Experimental host.—Blatta orientalis, U.S.A. (Haber, 1920).
Relatively little detailed information was known about this wasp (fig. 5), one of the earliest parasites of cockroach eggs to be discovered, until Cameron (1957) studied its biology. Arnold (Kirby and Spence, 1826) discovered that the genus Evania parasitized Blatta, but did not know whether the wasp developed on the cockroach eggs or in the nymphs. MacLeay (Westwood, 1843) determined that Evania developed within the oöthecae of cockroaches. Westwood (1854a) found the larvae, pupae, and adults of E. appendigaster in egg cases of an unidentified species of cockroach found on orchids received from Calcutta.
Adult behavior.—Adult wasps visited flowers of parsley, Petroselium crispum, and fennel, Foeniculum vulgare (Margretti in Schletterer, 1886; Crosskey, 1951). In Hawaii the adult wasps have been seen resting on leaves coated with honey dew (Williams et al., 1931); Evania sp. were attracted to the honey dew secreted by a diaspine scale insect (Williams, 1931). Adults lived two to three weeks in captivity with ample food and water (Cameron, 1957).
Oviposition.—Shelford (1912, 1916) erroneously supposed that Evania, by means of her cleaverlike abdomen, opened the oötheca at the crista and then deposited her egg or eggs on the eggs of the cockroach. Haber (1920) observed and described oviposition. The female wasp crawled over the surface of the oötheca, actively vibrating her antennae, and settled with the axis of her body parallel to the axis of the egg case as it lay upon its right side. Lying on her right side, the wasp extended her ovipositor and punctured the oötheca in the fifth cell on the left side; she remained in this position for about 15 minutes. Cameron (1957) described similar oviposition behavior that lasted about half an hour. Kieffer (1912) and Crosskey (1951) stated that the female deposits her eggs before the walls of the oötheca harden.
Fig. 5.—Evania appendigaster. Left, dorsal view, X 8. Right, side view, X 5. (Reproduced with permission. British Museum [Natural History], 1951, figs. 1A and 1B).
Development.—Kieffer (1912) stated that the larvae in this family eat the cockroach eggs and pupate in the oötheca without forming a cocoon. Smith (1945) stated that the larva feeds on one cockroach egg after another until all are destroyed; by that time it is full grown and it pupates within the oötheca. Cameron (1957) found that there are five larval instars and that in material from Saudi Arabia there are three or possibly four generations a year.