Larval Head Capsule Width Research Articles

Effects of maternal body mass, age and crowding on offspring diapause induction and life-history traits in Monochamus alternatus alternatus (Coleoptera: Cerambycidae)

ABSTRACT Monochamus alternatus alternatus is a vector of pine wilt disease and has facultative diapause at the final larval instar. To determine the maternal effect on diapause and life-history traits of offspring, two sorts of rearing experiments were implemented. Two experiments indicated that the body mass of females did not affect the induction of offspring diapause and the heritability of adult body mass did not differ from zero. In another experiment, adults that underwent diapause at three crowding levels of 1, 2 and 4 larvae/pine bolt were allowed to oviposit during their lifetime. Newly hatched larvae were inoculated singly on Pinus thunbergii bolts. Development time from larval inoculation to adult emergence and adult body mass of diapause-forgoing offspring were not affected by larval crowding level in the maternal generation, maternal age, bark surface area of the bolt (a proxy for amount of food available) or offspring sex. Body mass and head capsule width of larvae in diapause decreased with the maternal age but increased with the bark surface area. However, there was no effect of crowding level in the maternal generation. In conclusion, this study found no maternal effects on the induction of offspring diapause, although the influence of maternal photoperiodic and temperature conditions remains to be determined.

Influence of short-term, water-deprived bermudagrass on Orius insidiosus predation and Spodoptera frugiperda larval survival and development

ABSTRACT Turfgrass is susceptible to changes in water availability, and its effects could cascade through multiple trophic levels. In some years, turfgrass is exposed to short drought spells. It is unclear if this short period of water deprivation would cascade to predator performance on herbivory on bermudagrass. Thus, the objective of this study was to determine the effects of water deprivation on predation by Orius insidiosus (Say) (Hemiptera: Anthocoridae) on Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) when mediated by drought-tolerant ‘TifTuf’ and drought-susceptible ‘Tifway’ bermudagrass. Neonates of S. frugiperda and adults of O. insidiosus were caged on bermudagrass in greenhouse conditions. Treatments were three factors: 1) water deprivation at three levels – fully, moderately, and sparsely watered; 2) predator at two levels – present or absent; and 3) bermudagrass at two levels – drought tolerant and susceptible cultivars. The survival of S. frugiperda larvae was reduced when O. insidiosus adults were present regardless of water deprivation levels and bermudagrass cultivars. Reduced larval weight, body length, and head capsule width of S. frugiperda larvae were observed with predators compared to without predators. S. frugiperda larval mortality was significantly greater with predator’s absence for the sparsely-watered treatment than for the fully and moderately-watered treatments. The levels of water deprivation had a partial impact on the survival of S. frugiperda larvae, whereas bermudagrass cultivars did not affect the survival and development of S. frugiperda larvae. Thus, during at least short-term dry spells, O. insidiosus predation can potentially reduce the S. frugiperda population on bermudagrass.

Morphometrics of <i>Spodoptera frugiperda</i> (J E Smith) as Influenced by Cereal Hosts

This laboratory study evaluate the morphometrics of fall army worm Spodoptera frugiperda (J E Smith) influenced by four cereal host plants. In maize, larval head capsule width was 0.22, 0.42, 0.71, 1.13, 1.29 and 2.94 mm for I to VI instars, respectively in sorghum was 0.20, 0.41, 0.67, 1.06, 1.24 and 3.05 mm for I to VI instars, respectively. In pearl millet, larval head capsule width was 0.19, 0.29, 0.52, 0.83, 1.23 and 2.80 mm, for I to VI instars, respectively. In sugarcane, head capsule width was 0.22, 0.43, 0.67, 0.94, 1.22 and 2.70 mm for I to VI instars, respectively. The mean pupal length varied significantly when reared on different cereal host plants, it was significantly maximum on maize (15.10 mm) followed by sorghum (14.20 mm), sugarcane (13.10) and lowest on pearl millet (12.30 mm). The significantly maximum pupal weight was noticed on maize (185.90 mg) followed by sorghum (144.40 mg), sugarcane (124.80 mg) and lowest on pearl millet (104.70 mg).

