Ecology, Environment and Conservation Paper

COCOON TRAITS AND GRAINAGE BEHAVIOUR OF MODAL ECORACE OF TASAR SILKWORM IN THREE DIFFERENT LOCATIONS OF SIMILIPAL

Aratibala Sahu, Prasanta Kumar Kar and Priya Ranjan Debata

Abstract

The wild ecorace of Antheraea mylitta “Modal” is bestowed with superior cocoon traits, but it is difficult to rear. The best option is to conserve the ecorace in its natural habitat. To save the population and for its sustainable utilization, conservation works are undertaken every year where wild cocoons are collected, eggs are produced and subsequently released on Sal trees in forest for natural proliferation. There are eight such camps in the peripheral zones of Similipal with varied geographical conditions. To understand the grainage behaviour of Modal silk moths, a study was undertaken in three different locations. The wild Modal cocoons were collected in August and around 20000 cocoons were kept in the pagoda at locations viz. Sarat, Kendujuani and Astabeda of Mayurbhanj district, Odisha. Wide ranges of variation were recorded for cocoon traits with respect to places for almost all traits except shell ratio of male (P < 0.01 to 0.001). In case of males, cocoon volume showed significant difference for places. The pupal weight was highest at Kendujuani than Sarat and Astabeda. The cocoon weight and filament length were lowest at Astabeda, whereas at par for Kendujuani and Sarat. But peduncle length was low at Kendujuani where as at par for Sarat and Astabeda. In case of females, cocoon weight and pupal weight values were significantly high at Kendujuani followed by Sarat and low at Astabeda. Shell weight and cocoon volume were significantly high for Kendujuani whereas Sarat and Astabeda were at par. But cocoon breadth and penduncle length were lowest at Astabeda where as Kendujuani and Sarat were at par. The grainage parameters were recorded from 15th August to 25th October. In Kendujuani, Sarat and Astabeda total of 7707,7206 and 7442 female moths were emerged during the entire span respectively. Since, these moths do not mate with the males of the same camp, they are taken to the forest during night for mating with external males. The total number of couplings in these three places were 4385 (56.9%), 3928 (54.5%) and 3219 (43.2%) respectively. From this it is evident that at Astabeda area of Similipal, availability of wild males in the forest is significantly less in comparison to other two areas. The pattern of emergence at one week interval also varied, early mass emergence followed by one more peak in October was recorded in Astabeda. But in other two places, almost uniform emergence with one peak in October was recorded. Thus, more attention is warranted for the proliferation of Modal populations in the Eastern part of Similipal.