Differential nymphal development of Blattella asahinai and B. germanica and their hybridization potential (Blattodea: Ectobiidae)

Abstract

The Asian cockroach, Blattella asahinai (Blattodea: Ectobiidae), is the closest relative of the German cockroach, B. germanica (L.), and has become a peridomestic nuisance pest in the southeastern United States. However, many basics aspects of the biology of B. asahinai, such as nymphal development and temperature thresholds have not yet been studied. The objectives of this project were to detail the nymphal development and developmental responses to temperature of B. asahinai as compared to B. germanica and examine the hybridization potential of these two species, as well as behavioral and morphological characteristics of the hybrids. In the following experiments, through measurements of nymphs, B. asahinai was estimated to have six or seven instars during nymphal development, and these results were subsequently confirmed through direct observation. Across six constant temperatures ranging from 10°C to 35°C, B. germanica had shorter nymphal development periods, fewer instars, and higher survivorship than B. asahinai. These developmental differences illuminated possible advantages that B. germanica and B. asahinai have in their respective environments. Both hybrid crosses were successfully performed, and the resulting hybrids appeared to have inherited intermediate wing morphology, allowing for flight in some hybrids. The results from these experiments will be useful in creating targeted management methods for B. asahinai based on unique biological traits that allow it to thrive in its outdoor habitat.