Morphometrics of <i>Pectinophora gossypiella</i> (Saunders) on Cotton as Influenced by Temperature

The morphometry of life stages of the pink boll worm Pectinophora gossypiella (Saunders) was evaluated at four temperature levels of 20, 25, 30 and 35°C to assess the impact of temperature. Measurement of larval head capsule width, body length, body width and weight on cotton at 20°C were 0.68, 0.87, 0.98 and 1.24 mm, 2.27, 5.80, 7.46 and 10.60 mm, 1.08, 1.58, 1.68 and 2.53 mm and 0.40, 2.84, 24.42 and 64.21 mg for I, II, III and IV larval instars, respectively. The mean pupal length and weight of male and female varied significantly when reared at different temperature levels.

The number of larval instars in the flax weevil (Anagotus fairburni) (Coleoptera: Curculionidae)

ABSTRACT The flax weevil Anagotus fairburni is a large flightless beetle, that is one of the members of the endemic insect ‘megafauna’ of New Zealand. It is a protected species that currently persists only on predator-free islands or in remote and difficult to access alpine areas. Little is documented about the ecology of the flax weevil. In this study we estimated the number of instars in the A. fairburni life cycle by measuring the head capsule widths of larvae collected in the field on Mana Island Scientific Reserve. We used kernel density function estimates to predict average head-capsule widths and the number of larval instars. We then used Brooks-Dyar’s law on the head capsule width data and analysed Brooks and Crosby indexes to refine the estimated number of instars based on imperfect data. Results from sampling of 86 larvae suggested four instar groupings, but further analysis based on Brooks-Dyar’s law found that A. fairburni likely passes through 6 or 7 larval stages prior to pupation, with some uncertainty for smaller instars. Our method provides new data on ecology of an endemic species and provides a framework for further work on similar endangered species where data is imperfect or difficult to gather.

Morphometric traits of Dorcus parallelipipedus (Coleoptera: Lucanidae) larvae and adults: can differences between populations be ruled out?

Summary Stag beetles are saproxylic insects that live in deadwood colonised by fungi and other microorganisms. Due to the cryptic habits of these species, little is known on their biological aspects, especially for the immature stage. In this study, we investigated morphometric traits of lesser stag beetle, Dorcus parallelipipedus (Linnaeus, 1758) (Coleoptera: Lucanidae) larvae and adults, with comparisons between populations. Instar identification by measuring larval head capsule was performed, and the relationship between larval body mass and head capsule width was investigated for each surveyed population. To assess the differences among populations, the scaling relationships for adults between their body and mandibles length was also considered, especially for adult males. Morphometric relationships were described by exponential equations. Differences between populations were sometimes limited to one or the other feature, and particularly ascribed to the larval body mass. These differences could be imputed to several factors, among with those of environmental or genetic order. The scaling relationship of lesser stag beetle adult males showed a positive allometry but did not differ among populations, indicating that morphological traits within a species and sex may be biologically retained. Findings are discussed from the perspective of D. parallelipipedus life history.

Biological parameters and comparative morphometrics studies of Scirpophaga spp. in rice

The comparative biological studies on yellow stem borer, Scirpophaga incertulas (Wlk.) and white Stem Borer, Scirpophaga fusciflua Hampson showed that the moths of both species preferred to lay eggs on the dorsal surface of leaves. The eggs were laid in masses during night hours and covered with brownish hairs of the anal tuft. The maximum eggs of S. incertulas hatched on 6th day, whereas the S. fusciflua eggs hatched on the 5th day with per cent hatchability of 86 and 93 per cent, respectively. There were six larval instars in S. incertulas with 25-34 days larval duration and five for S. fusciflua with 26-31 days larval duration. The pupal period lasts for 7-9 days in both species, and the adults emerge from the pupae during dusk hours. Adults exhibited sexual dimorphism. The longevity of male and female moths was also similar in both species. The morphometries of larval head capsule width were more in S. incertulas as compared to S. fusciflua. Male pupal weight of both the species were almost similar but it was varied significantly in female pupa S. incertulas (0.024mg) and S. fusciflua (0.032mg).

