TEMPERATURE-DEPENDENT DEVELOPMENT IN AN OREGON POPULATION OF HARMONIA-AXYRIDIS (COLEOPTERA, COCCINELLIDAE)

The multicolored Asian lady beetle, Harmonia axyridis (Pallas), an aph idophagous coccinellid, was first seen in Benton County, OR, in 1993. Coincident with the Ist occurrence of H. axyridis, we initiated a stud y on its temperature-dependent survival and development. Survival from 1st instar to adult emergence ranged from 83-90% between 18 and 30 de grees C, and at 10 and 34 degrees C was 42 and 25%, respectively. Mean time for complete development ranged from 14.8 d at 30 degrees C to 8 1.1 d at 14 degrees C. No eggs hatched at 10 degrees or 34 degrees C a nd no Ist instars transferred to 10 degrees C: survived. The mean lowe r threshold for egg-to-adult development of 11.2 degrees C is typical relative to other temperate aphidophagous Coccinellidae and was not si gnificantly different from 10.5 degrees C calculated for a French popu lation of this beetle. Conversely, the mean number of degree-daps (DD) required for complete development was higher in the Oregon population (267.3 DD) than the French population (231.3 DD), although this may h ave been due in part to a different diet. Times for preimaginal develo pment and values for thermal requirements suggest that the species is a thermal generalist in western Oregon.