Determination of critical threshold for induction and termination of diapause (hibernation) are important for better understanding the bio-ecology and population dynamics of Chilo partellus (Swinhoe) under varying climatic conditions. We studied initiation and termination of hibernation under five temperature and photoperiod regimes viz., 27°C + 12L:12D, 22°C + 11.5L:12.5D, 18°C + 11L:13D, 14°C + 10.5L:13.5D and 10°C + 10L:14D under fixed and ramping treatments, and the observations were recorded on various phenological and developmental characteristics at weekly intervals. Present studies revealed that the induction of hibernation in C. partellus larvae takes from 46 to 56 days depending upon temperature and photoperiod conditions. Induction of hibernation varied from 7.9 to 18.3% across treatment conditions, indicating that not all C. partellus larvae undergo diapause under prevailing environmental conditions. Weight, length and head capsule width of diapausing larvae were found significantly lower than the non-diapausing larvae. The non-diapausing C. partellus larvae required a thermal threshold of 1068 degree-days under ambient conditions, while in case of hibernating larvae it varied significantly across treatment conditions. Diapausing larvae underwent up to five supernumerary moults, wherein highest percentage of diapausing larvae (35.7%) exhibited two supernumerary moults. The developmental time of diapausing larvae varied from 94.9 to 160.4 days across treatments. A population loss of 17.2-28.3% was recorded in C. partellus due to hibernation, which has implications for population buildup of post-hibernation first brood and management strategies.

Diapause is an important adaptive trait in certain groups of insects at a particular stage, which contribute in controlling insect ecology, phenology, and physiology. Considering the importance of various factors in appropriate combinations, we studied effects of different temperature and photoperiod conditions on larval morphometrics, development, induction, and termination of estivation, and overall mortality due to estivation in Chilo partellus (Swinhoe). Weight, length, and head capsule width of C. partellus larvae significantly increased with increase in temperature and photoperiod treatments upto certain age and duration of exposure. According to Dyar's ratio, overall head capsule width progressed geometrically with minimum constant ratio of 1.20, and second‐degree polynomial regression equations were best fitted to all the test treatment conditions. The mortality of diapausing C. partellus individuals varied between 7.0% and 37.3% under different constant and varying temperature and photoperiod regimes, which at 38°C + 14L:10D reached upto 100.0%. However, the exposure to 30°C + 12.5L:11.5D and 32°C + 13L:11D along with dry food accelerated the process of estivation, wherein the diapause larval survival was significantly higher and overall mortality of individuals due to diapause was lower suggesting these conditions appropriate for induction of estivation in C. partellus. These studies have implications for better understanding the bioecology and population regulation system under varying climatic conditions and devising novel strategies for management of C. partellus.

Diapause is an endocrine controlled arrested metabolic state to delay development or reproduction under unfavorable conditions. to gain an understanding of importance of diapause for ecological adaptation, it is important to study regulation of diapause in insects. We examined genetics of diapause in Chilo partellus by crossing the hibernating (HD), aestivating (AD), post-hibernating (pHD), post-aestivating (pAD), and nondiapause (nD) strains. Reciprocal crosses were also made to gain full understanding of diapause regulation and the maternal effects, if any. Data were recorded on fecundity, egg hatching, larval survival, diapause induction and termination, adult emergence, and morphometrics of larvae, pupae and adults in the parents (p 1 , p 2), f 1 hybrids, and the reciprocal crosses. Genetic analysis showed that AD strain is general combiner, which also improved egg hatching, larval survival, diapause termination, adult emergence and proportion of females in the progenies. incidence of diapause was highest in HD × AD, whereas termination was greatest in pHD × AD. However, nD strain and its reciprocal crosses with other strains did not exhibit any noticeable developmental response associated with diapause. Specific combining ability analysis suggested that where PHD and AD strains exist together there will be likely reduction in diapause incidence, increased survival with greater fitness and faster multiplication of their progenies resulting in outbreak of C. partellus. Degree of dominance estimates revealed that diapause, developmental and morphometric traits in C. partellus are governed by over dominance gene effects, and mainly depend on parental diapause history. Diapause is an endocrine controlled physiological state of arrested metabolic activity during a particular stage of insect development to survive under predictable adverse climatic conditions 1-4. This happens to control the physiological processes and morphological development during particular stage of life cycle. The insects undergoing diapause pass through a series of physiological events such as suppression of development and reproductive functions, arrested metabolic activity to conserve the reserves, and resumption of normal developmental process on the onset of optimum climatic conditions 3,5-7. Differences in genetic basis of various components of diapause also vary in different insect species 8. Diapause being an adaptive but genetically regulated trait provide phenotypic plasticity to insects in response to environmental conditions 6. Abiotic factors like cooling and freezing, and rates of temperature change influence developmental and physiological alterations 9-11 , which also lead to several morphological changes such as body color, length, weight and width of various hard sclerotized structures like head capsule, mandible and body appendages 12-15. Moreover, wider geographic distribution leads to behavioral and physiological differences in populations inhabiting different ecological niches 16. Existence of ecotypes in different insec...

