Bigeyed bugs (Geocoris spp.) attack pests in several crops, and at least one species (Geocoris punctipes) is produced commercially for pest control. Recent studies showed that hibernal diapause in G. punctipes is induced by short daylengths. The stage(s)/instar(s) sensitive to this cue, however, have not been identified for any member of the genus. We exposed G. punctipes to combinations of long (15:9 h, L:D) and short (11:13 h, L:D) day lengths during different portions of their development to determine the most sensitive life stages. We used 12 treatments, including bugs reared at long or short day length throughout nymphal development, as well as reciprocal switches (one photoperiod for part of their development and the other photoperiod for the remainder). Reciprocal switches were made at the beginning of the 2nd, 3rd, 4th, and 5th instars and at the beginning of the adult stage. Very high rates of diapause induction (>90%) occurred when bugs experienced short day length throughout nymphal development or when they were switched to short day length at the beginning of the 2nd, 3rd, or 4th instar, but only 26% entered diapause when switched at the beginning of the 5th instar. No individuals entered diapause when switched to short day length at the beginning of the adult stage. The converse switches showed that for diapause to occur, bugs must continue to experience short day lengths during the late instars and adult stage, which would happen in the field during late summer and autumn.
Species 1: Heteroptera Geocoridae Geocoris punctipes (bigeyed bug)
Keywords: diapause induction
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