The Ecology of the Bat Ectoparasite Eoctenes spasmae (Hemiptera: Polyctenidae) in Malaysia

Abstract

The Polyctenidae are a small family (5 genera, 32 species) cf wingless, viviparous bugs which live exclusively and permanently as blood-sucking ectoparasites upon certain microchiropteran bats. Knowledge of the taxonomy, morphology and anatomy, and biology of the family is reviewed. Eoctenes spasmae is typical of the family in being host-specific to a single species of bat. On its host, Megaderma spasma, E. spasmae occurs on all parts of the body but particularly in the hollow formed by the head and shoulder blades where it is well protected from host grooming. It never leaves the body, and transference to another host can only occur through body contact. Feeding is frequent, and if starved nymphs die within six hours and adults within 30 hours. For 27 bats captured for the first time the incidence of infestation was 85 percent with 13.7 bugs per bat, the two sexes being equally infested. Of the 370 bugs removed from these bats 25 percent were males, 38 percent females, and 37 percent nymphs. Assuming the sexes are produced in equal numbers, the significant predominance of females over males indicates that males are shorter lived, perhaps because they are more active and thus more liable to host predation, the major cause of mortality. There was no indication of seasonal variation in the biology of E. spasmae in the humid equatorial climate of Malaysia. THE POLYCTENIDAE (Hemiptera: Heteroptera: Cimicoidea) are a small family of blood-sucking bugs which live exclusively and permanently upon certain microchiropteran bats. They are adapted in a variety of ways for their ectoparasitic life in the fur of nocturnally flying mammals, the body being dorsoventrally flattened and covered with many backward-pointing setae and combs (ctenidia); they lack eyes and wings but have well-developed legs and bear their young alive (fig. 1). Since the description of the first species in 1864 and the erection of the family 10 years later, their taxonomy has become fairly well known (Ferris and Usinger 1939, 1945; Usinger 1946; Maa 1964; Ueshima 1972). Indeed no valid new genus has been described since 1922 although the number of known species has tripled since then: there are now five genera and 32 species (Jordan 1922a, b; Marshall 1981b; Ryckman and Casdin 1977). Their external morphology has been described by Jordan (1912a) and Ferris and Usinger (1939), but few details of their internal anatomy or their biology are known; indeed there are no recorded observations upon living insects. Their viviparity was first described by Jordan (1911, 1912b), and their embryogenesis by Hagan (1931, 1951). Maa (1959) was the first to recognize that they possessed three nymphal instars. Ferris and Usinger (1939) and Maa (1964) provided a complete bibliography to the family to date. The region surrounding the Indian Ocean is probably the original home of both bats and polyctenids. In Malaya (West Malaysia) 86 species of bats occur (Medway 1978), but only t-wo-three species are parasitized by polyctenids: Taphozous melanopogoz Temminck (Emballo,nuridae) are parasitized by Eoctenes interrnedius (Speiser), Megac'ermna spasma (L.) (Megadermatidae) by Eoctezes spasniae (Waterhouse), and possibly Megadermia lyra Geoffroy by Polyctenes molossus Giglioli. While in West Malaysia, I rook the opportunity of making observations upon the ecology of one member of this family, E. spasinae.