We investigated the effects of mating among different‐aged males and females on reproductive physiology, progeny production, and longevity of Chilo partellus (Swinhoe) adults under laboratory conditions. Present studies involved virgin males (M) and females (F) of three different ages namely, on the day of emergence (1D), next day (2D), and further next day (3D), thus comprising of a total of nine mating treatments (1DM × 1DF, 1DM × 2DF, 1DM × 3DF, 2DM × 1DF, 2DM × 2DF, 2DM × 3DF, 3DM × 1DF, 3DM × 2DF, and 3DM × 3DF). The observations were recorded on fecundity, fertility, hatchability, and longevity of male and female adults. We found that mating among old aged males and females significantly reduce fecundity, fertility, and egg hatchability. Further, the fecundity, fertility, and egg hatching were significantly higher when newly emerged females mated with either of the ages of males as compared with other mating treatments. Conversely, the 3‐day‐old females, when mated with either of the ages of males, laid more numbers of unfertilized eggs, thus reduction in egg hatchability. Mating among newly emerged adults significantly reduced the longevity of male and female adults. Kaplan–Meier estimation showed that none of the adults across mating treatments survived more than 6 days. The recovery of spermatophores from the reproductive tract of females from 3DM × 1DF were significantly higher than other mating treatments. However, no association was found between spermatophore recovery and longevity of male and female adults. Findings of present studies will help to devise appropriate techniques to disrupt mating and suppress C. partellus population under field conditions.

The Chilo partellus (Crambidae: Lepidoptera) larvae undergoes both hibernation and estivation in India. Although, much has been done on reproductive physiological aspects, little is known about biochemical changes happening during hibernation and estivation in C. partellus. Thus, we mapped changes in amino acid and lipophilic profiles of C. partellus larvae while undergoing hibernation and estivation using high-performance liquid chromatography and gas chromatography mass spectroscopy. The studies revealed higher amounts of amino acids namely, serine, glycine, histidine, arginine, proline, tyrosine, and methionine in estivation, while lower in hibernation as compared with nondiapause larvae of C. partellus. Furthermore, the amounts of aspartic acid, glutamic acid, and alanine in hibernation, and threonine, valine, isoleucine, phenylalanine, and leucine in estivation were on par with nondiapause larvae. The lipophilic compounds namely, linoleic acid, stearic acid, eicosanoic acid, and n-pentadecanol were lower in hibernation than estivation and nondiapause larvae of C. partellus. Palmitoleic acid and methyl 3-methoxytetradecanoate contents were higher in hibernation than estivation and nondiapause, while myristic acid and lathosterol contents were higher in estivation than hibernation and nondiapause larvae of C. partellus. Cholesterol content was higher, while squalene and gamma-ergostenol were lower in hibernation and estivation as compared with nondiapause larvae of C. partellus. These findings suggest that certain amino acids may be constituents of heat-shock proteins and help C. partellus during estivation.However, the lipophilic compounds could be helpful in maintaining development during hibernation and estivation in C. partellus.