SEROSA ONTOGENY IN 2 EMBRYONIC MORPHS OF COPIDOSOMA-FLORIDANUM - THE INFLUENCE OF HOST HORMONES

The embryos of 2 larval morphs of the insect parasitoid Copidosoma floridanum (Ashmead) (Hymenoptera: Encyrtidae) were readily distinguished on the basis of temporal and morphological characters. Although larvae of the 2 morphs differed in morphology and timing of hatch, both morphs derived a serosal membrane just prior to embryonic morphogenesis. Nuclei of the serosa increased in diameter and ploidy during development. Serosa polyploidy was similar in both morphs at identical stages of morphogenesis. Host endocrine perturbations that blocked C. floridanum morphogenesis also affected serosa development. Serosa ontogeny was blocked when the host was ligated at 7 h of the 4th stadium. Daily application of the juvenile hormone analogue methoprene starting at 20 h of the host's 3rd stadium resulted in serosal nuclei with greater diameters and ploidy values than those of untreated embryos. Treatment of the host with methoprene beginning at 20 h of the 3rd stadium followed by ligation at 7 h of the 4th stadium arrested serosa ontogeny and embryonic growth of the parasitoid. These data indicate that embryos of both morphs of C. floridanum formed a serosa just prior to morphogenesis and that serosa ontogeny required host head factors. Furthermore, host juvenile hormone did not influence serosa ontogeny but stimulated polyploidy of membrane nuclei.