Improved Random Forest for the Automatic Identification of Spodoptera frugiperda Larval Instar Stages

Spodoptera frugiperda (fall armyworm, FAW) is a global agriculture pest. Adults have a strong migratory ability and larvae feed on the host stalks, which pose a serious threat for maize and other crops. Identification and counting of different instar larvae in the fields is important for effective pest management and forecasting emergence and migration time of adults. Usually, the technicians identify the larval instars according to the larva morphological features with the naked eye or stereoscope in the lab. The manual identification method is complex, professional and inefficient. In order to intelligently, quickly and accurately identify the larval instar, we design a portable image acquisition device using a mobile phone with a macro lens and collect 1st-6th instar larval images. The YOLOv4 detection method and improved MRES-UNet++ segmentation methods are used to locate the larvae and segment the background. The larval length and head capsule width are automatically measured by some graphics algorithms, and the larval image features are extracted by SIFT descriptors. The random forest model improved by Boruta feature selection and grid search method is used to identify the larval instars of FAWs. The test results show that high-definition images can be easily collected by using the portable device (Shenzhen, China). The MRES-UNet++ segmentation method can accurately segment the larvae from the background. The average measurement error of the head capsule width and body length of moth larvae is less than 5%, and the overall identification accuracy of 1st–6th instar larvae reached 92.22%. Our method provides a convenient, intelligent and accurate tool for technicians to identify the larval instars of FAWs.

Biology and Nutritional Indices of the Fall Army Worm <i>Spodoptera Frugiperda</i> (J E Smith) on Maize

Lifecycle, progressive growth of larval head capsule, and nutritional indices of Spodoptera frugiperda (J E Smith) on maize (Co-H6) were studied at the Department of Agricultural Entomology, TNAU, Coimbatore during 2018-19. Incubation, total larval, and pupal periods were observed as 2-3, 13-20, and 7-11 days, respectively. The total lifecycle of male and female was 33-46 and 35-47, respectively. The head width was observed to be 0.34, 0.60, 0.89, 1.32, 1.86, and 2.36 mm from the first to the sixth instars, respectively. Linear regression analysis showed a significant relationship between larval instars and head capsule width (R2=0.0979); and geometric progression ratio was observed as 1.48. Nutritional indices were also studied for the third and fifth instar on the maize plants. Consumption index (CI) and approximate digestibility (AD) increased with larval age, while efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were inversely related to age. These values for the third and fifth instar were- CI= 2.30 and 2.31; AD=35.7 and 40.29; ECI=18.33 and 12.21; ECD=51.33 and 30.3, respectively.

Biomorphic Characters of Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) on Maize in Pakistan

Fall armyworm, Spodoptera frugiperda belongs to order Lepidoptera and family Noctuidae, is becoming a serious threat in maize growing areas of the world. Firstly, it was reported from African countries and caused significant economic crop losses. Recently the pest has been reported from various areas of Pakistan and knowledge of biomorphic characters was important. By keeping in view, the current study was conducted. The study resulted that complete metamorphosis was observed. The eggs were white to yellow in colour and dome in shape with 2-3 days of the incubation period. The egg width and thickness were recorded as 0.22 and 0.19 mm, respectively. Six larval instars were recorded. The pinacula of each seta was well recorded on all larval instar but more conspicuous in the last instar (6th) as compared to others. Inverted Y line was present on larvae head that mostly differentiates this species from other reported Spodoptera species. First, second, third, fourth, fifth and sixth larval head capsule width was 0.18±0.02, 0.29±0.00, 0.50±0.01, 0.76±0.47, 1.10±0.13 and 1.98±0.12 mm, respectively. The length and width of the 6th instar larva were 26.98±2.93 and 3.90±0.00 mm, respectively. The total larval period was 15-20 days on maize leaves. Obtect pupa was whitish green. Male was short-lived than female. The pre oviposition, oviposition and post oviposition periods were 2-5, 2-4 and 4-6 days, respectively. The study will be proved fruitful for coming researchers and farmers to control this pest.

