Vol. 104, No. 3. May & June, 1993 133 OVERWINTERING AGGREGATIONS OF FEMALE BRACHYMERIA INTERMEDIA (HYMENOPTERA: CHALCIDIDAE). 1 Paul W. Schaefer 2 ABSTRACT: Discovery of 24 overwintering female Brachymeria intermedia in a single aggregation in a window sash in an unheated building; a single female in an attic window 7.4 m above ground; a cluster under felt (tar) paper in a dog house; and in naturally occur-ring dead stumps or trees all suggest that any dry, well protected site is suitable for overwintering. The introduced polyphagous pupal parasite Brachymeria intermedia has spread throughout much of the northeastern United States and Canada in close association with its principle host, the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae). Two, possibly three, generations may occur during a season (Leonard 1 98 1 ). Adult females of both generations overwinter while males die off before winter (Dowden 1935). Dowden (1935) speculated that overwintering adults "probably hibernate under the bark of dead trees or in similar places". Only decades later are we beginning to fully understand where overwinter-ing occurs. In Japan, Gyotoku (1957) found overwintering Brachymeria lasus (Walker) (as obscurata) under the bark of a Chamaechyparis obtusa Endl. (Cupressaceae) tree with two aggregations totaling ca. 30 wasps on the lower 1.8 m of the south facing side of the trunk. In laboratory experiments, Simser and Coppel (1980) showed the presence of a chemical that led both B. lasus and B. intermedia to choose previously used or conditioned overnight resting sites versus new or unconditioned sites. They speculated that this chemically mediated aggregating behavior might extend to overwintering individuals. Pro-duced by adults of both sexes, this aggregation pheromone from B. inter-media was later identified as 3-hexanone (Mohamed and Coppel 1987). Waldvogel and Brown (1978) first reported the discovery of overwin-tering Brachymeria intermedia. Groups of 5 to 15 females where found in tunnels made by wood borers in a dead Quercus prinus L. tree in central Pennsylvania. A similar discovery was made 6 January 1983 by Robert Grebeck (USDA, BUR, Newark, DE) when ca. 1 5 females were found ca. 60 cm. off the ground in a dead Pinus rigida Mill, stump in Belleplain, Cape May Co., New Jersey (B. Grebeck, pers. comm.). 1 Received December 23, 1992. Accepted March 15, 1993. 2 USDA, ARS, Beneficial Insects Introduction Research Unit Newark, Delaware, 19713. ENT. NEWS 104(3): 133-135. May & June, 1993
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