Photoperiod and reproductive diapause in the predatory bugs Anthocoris tomentosus, A-antevolens, and Deraeocoris brevis (Heteroptera: Anthocoridae, Miridae) with information on overwintering sex ratios

The effect of photoperiod on induction of reproductive diapause was determined for 3 species of predatory bugs inhabiting the pear and apple growing regions of the Pacific Northwest. Females of Anthocoris tomentosus Pericart, A. antevolens White (Anthocoridae), and Deraeocoris brevis (Uhler) (Miridae) were more likely to enter reproductive diapause (characterized by undeveloped ovaries and well-developed fat body) under short-day conditions than under long-day conditions. Critical photoperiods were between 16:8 and 15:9 (L:D) h in D. brevis, and between 15:9 and 14:10 [L:D] h in A. tomentosus. Results for A. antevolens were less clear because females in this species often failed to reproduce even under long-day conditions (18:6 and 16:8 (L:D) h). A small number of A. tomentosus and A. antevolens that failed to mature ovaries also failed to accumulate large fat reserves. Duration of the preoviposition period in nondiapausing insects was shortest in A. tomentosus (9 d), of intermediate duration in D, brevis (10-11 d), and longest in A. antevolens (12-13 d). Overwintering sex ratios were highly biased in the 2 anthocorids (79-95% female), and were moderately biased in D. brevis (60% female). Overwintering samples of 2 other anthocorid species. Grins tristicolor (White) and A. whitei Reuter, also were female-biased (100% female for both species). Dissections of females indicated that insects having undeveloped ovaries and well-developed fat body could be collected from the field most of the summer. Numbers of teneral adults in the dissections showed peaks in late July (A. tomentosus and A. antevolens) and in early August (D. brevis).