Unexpected larval habit of Listronotus bonariensis (Coleoptera: Curculionidae) raises questions about population dynamics analysis and management

AbstractListronotus bonariensis (Kuschel) is a pest of agriculturally important graminaceous species, with mining larvae that kill the stems of the host plants. In this study, larval populations were measured in spring and summer in irrigated dairy grassland comprising Lolium perenne L. (cv. Nui) with and without the endophyte Epichloë festucae var. lolii Latch, M.J. Chr. and Samuels and Poa annua L.. Larvae were extracted from tillers taken from the swards of these two grass species and extracted from turves, and L. bonariensis population densities were estimated from tiller and turf larval counts on a m−2 basis. Over the study period, the total number of larvae and larval densities extracted from turves was on average 2× greater than indicated from tillers. In most seasons, larval densities from turves were significantly higher than those from the tillers, though there was no correlation between tiller and turf larval densities. Mean head capsule widths of larvae emerging from turf samples showed significant seasonal effects compared with tillers, while mean head capsule widths of all four instars were significantly greater when extracted from tillers compared with turves. There was a significant endophyte effect on head capsule widths of larvae collected in summer, but the effect was not consistent across instars or source. Conversely, no significant endophyte effect on head capsule width was found in spring populations from either tillers or turves. This study shows that in irrigated dairy pasture, a high proportion of L. bonariensis larvae can live externally of tillers, presumably among the organic matter around the base of grasses in irrigated dairy pasture, and that density estimates based only on tiller populations will have significantly underestimated actual numbers. Having a precise indication of larval population densities is essential when developing life tables or determining economic damage threshold levels.

Biometric studies of <em>Corcyra cephalonica</em> (Stainton) at different temperature levels

The observed progression factors for larval head capsule width, body length, body width and body weight at 20 0C temperature were 1.05, 1.25, 0.97, and 1.32, respectively. The corresponding values at 25 0C, 30 0C and 35 0C temperature were (1.16, 1.40, 0.99 and 1.38), (1.23, 1.38, 0.99, and 1.37) and (1.16, 1.25, 0.99 and 1.48), respectively.

Effects of Cd, Zn or Pb stress in Populus alba berolinensis on the development and reproduction of Lymantria dispar.

In order to investigate the effects of heavy metal stress on woody plant defense against phytophagous insects, we studied development and reproduction traits of the gypsy moth, Lymantria dispar that were separately fed with leaves plucked from poplar seedlings (Populus alba berolinensis) grown in either non-contaminated soil (control), Cd-contaminated soil (1.5 mg/kg), Zn-contaminated soil (500 mg/kg) or Pb-contaminated soil (500 mg/kg). The results showed that feeding on Cd or Pb stressed poplar leaves significantly decreased L. dispar larval weights, body lengths and head capsule widths, pupal weights and female fecundity, and delayed the duration of larval development. Similar effects from the Zn stressed poplar leaves were also observed on all the above mentioned variables except male pupal weight and larval development duration that showed no differences from the control. Cd, Zn, or Pb stressed poplar leaves had no significant effects on L. dispar larval survival, pupation and emergence rates; in fact, both larval survival and pupation rates reached 100%. These results suggest that Cd, Zn or Pb stress in P. alba berolinensis might help the trees defend against the defoliator, however; L. dispar may in turn have an effective detoxification mechanism for lessening the effects of plant-mediated defenses and heavy metals in leaves on larval survival, pupation and eclosion.

