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Dry and Wet Season Polymorphism in the Butterflies, Melanitis Leda and Mycalesis Mineus (satyridae: Lepidoptera)

A. T. M. F. Islam
Institute of Food & Radiation Biology, Atomic Energy Research Establishment, G..P.O.Box-3787, Dhaka-1000

M. A. Razzak
Institute of Food & Radiation Biology, Atomic Energy Research Establishment, G..P.O.Box-3787, Dhaka-1000

M. H. Islam
Institute of Food & Radiation Biology, Atomic Energy Research Establishment, G..P.O.Box-3787, Dhaka-1000

A. S. M. Saifullah
Institute of Food & Radiation Biology, Atomic Energy Research Establishment, G..P.O.Box-3787, Dhaka-1000

K. Endo
Department of Physics, Biology & Informatics, Faculty of Science, Yamaguchi University, Yamaguchi 753-8512, Japan

Akira Yamanaka
Department of Physics, Biology & Informatics, Faculty of Science, Yamaguchi University, Yamaguchi 753-8512, Japan

Abstract/ Executive Summary:

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.

Keywords: Butterflies, Seasons, Polymorphism, Melanitis leda and Mycalesis mineus

Location: Kaliakyar, Gazipur,

Start Date: 01-01-2008

End Date: 31-12-2008

Program Area: Pest Management

Commodity: Insects

Objectives:

This paper addresses their seasonal changes in the wing phenotype, and fluctuation in the number (WSF and DSF) of both species. It also suggests possible factors inducing phenotypic change of DSF and WSF in M. leda and M. mineus.

Methodology:

The butterflies (Melanitis leda and Mycalesis mineus) were collected from five different areas in the deciduous forests at Kaliakyar, Gazipur. Field surveys and collections of butterflies were carried out throughout the year (January to December) in 2008. The 5 research sites were visited on sunny days of every month (2008) and butterflies were collected by using insect nets. Collected butterflies were immediately killed by pressing the thorax carefully for minimizing damages to their external organs (scales, legs and wing veins), put in triangular envelopes of papers and brought to the laboratory. Date, time and place of collection site were recorded for each specimen. Meteorological data of each collection day were recorded and summarized in Table 1. Seasonal forms identification: Species of butterflies were identified according to the Specimen Books of Butterflies (Islam et al. 2007; Pinratana, 1988). Polymorphic forms (WSF and DSF) were identified according to the characteristics of their wings, such as shapes (angular/regular) and patterns (presence or absence of eye-spots, colour and band pattern). The body portions of butterflies were represented by terms used by Islam et al. 2007. Photography: Photographs of butterflies (dorsal and ventral sides) were taken by a digital camera (Nikon, COOLPIX 5700, 5.0 mega pixels), uploaded into a personal computer and processed by using imaging software of Adobe Photoshop LE₅. Variations of the wing patterns of DSF and WSF adults of M. leda and M. mineus

Source of Information: Univ. J. Zool. Rajshahi Univ. Vol. 29, 2010 pp 33-40

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In tropical and sub-tropical areas near the equator, photoperiod, the length of which shows a little fluctuation, may not be a suitable indicator for butterflies to determine the seasonal morphs development, such as WSF and DSF. In Satyrinae, the environmental factors regulating the seasonal morph development (WSF and DSF) were not apparent yet. However, we have an interesting report that WSF adult of M. leda were developed in the wet season by subjecting larvae to a relatively low humid (60%) condition. The seasonal fluctuation in the number of M. leda and M. mineus were more or less similar in the series of above results. The turnover from DSF to WSF coincided with rising temperature when increase in humidity and food plants occur. In contrast, the turnover from WSF to DSF was found at declining temperature, resulting in low humidity and less food plant. Seasonal polymorphism is linked with seasonal changes in breeding status which in turn is associated with changes in habitat favourably. The results of our study imply that temperature, photoperiod and humidity play a crucial role in regulating seasonal morphs development in M. leda and M. mineus.

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