On the biology of the East Asian seed beetle Megabruchidius dorsalis (Fåhreus, 1839) (Coleoptera: Chrysomelidae: Bruchinae), an adventive species for Ukraine

Abstract

Results of studying the biology of the East Asian seed beetle Megabruchidius dorsalis (Fåhreus, 1839) (Chrysomelidae: Bruchinae) in the laboratory and field conditions of Kharkiv Region are presented. Mainly the fourth instar larvae and adult beetles hibernate in beans on the ground, in beans on trees and in shelters. Overwintered beetles appear in the first decade of May and do not need maturation feeding. The beans of honey locust (Gleditsia triacanthos L.) are an important factor in stimulating the start of oviposition. The beetles start oviposition only 8‒11 days after emergence if only the seeds are proposed as a substrate, but if the beans are present, the beetles begin to mate and lay eggs in two days. Fertility of females in the laboratory is 110±40 eggs. Egg mortality under natural conditions is 50–93%. Megabruchidius dorsalis did not colonize the seeds of chickpeas (Cicer arietinum L.) and lentils (Lens culinaris Medik.). The beetle inhabited 10–40 % of seeds of vigna (Vigna sesquipedalis Fruw) and common beans (Phaseolus vulgaris L.), but the 1^st instar larvae died. Most of the growing season the beetles use the seeds of Gleditsia of previous years as a fodder substrate both in the native range and in the Kharkiv Region. Only in the second half of August they inhabit the seeds of the current year's crop. In the Kharkiv Region, M. dorsalis has three generations per year like in its native range in Sagamihara (Japan). The development duration of one generation in the laboratory is 37 days at 27 ºC and 41 days at 25 ºC.