Offspring chemical cues affect maternal food provisioning in burrower bugs, Sehirus cinctus

Abstract

Female burrower bugs (Sehirus cinctus, Hemiptera: Cydnidae) show extended care for their offspring. They guard their clutch and feed the hatched nymphs up to the third larval instar. Previous research indicated that nymphs partly regulate maternal food provisioning, but how nymphs accomplish this is unknown. We tested the hypothesis that nymphs solicit maternal provisioning by condition-dependent chemical signalling and we postulated the existence of a solicitation pheromone. Clutches of 30 nymphs were handreared in either low- or high-food conditions. After moult to second instar, cuticular compounds were extracted in hexane. An independent set of test mothers caring for offspring were subsequently exposed to extracts of nymphs from either the low- or the high-food treatment. Two control groups were also involved, one exposed to the solvent hexane and one with no treatment. As predicted for a solicitation pheromone, test mothers exposed to extracts from nymphs reared under low food provisioned more than those exposed to extracts from nymphs reared under high-food treatment. Contrary to our expectation, however, nymph extracts had an overall inhibiting effect on maternal provisioning. The effects of extract exposure on maternal provisioning were short-lasting, suggesting that the critical cues may be volatile. Our results suggest complex chemical communication in burrower bug families for the short-term regulation of maternal provisioning, potentially involving both provisioning-releasing solicitation pheromones and inhibiting chemical cues.