo.

Serological characterization of soluble proteins in greater wax moth larval blood

1. 1. The pattern of larval blood proteins of the last seventh instar of the greater wax moth was characterized using polyacrylamide gel electrophoresis under non-denaturating buffer systems and the Ouchterlony double immunodiffusion test. 2. 2. Gel electrophoresis yielded 15 well-defined bands of blood proteins which differ apparently by content, molecular weight and serology. 3. 3. All soluble proteins visualized electrophoretically induced specific antibodies in rabbits which react with respective blood proteins in immunodiffusion. 4. 4. Fifteen proteins of blood form 15 corresponding precipitation arcs.

Effects of wing‐pad removal and corpus allatum implantation on development of wings, flight muscles, and related structures in the striped ground cricket, Allonemobius fasciatus

ABSTRACT. Removal of a hindwing pad from late instar nymphs of the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae) inhibits the formation of long‐winged adults. All nymphs become short‐winged when their hindwing pad is removed during the sixth (penultimate) instar or during the first 2 days of the seventh instar. When a hindwing pad is removed on day 4 of the seventh instar or later, there is no effect on wing development and at least 50% of the crickets emerge as long‐winged adults as in controls.The period sensitive for removal of a hindwing pad varies among different structures, e.g. elytra, hindwings, flight muscles, and the acrotergite of the first abdominal segment. As a result, some intermediate forms are produced when a hindwing pad is removed in the middle of the seventh instar.Implantation of corpora allata (CA) into late instar nymphs also inhibits formation of long‐winged adults. When CA are implanted on day 2 or 3 of the seventh instar, some of the resulting adults have abnormally short elytra. Implantation of CA at an earlier stage produces supernumerary (eighth instar) nymphs.

Effect of host plant on moulting in the African armywormSpodoptera exempta(Walk.) (Lepidoptera: Noctuidae) at constant temperature and humidity conditions

AbstractThere are five caterpillar instars in the life cycle ofSpodoptera exempta(Walk.) when they feed upon star grass,Cynodon dactylon(L.) Pers., maize,Zea maisL. and Kikuyu grass,Pennisetum clandestinumChiov. at 25–30°C. When the temperature is 18°C, however, there was an additional instar in the cycle. Similarly extra instars are formed on Guinea grass,Panicum maximumJacq.,Setaria plicatilis(Hochst.) Hack, and a sedge,Cyperus maranguensisK. Schm. even when the temperature appears to be sufficiently high for normal development. Occasionally the additional sixth instar is also too small to pupate, in which case a seventh instar is formed. It appears that caterpillars on nutritionally inadequate host plants or those at low temperatures are being partially starved and must continue moulting until the appropriate size is attained or exceeded. Measurements of the head capsule widths or distances between the frontal clypeal setae suggest that only individuals reaching or exceeding a species specific threshold size pupate. Extra moults appear to be an adaptation to environmental fluctuations obtaining within the range of occurrence ofS. exempta.

Ultrastructural study of the postembryonic development of the neural lamella of Galleria mellonella L. (Lepidoptera).

The neural lamella encapsulating the brain of the wax moth Galleria mellonella develops from a very thin (80-120 nm) layer in the first larval instar, resembling the basal lamina, to a thick (1-4 micrometer) sheath composed of two zones in the seventh (last) instar. After its breakdown at the time of larval-pupal ecdysis the neural lamella is reconstructed in the pupa, 2-3 days before pupal-adult ecdysis. The cells of the perineurium seem to be responsible for the formation of the neural lamella, both in the larva and pupa, even though its ultrastructure differs at these stages.

THE SEVEN LARVAL INSTARS OF SIMULIUM ARCTICUM (DIPTERA: SIMULIIDAE)

AbstractThe larvae of Simulium arcticum Malloch in three collections from the North Saskatchewan River of May and June 1969, 1971, and 1974 showed seven instars. The first instar larva possessed an egg burster and the seventh instar larva possessed separated cervical sclerites. The intervening instars, however, could be decisively identified only by measuring the lengths of the postgenae. The observed mean postgenal lengths for all but the seventh instar were near those predicted by the regression line logeY = 4.1216 +.2927X. The observed mean lengths of whole larvae of all seven instars were near those predicted by the regression line logeY = −.5234 +.3238X but with relatively large standard deviations. Thus there were geometric increases in size between successive instars.

Développement postembryonnaire des appareils génitaux mâle et femelle de Pamphagus elephas L. (Orthoptera: Acrididae)

In Pamphagus elephas L. male and female reproductive systems appear very early. In the male, rudiments of testicular follicles, genital ducts and accessory structures appear before hatching. Spermatogenesis begins in the third instar but spermiogenesis starts in the seventh. Accessory glands also are formed in the seventh instar. In the female, oogenesis begins in the second instar. Spermatheca and the common oviduct appear during embryological developments.