UNUSUAL SEX ALLOCATION IN A SOLITARY PARASITOID WASP, SPHAEROPTHALMA-PENSYLVANICA (HYMENOPTERA, MUTILLIDAE)

Sphaeropthalma pensylvanica reared from cocoons of the organ pipe mud dauber, Trypoxylon politum from Georgia over several years yielded onl y adult males. Possible explanations for this sex-biased emergence fro m this host are (1) obligatory heteronomous heterotrophy, in which the two sexes develop on entirely different hosts; (2) differential morta lity in the immature stage, with female larvae dying during developmen t; and (3) facultative size-dependent sex allocation, with female eggs laid only on hosts smaller than T. politum.