The initially phytophagous caterpillars of Maculinea alcon and M. rebeli complete their development in Myrmica ant colonies as social parasites. Recent genetic studies show no differences at the species level among various populations of each butterfly taxa. Usually M. alcon and M. rebeli are identified by habitat and larval food plants (Gentianaceae) and host ant specificity is also considered to be an important feature. However most of the ecological characteristics overlap at least in some parts of their distributions. The developmental and survival characteristics of caterpillars reared by different Myrmica species were compared in laboratory experiments and in the field. Morphologically indistinguishable M. alcon and M. rebeli, which originated from Polish populations, are very similar in terms of host specificity i.e. larvae survived both with M. scabrinodis and M. sabuleti. However they showed different growth characteristics. The earlier flight period of M. rebeli, which is synchronized with the phenology of Gentiana cruciata, resulted from the quick growth of caterpillars in Myrmica nests in the pre-winter phase, when they gained about half of their final body biomass. After the end of winter they recommenced growth almost immediately. M. alcon larvae entered diapause shortly after adoption by ants and began to increase in weight significantly just one month after the onset of spring, which synchronized their development with that of their larval food plant, G. pneumonanthe. Therefore neither population group is transferable between habitats and should still be regarded, at least, as distinct conservational units.
Facultative diapause in the wax moth, Galleria mellonella, occurs in the final larval instar. Application of juvenile hormone analogs (JHAs) to the larvae of this species has similar effects to diapause, in terms of prolonged development of the larval stages and the arrest in the metamorphosis of internal organs. Here, we focus on testes development and spermatogenesis at the end of larval development in G. mellonella, how they are affected by diapause induced by an environmental decrease in temperature to 18°C and the application of a JHA (fenoxycarb) to larvae. Because neither testis development nor spermatogenesis are described in detail for this species, we examined them in individuals not in diapause during the period from the last larval instar to the newly emerged adult and present a timetable of changes that occur in the development of testes in this species. These observations have increased the very limited data on the course of spermatogenesis in pyralid insects. We then used these data for comparative analysis of testes in larvae from two experimental groups: individuals in diapause and those treated with fenoxycarb. The results on the general morphology testes revealed obvious degenerative changes caused by fenoxycarb (but not by diapause), including testicular wall hypertrophy and disarrangement of testicular follicles. Moreover, treatment with fenoxycarb finally resulted in the disintegration of nearly all testicular cyst-containing germ cells at different stages of spermatogenesis, a situation never previously described in the literature. In contrast, the main effect of diapause on testes was merely the degeneration of spermatocytes in the proximal regions of the testicular follicles. Finally, the TUNEL analyses, revealed that the degenerative changes in germ cells were apoptotic in character in the testes of both individuals in diapause and fenoxycarb-treated males., Piotr Bebas, Bronislaw Cymborowski, Michalina Kazek, Marta Anna Polanska., and Obsahuje bibliografii
Nuptial flights of Crematogaster teranishii Santschi occur in autumn. Queens and possibly larvae pass the first winter without workers in Okayama, Japan. This study examines and tests the hypothesis that C. teranishii queens regulate not only their own diapause, but also that of their larvae. Some queens collected immediately after their nuptial flight in early October were exposed to a low temperature of 10°C for 3 months before transfer to 25°C; these queens started oviposition approximately 8 days after the transfer. Larvae reared by these previously chilled queens pupated synchronously until day 50. Other field-collected queens reared at 25°C without prior chilling reproduced soon after collection. They started oviposition, but the development of their larvae was arrested and pupation occurred late or not at all within the120 day experimental period. The delay in pupation in colonies in which the queens were not previously exposed to low temperature strongly indicates that many larvae are in diapause. Because eggs and larvae were not exposed to low temperatures, they were unable to determine the developmental pathway providing the best response to environmental factors. Results indicate that queens regulate whether their larvae undergo diapause.
In the field, the blister beetle Mylabris phalerata Pallas (Coleoptera: Meloidae) undergoes larval diapause in the ground, which lasts for nearly six months. The effect of the soil environment on this diapause was examined. Final instar larvae kept at temperatures of >= 26°C do not enter diapause and continued to develop regardless of the soil water content and photoperiod. Below 25°C the final instar larvae entered diapause regardless of soil water content and photoperiod. The early stages, particularly L2, appeared to be more important for diapause induction than the later stages. However, the other instars were also sensitive. Temperature, rather then photoperiod was the main factor influencing pupal duration.