Prolonged development time of the bark beetle predator Thanasimus formicarius (Col.: Cleridae) in relation to its prey species Tomicus piniperda (L.) and Ips typographus (L.) (Col.: Scolytidae)
1 The generation time of the bark beetle predator Thanasimus formicarius (L.) (Col.: Cleridae) was found to be predominantly two years both in the field and in rearing experiments conducted with two of its main prey species, the pine shoot beetle Tomicus piniperda (L.) and the spruce bark beetle Ips typographus (L.) (Col.: Scolytidae).
2 Emergence of T. formicarius adults in the first summer was only observed in one of the two rearing experiments, and these individuals represented only 6% of that generation.
3 All individuals not emerging as adults in the first summer remained as larvae in their pupal chambers until the second summer. Pupae were found starting around mid-June, and adults (in pupal chambers) were found from late July through to the end of August.
4 Newly emerged adults had to feed in order to survive hibernation.
5 The existence of T. formicarius races, specialized on certain bark beetle species and with phenologies matching their hosts, could not be demonstrated. After hibernation there was no difference in feeding activity, timing of egg-laying or proportion of egg-laying females between the T. formicarius adults reared as larvae on T. piniperda (flight period in April) and those reared as larvae on I. typographus (main flight period generally starting in late May or early June) when exposed to a temperature and day-length typical of the early spring conditions prevailing during the flight period of T. piniperda.
6 T. formicarius was parasitized by Enclisis vindex (Tschek) (Hym.: Ichneumonidae) in the pupal chamber.
7 The importance of these findings for the population dynamics of bark beetles is discussed.
Document Type: Research Article
Affiliations: Swedish University of Agricultural Sciences, Department of Entomology, PO. Box 7044, S-750 07 Uppsala, Sweden
Publication date: May 1, 1999