Bioacoustics of Enyaliopsis iaculator

The call of E. iaculator is a continuous train of short but distinctly separate syllables, with syl- lables produced at the rate of only 2/sec (at 26°C); mean syllable duration is 0.04264 (SD=0.13340, n=790), with the frequency peak at 11.7–14.6 kHz (Figs. 49I–L); each syllable consists on average of 11 impulses (SD=2.101, n=104). The call is loud and readily audible to the human ear from several meters. Males usually start calling shortly after sunset from dense bushes, often very low to the ground (from a few centimeters to about 3 meters above the ground.) While calling, the male invariably hangs upside down on a thin branch and is relatively oblivious to disturbance. Calling males appear to be territorial and are spaced regularly by at least 10 m; the same tree or bush never has more than one calling male. The population in the northeastern part of the Cheringoma Plateau is unusual in that the males often sing throughout the day, including noontime. This population, however, shows no statistically significant differences from the populations elsewhere in the Gorongosa region in either the parameters of the call or their morphological characters.

Distribution and natural history. This new species is currently known only from the Gorongosa region albeit it is likely to occur throughout suitable lowland miombo habitats in the coastal region of central Mozambique between rivers Save and Zambezi. The record of 2 female specimens of E. nyala from Beira, listed as being in the collection of the Iziko Museum in Cape Town by Glenn (1991) (but currently missing from the museum’s holdings), is highly doubtful and likely represents the new species. E. iaculator is found primarily in the understory of Brachystegia miombo woodland, at elevations between 20 and 250 m . These katydids prefer shaded, dense bushes, where adults hide during the day by clinging to branches. In contrast, nymphs often spend the day under rocks and logs on the ground or in crevices of tree bark. They are primarily predaceous, capable of catching and devouring even relatively very fast prey, such as grasshoppers Zonocerus elegans Thunberg, 1815 . They also eat plant material, such as flowers and fruits. In addition to the defense provided by the hard and spiny pronotum these katydids respond to threats by squirting a powerful jet of hemolymph from a small opening on the dorsal surface of the connective membrane between the coxa and trochanter of the mesothoracic leg ( Fig. 17D ). The jet is powerful enough to reach the eyes of a person (and presumably other attackers) and it has a strong smell, similar to that produced by some leaf beetles ( Chrysomelidae ). The actual composition of the liquid and its chemical properties are still unknown, but it presumably contains compounds that predators find distasteful or toxic. In the experience of the authors the katydid hemolymph does not seem to have a discernible effect on the human skin albeit there are anecdotal cases of people having an allergic reaction following a contact with Enyaliopsis katydids. Strangely, despite having powerful mandibles, these katydids never attempt to bite the attacker. Both nymphs and adults occur throughout the year, including the dry season, and males call virtually every day of the year. In captivity adults lived for more than two years. Mating takes place on branches and lasts for approximately an hour, during which time the male produces a large spermatophylax, approximately the size of 1/3 of his abdomen ( Fig. 3B ); the female subsequently consumes the spermatophylax. Since the male cerci are non-functional, the male secures his position on the underside of the female by holding her with all his legs ( Fig. 3B ). The male refraction period is unknown but males mate multiple times, most likely throughout the year. Females lay eggs in the soil ( Fig. 4E ) by digging a hole with their short ovipositor and subsequently carefully cover the hole with soil. Eggs laid in captivity underwent a 2-year diapause before hatching. Nymphs of all stages resemble the adults in their general appearance and, unlike other Hetrodinae whose nymphs are often green, have brown, mottled coloration ( Fig. 5B ).