Preferred host stages, clutch size, and sex allocation by Cirrospilus coachellae (Hymenoptera: Eulophidae), a parasitoid of the citrus peelminer Marmara gulosa (Lepidoptera: Gracillariidae) with a view to its rearing and release as a biological control agent

Abstract

Abstract Cirrospilus coachellae Gates (Hymenoptera: Eulophidae) is the principal parasitoid of larvae of the citrus peelminer, Marmara gulosa Guillen and Davis (Lepidoptera: Gracillariidae), in the desert grapefruit region of southern California and Arizona. M. gulosa or possibly a congener has recently been introduced into the San Joaquin Valley of central California, but without the parasitoid. Efforts have been underway to rear and release C. coachellae from southern California, so far without any success, and now Mexico. It is a synovigenic, facultatively gregarious, ectoparasitic idiobiont, whose clutch size depends on the size of its host. C. coachellae prefers the larger, sapfeeding instars (⩾0.35 mm) to which it allocates one to ten offspring per host larva (x = 2.5/host) infesting grapefruit both in the laboratory and the field. The sex ratio of C. coachellae offspring allocated to a M. gulosa larva is female biased both in the laboratory and the field and consisted mostly of a single male offspring coupled with a clutch of several female offspring or, less frequently, two male offspring associated with clutches of several female offspring. However, the pattern of sex allocation was more female biased for parasitoid clutches allocated to hosts parasitized in the laboratory than in the field and similarly sized clutches were more likely to be all female and they were allocated to larger hosts in the laboratory rearings than in the field parasitized hosts.