Risk-sensitive decisions during nesting may increase maternal provisioning capacity in the subsocial shield bug Parastrachia japonensis

Abstract 1. Females of the monophagous shield bug Parastrachia japonensis Scott provision their nymph-containing nests with high-quality drupes of the single host tree, Schoepfia jasminodora , a resource that is poor and unstable, under an array of variable environmental constraints.
2. Although the number of drupes provisioned is correlated positively with enhanced nymphal development and survival, there is great variability in the number of drupes that females provide.
3. The ability to adjust behaviour and/or physiology, i.e. make risk-sensitive decisions, should be adaptive for organisms such as P. japonensis that are confronted with extreme variability in food availability and in the conditions under which they must forage. To assess whether females of this species use risk-sensitivity to improve their provisioning success, data on the parameters of provisioning activity obtained during a long-term field study were analysed. The relationships between variation in three female-controlled factors during nesting (nest site, active stage during the provisioning season, duration of provisioning activity) and the conditions of three environmental factors (drupe availability, intraspecific competition, weather) were examined. The relationships between all of these factors and provisioning capacity of females were investigated.
5. Nest site, intraspecific competition, and timing of provisioning activity only affected provisioning capacity when drupe availability was extremely good or bad or weather was particularly bad.
6. The findings suggest that females use risk-sensitive decisions to increase provisioning capacity under extreme conditions of low and high drupe availability and inclement weather.