Recent range expansions of Peristenus digoneutis (Hymenoptera : Braconidae), a parasite of the tarnished plant bug (Hemiptera : Miridae), and high temperatures limiting its geographic distribution in North America

Peristenus digoneutis war; discovered in one new state (Maine) and in 15 ne w counties in Maine. New Hampshire, New York, Pennsylvania. and Vermont dur ing 1997-1999. These new records increased the number of counties where thi s parasite has been found by 42%, to a total of 51 counties in eight states . No permanent establishments of P. digoneutis have been found south of New York City, which suggests that high summer temperatures are limiting its s pread southward. A good agreement was found between the parasite's southern most establishment locations and a maximum summer temperature/duration of 3 0 degreesC (86 degreesF) for 14 to 30 days. This temperature limit suggests that P. digoneutis can disperse westward both north and south of Lake Erie , across southern Ontario and northern Ohio, to Michigan and Wisconsin. Est ablishment south of New York City (latitude 40.5 degreesN) is unlikely, exc ept possibly along the higher/cooler elevations of the Appalachian Mountain s.