EXOTIC BIRCH-LEAFMINING SAWFLIES (HYMENOPTERA, TENTHREDINIDAE) IN ALBERTA - DISTRIBUTIONS, SEASONAL ACTIVITIES, AND THE POTENTIAL FOR COMPETITION

The exotic birch-leafmining sawflies Fenusa pusilla (Lepeletier), Prof enusa thomsoni (Konow), and Heterarthrus nemoratus (Fallen) occurred i n Alberta during 1992-1995, but only the first two were abundant. Birc h-leafmining sawflies occurred at all sites surveyed in central and so uthern Alberta, and appeared to be expanding their ranges northward. A dult F. pusilla began emerging in mid-May (approximately 220 DD05), an d there were one to three generations per year, depending on location and year. Female F. pusilla were relatively less abundant on young tha n on mature trees. Profenusa thomsoni began attacking trees in June (b etween 400 and 550 DD05), and was invariably univoltine. Both species were more abundant and were active earlier on urban trees than al a ne arby rural location. The highest catches and most complete representat ions of seasonal activity were obtained using yellow sticky traps. Lar val F. pusilla and P. thomsoni are unlikely to compete directly for le af resources because their leafmining activities are separated spatial ly and temporally, but they probably compete intraspecifically.