ADAPTIVENESS OF PARENTAL CARE IN PARCTSTRACHIA-JAPONENSIS (HEMIPTERA,CYDNIDAE)

To understand the adaptiveness of the advanced parental care seen in P arastrachia japonensis Scott, some characters of egg guarding and prog ressive provisioning were examined through field experiments and obser vations of natural nests. A carabid beetle is the first known predator of this species. Females of P. japonensis could not distinguish their own eggs from those of other females and guarding of eggs against the predator was strictly defensive; they primarily used their bodies as shields or escaped with the egg mass. The sole food resource, drupes o f the deciduous tree Schoepfia jasminodora (Sieb. et Zucc.), is scarce and ephemeral, and, because conditions around the host tree are gener ally unsuitable for nesting, most nests are located well out of range of the fallen drupes. Females repeatedly left the nests on foraging tr ips and provisioned nests with drupes. Survival rate of nymphs with a female and drupes paralleled that of nymphs with only drupes when the danger from predation was eliminated. The number of drupes provisioned was positively correlated with the duration of the nymphal nesting pe riod. Further, nymphs in nests with drupes remained aggregated longer than those in nests without drupes. Because aggregations are apparentl y essential for successful feeding in the early stages and a prolonged nesting period probably affords protection against predation and desi ccation, progressive provisioning may have evolved in response to thes e environmental pressures as well as in response to the resource const raints.