Determination of Helicoverpa armigera (Lepidoptera: Noctuidae) larval instars and age based on head capsule width and larval weight

Larνae of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) were reared in laboratory conditions (26°C, 16:8 L:D) and measurements of larval head capsule width, and body weight, were used in order to determine the boundaries of larval instars. Larvae of Η. armigera completed development in 5 to 7 instars. Head capsule width could predict the larval instar only for Ll. The upper boundary of head width for L1 was 0.4mm. Body weight could predict both L1 and L2 larval instars. Boundaries between L1-L2 instars were found to be 1 mg and for L2-L3 5,5 mg. Correlation and regression analysis suggest that a combination of head capsule width and body weight can predict both larval instars and chronological age under constant conditions in the laboratory.

Host Selection, Growth, and Survival of Melonworm (Lepidoptera: Crambidae) on Four Cucurbit Crops Under Laboratory Conditions.

The melonworm, Diaphania hyalinata L. (Lepidoptera: Crambidae), is one of the most serious insect problems affecting cucurbit production. We evaluated the relative preference and suitability of yellow squash, zucchini, cucumber, and watermelon to melonworm by measuring its oviposition, larval feeding preference, survivorship, and developmental responses in the laboratory. Whole plants were used for oviposition study, whereas host leaf discs were used for all the other studies. Watermelon feeding resulted in the longest larval development period (14.3 d), greatest prepupal weights and survivals rates (92%; first instar to adult) among the four crops. However, for watermelon, adult oviposition preference (199.5 eggs/♀), egg survival (70%), and larval feeding (4.1% defoliation) were numerically or statistically lowest, and larval head capsule widths and whole-body lengths were smallest. When differences occurred among these variables, yellow squash, zucchini, and cucumber were each typically higher (or quicker to develop) than watermelon. So why do melonworm adults not prefer watermelon, or at least select it as frequently as squash and cucumber when ovipositing? The answer likely is that there might be some variation in the important chemical components among these cucurbits. We suggest that comparison of kairomones and allomones from watermelon and related cucurbits would be very useful for determining the combination resulting in the lowest risk of damage to the more susceptible cucurbits (assuming the levels can be modified without seriously affecting the crops).

The Nutritional Ecology ofDectes texanus(Coleoptera: Cerambycidae): Does Host Choice Affect the Macronutrient Levels in Overwintering Larvae?

Abstract Dectes texanus LeConte (Coleoptera: Cerambycidae) is a stem-boring cerambycid that is an agricultural pest of soybean and cultivated sunflower. For D. texanus, cultivated sunflower is thought to be nutritionally superior to soybean and preferred over soybean. This study compared the macronutrient levels in overwintering larvae and the pith of the host plants to determine if soybean is an inferior host. The levels of total protein, total carbohydrates, and total lipids were measured in larvae from sunflower and soybean; larval head capsule width and larval mass also were compared. There were no differences between levels of total protein and total carbohydrates per unit mass between larvae from the 2 hosts; however, larvae from sunflower had significantly higher levels of lipids than larvae from soybean. A comparison of head capsule width indicated that larvae from soybean had significantly larger head capsule widths than those from sunflower, suggesting that soybean-fed larvae were larger or were...

EVALUATION OF SUBLETHAL EFFECTS OF Ipomoea cairica LINN. EXTRACT ON LIFE HISTORY TRAITS OF DENGUE VECTORS

Plant derived insecticides have considerable potential for mosquito control because these products are safer than conventional insecticides. This study aimed to investigate sublethal activities of Ipomoea carica or railway creeper crude acethonilic extract against life history trait of dengue vectors, Aedes albopictus and Aedes aegypti. The late third instar larvae of Ae. albopictus and Ae. aegypti were exposed to a sublethal dose at LC50 and larvae that survived were further cultured. Overall, Ipomea cairica crude extracts affected the whole life history of both Aedes species. The study demonstrated significantly lower egg production (fecundity) and eggs hatchability (fertility) in Ae. albopictus. The sublethal dose of crude extracts reduced significantly the width of larval head capsule and the wing length of both sexes in both Aedes species. The significance of sublethal effects of I. cairica against Aedes mosquitoes was an additional hallmark to demonstrate further activity of this plant despite its direct toxicity to the larvae. The reduced reproductive capacity as well as morphological and physiological anomalies are some of the effects that make I. cairica a potential candidate to be used as a new plant-based insecticide to control dengue vectors.

