INFECTION OF COCKROACHES WITH HERPOMYCES (LABOULBENIALES). I. LIFE HISTORY STUDIES

¹ Department of Entomology and Economic Zoology, University of Minnesota, St. Paul 1, Minnesota

1. Herpomyces stylopygae Speg. is shown to be distinct fromH. periplanetae Th. by host specificity tests.

2. Spores of H. stylopygae are found all over the surface of oriental cockroaches but mature plants are mostly found on the antennae, seldom on palpi and only rarely elsewhere. They grow on setae or on hard or soft cuticle but only on a living cockroach. Infections are heavier on males and on adults and experiments show the infection is disseminated by contact.

3. The ascus contains 8 spores which it liberates within the perithecium through a terminal perforation, leaving the ascus as a fluid-filled ghost.

4. Spores are ejected from the perithecia in various numbers, not just in pairs (Table I). Mostly the groups protruding from the subterminal apertures of the perithecia (Fig. 2) consist of 1-4 spores but groups as large as 12 spores were found. The presence of single, paired and multiple spore groups protruding from perithecia and found on the surface of hosts is correlated with the presence of single, paired and multiple plants on infected cockroaches.

5. Antennae of infected cockroaches serve as efficient spore brushes and dusters.

6. Spores become firmly attached to the cockroach's cuticle by holdfasts developed at both ends.

7. Development from spore to mature perithecia takes nearly two weeks.

8. The volume of a female plant is 3500-20,000 times that of a spore. So much material cannot be obtained from a minute volume of cuticle. A tubular haustorium through the cockroach's cuticle was found to expand into a large bulb in the epidermal cell layer.

9. Infections on adults persist but infections on nymphs were found to be completely lost when the nymph molts. The fungus plants are found intact on the shed skin.

10. There appears to be no development of resistance since individuals freed of infection by molting can be readily reinfected.

11. Some notes are given on spore structure, and on differences shown by H. ectobiae.