Differences in responses to α-pinene and ethanol, and flight periods between the bark beetle predators Thanasimus femoralis and T. formicarius (Col.: Cleridae)

Abstract

The responses of the bark beetle predators Thanasimus femoralis (Zett.) and Thanasimus formicarius (L.) (Col.: Cleridae) to a combination of α-pinene and ethanol, and Pheroprax ®, the aggregation pheromone of Ips typographus (Col.: Scolytidae), were estimated using baited and unbaited flight barrier traps in central Sweden in 1996 and 1998. In addition, the flight periods of the two Thanasimus species were analysed on the basis of trap catches. Egg development and egg loads of T. formicarius were estimated by dissecting females caught on different dates, and counting the number of medium sized and large eggs in the ovaries. T. femoralis was strongly attracted to Pheroprax ®, but almost no individuals were caught in the traps baited with α-pinene and ethanol. In contrast, T. formicarius was strongly attracted to both kinds of baits. The flight periods of the two Thanasimus species were markedly different. T. formicarius initiated flight in early spring, at about the same time as the first bark beetle species, Tomicus piniperda and Hylurgops palliatus, began to fly. The flight period of T. femoralis started later in the spring, at about the same time as that of I. typographus. Medium sized and large eggs were not present in the ovaries of T. formicarius in the beginning of the flight period. Thereafter, during the major part of the flight period, most females carried medium sized eggs while large eggs occurred mainly in the first half of the flight period.