A Sixteen-Year Study on the Bivoltinism of Anomala flavipennis (Coleoptera: Scarabaeidae) in Mexico

Abstract

Seasonality and abundance of the scarab beetle Anomala flavipennis Burmeister were studied using a black light trap in Rio Bravo, in northern Tamaulipas, Mexico, from 1979 to 1994. A bivoltine life cycle in A. flavipennis was evident throughout the period of study as shown by 2 distinctive flight periods: one from mid-April to mid-May (spring or overwintering generation) and the other from late August to late September (fall generation). Bivoltinism of A. flavipennis in northeastern Mexico, as compared with univoltinism of this species in the United States (e.g., Georgia, Kansas, Nebraska), is attributed to the warmer, subtropical climate of the former, where annual heat units nearly double those accumulated in northern parts of the range of this beetle. An average of 1,174 and 3,509 accumulated heat units (>10°C) starting 1 January was required for 50% adult emergence in the spring and fall generations, respectively. However, heat units resulted in a more variable parameter than did Julian dates for predicting emergence of A. flavipennis . Although rainfall appeared to trigger A. flavipennis adult emergence during the fall, the influence of rainfall was not as clear during the spring, probably because of the irrigation practices in this region during the spring growing season. Captures were generally greater during the fall than the spling, with a maximum of 21,444 adults having been captured on 7 September 1994. Abundance (total captures during spring or fall) of A. flavipennis was not associated with temperature and precipitation. Abundance of A. flavipennis during the spring season depended on the adults captured during the previous fall. However, fall generation did not depend on abundance of adults emerging during the previous spring.