Search

To establish the indices evaluating the ecological conditions of forests in Bangladesh, total number of butterflies counted in 5 observation sites reached 27,805 (76 species, 10 families). Number of butterflies (IND) and species showed bimodal pattern of seasonal fluctuations peaked in April and November-to- December. The values of I(R5) also showed bimodal seasonal fluctuations peaked in January-to-February and July-to-September. The ratios of IND/I(R5) formed a large peak in November. Results indicate that species diversities of butterflies high in March-to-July decreased thereafter, the numbers of butterflies increased toward November in the study area. Key words: Butterfly, seasonal fluctuation, population indices, ecological states  doi:10.3329/ujzru.v27i0.1958 Univ. j. zool. Rajshahi Univ. Vol. 27, 2008 pp. 67-71

In Polygonia c-aureum, there are two seasonal forms, viz., the summer form and the autumn form. Previous experiments (Endo, 1970) showed that the corpora allata of the summer form accelerate the maturation of ovarian follicles soon after imaginal ecdysis. On the other hand, the corpora allata of the autumn form do not stimulate ovarian maturation during a period of 2 to 3 weeks after the emergence. In the summer form (S) as well as in the autumn form (A), the corpora allata remained in an inactive state for about 15 days after emergence when they had been isolated microsurgically from the brain and the corpora cardiaca during the larval period. Further, when separation of the brain into the right and left hemispheres or ablation of the medial neurosecretory group cells of the pars intercerebralis had been carried out on S-pupae of 28 hr after pupation or of earlier ages, they developed into autumn form in respect to wing pattern and their corpora allata did not stimulate ovarian maturation until 2 to 3 weeks after emergence. On the other hand, when the above operations had been performed 34 hr after the pupation or of later ages, they developed into summer form in respect to wing pattern and ovarian maturation was evident soon after the emergence. In these cases, stimulation of the corpora allata is closely connected with the development of seasonal-forms of wing pattern. From these experiments, it is clear that the medial neurosecretory group cells of the pars intercerebralis in S-insects stimulate the corpora allata about 30 hr after pupation by way of the nervi corporis cardiaci and the activated corpora allata promote ovarian maturation throughout adult life. In A-insects, on the other hand, the medial neurosecretory group cells of the brain are inactive and fail to activate the corpora allata which in turn have no influence on ovarian maturation.

A field survey of butterflies was carried out in different areas of deciduous forests at Kaliakyar, Gazipur, during January-December, 2008. Seven species of satyrid butterflies were collected and two species, Melanitis leda and Mycalesis mineus were found to exhibit dry and wet season polymorphism. The dry season forms (DSFs) and wet season forms (WSFs) of the both species were distinguished by their upperside and underside wing patterns. The DSFs occurred only in the drier period (November to February) when day length was shorter than 12 hrs. at lower temperatures (24.1-20.6°C). Both the species of butterflies of the wetter period (March - October) were predominant of the WSF when day length was longer than 12 hrs. at higher temperatures (26.8-27.6°C). The fluctuations in the number of seasonal forms of M. leda and M. mineus were higher in DSF than those of WSF. The transition of DSF to WSF and WSF to DSF of M. leda was found to occur around the end of April and the early of September, respectively. But the turnover of DSF to WSF occurred around the early March and the turnover of WSF to DSF in October in M. mineus . Key word: Butterflies; seasons; polymorphism; Melanitis leda; Mycalesis mineus DOI: http://dx.doi.org/10.3329/ujzru.v29i1.9463 UJZRU 2010; 29(1): 33-39

In summer form adults of Polygonia c-aureum, the ovary develops soon after emergence and eggs mature a few days later. However, in autumn form adults, having been kept in laboratory conditions, only several mature eggs are found about four weeks after emergence. The allatectomy during the larval period prevents egg maturation in adults of both forms. When the corpora allata from the summer form of both sexes are transplanted into allatectomized adults of the autumn or summer form, the ovary develops as in the case of summer form adults. But the corpora allata of both sexes of the autumn form are not effective in inducing the ovarian maturation. Environmental factors, especially day-length and temperature during the larval period, may act through the neuroendocrine system to induce the activity of the corpora allata in the adult life.