Development and Life History ofSitophilus zeamais(Coleoptera: Curculionidae) on Cereal Crops

The maize weevil,Sitophilus zeamaisMotschulsky (Coleoptera: Curculionidae), is one of the most destructive pests of stored cereals. Knowledge of the life history and biology is important to the development of an integrated pest management program. Investigation was carried out on developmental biology ofS. zeamaison four main cereal crops, maize, rice, sorghum, and millet, under laboratory conditions. Egg incubation, oviposition periods, and larval instar development were not different significantly among the food hosts. Number of eggs laid varied significantly among the cereal grains; mean fecundity was highest on maize (67.2±3.16) and lowest on millet (53.8±0.17). Number of immature (larva and pupa) and adult stages varied significantly among the cereal grains. There exist four larval instars with a varied mean head capsule width, with a mean total instar larval developmental period of 23.1, 22.2, 22.2, and 21.6 d on maize, rice, sorghum, and millet, respectively. There was linear relationship and significant correlation between the stages of larval development and head capsule width. The mean developmental period from egg to adult varied, being highest on maize (34.7 d) and lowest on sorghum (33.5 d).

Tolerance of eCry3.1Ab in Reciprocal Cross Offspring of eCry3.1Ab-Selected and Control Colonies of Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae).

Two new insect colonies were created by separating virgin western corn rootworm, Diabrotica virgifera virgifera LeConte, males and females from both a selected laboratory colony that was being reared on eCry3.1Ab-expressing corn (Zea mays L.) and a control colony reared on its near-isoline corn. Females from the selected colony were paired with males of the control colony and vice versa to create both a selected female by control male colony (Sel♀) and control female by selected male colony (Con♀). Both colonies along with their parental colonies (eCry3.1Ab-selected and control) were evaluated on eCry3.1Ab-expressing corn and its near-isoline in seedling assays. Larvae from each colony were also used in diet toxicity experiments in order to determine the LC50 and EC50 values for the eCry3.1Ab toxin for each. Statistical analysis of seedling assay experiments did not indicate any significant colony×corn interaction but did show a significant main effect of corn type for both larval recovery and larval head capsule widths. Results from the diet toxicity assays showed the control colony to have a significantly lower LC50 value than the selected and cross colonies and a significantly lower EC50 than the selected and Con♀ colonies. Calculations of dominance values (h) of eCry3.1Ab resistance traits from seedling assays indicated that the two reciprocal cross colonies have a dominance value (h) of ∼1, suggesting dominance of the eCry3.1Ab resistance trait.

Life History of the Tamarind Weevil, Sitophilus linearis (Herbst) (Coleoptera: Curculionidae), on Tamarind Seed

The tamarind weevil, Sitophilus linearis Herbst (Coleoptera: Curculionidae), is an important pest of tamarind and other Caesalpinioideae. Investigating its life history is important in the implementation of management strategy. Its life history was monitored daily to understand its developmental biology on tamarind seed following standard procedures under laboratory conditions of 24–30°C temperature, 60–70% relative humidity, and 12L : 12D photoperiod. The egg incubation period lasted 3.17 ± 0.07 days. A mated female of S. linearis laid an average of 165 ± 5.78 eggs during an oviposition period of 86.8 ± 2.47 days. There were four larval instars, with a total larval developmental period of 16 days. The pupal period lasted 8 days, and adult lived 108.5 ± 3.61 days. The overall growth ratio for the four instars was 1.33. There was a regular relationship and significant correlation (r=0.94) between the stages of larval development and head capsule width.