Oothecal Deposition and Concealment

The majority of oviparous type A cockroaches select and prepare a site for egg case deposition with some care (Chapter 9; Roth and Willis, 1960; Roth, 1991a), and the stereotyped behavioral sequences involved have been used as taxonomic characters (McKittrick, 1964). Therea petiveriana simply deposits oothecae randomly in dry leaves (Ananthasubramanian and Ananthakrishnan, 1959). Other species attach them to the substrate (with saliva or genital secretions), and many find or construct a crevice,

Fig. 7.2 The diurnal Australian cockroach Polyzosteria mitch-elli digging a hole for hiding her ootheca. It is a beautiful species, with a bronze dorsal surface spotted and barred with orange or yellow, a pale yellow ventral surface, and sky-blue tibiae. The lively colors fade after death. Photo by E. Nielsen, courtesy of David Rentz.

Fig. 7.2 The diurnal Australian cockroach Polyzosteria mitch-elli digging a hole for hiding her ootheca. It is a beautiful species, with a bronze dorsal surface spotted and barred with orange or yellow, a pale yellow ventral surface, and sky-blue tibiae. The lively colors fade after death. Photo by E. Nielsen, courtesy of David Rentz.

glue the ootheca in a precise position inside it, then conceal it with bits of debris, pieces of the substrate, or excrement (Fig. 7.2). Ootheca concealment is known in blattids (e.g., Blatta orientalis, Eurycotis floridana, Methana marginalis, Pelmatosilpha purpurascens, Peri-planeta americana, P. australasiae, P. brunnea, P. fuliginosa), blattellids (Ectobius sylvestris, Parcoblatta pennsyl-vanica, Supella longipalpa, Loboptera decipiens, Ellipsidion affine, Ell. australe), and cryptocercids (Cryptocercus punctulatus). In the latter, wood and saliva are used to pack oothecae into slits carved in the ceilings of their wood galleries; the keels of the oothecae are left uncovered (Nalepa, 1988a). Concealment behavior may vary among closely related cockroach species. Female Ectobius pallidus, for example, carefully bury their oothecae after deposition; E. lapponicus and E. panzeri seldom do (Brown, 1973a). Intraspecific variation in this behavior may depend to some extent on the substrate on which the insects are found or maintained. Nyctibora noctivagasim-ply drops its ootheca in the laboratory, but in Panama, oothecae were found glued to leaves and in crevices of the piles supporting a house (McKittrick, 1964). Although females whose eggs absorb water from the substrate have to be exceptionally discriminating in where they place oothecae, they do not always make wise choices. In five species of Parcoblatta, it is common to find shrunken oothecae, as well as oothecae that have burst and extruded material from the keel (Cochran, 1986a). A great many unhatched and shriveled oothecae of Parc. pennsyl-vanica were found under the bark of pine logs in an early stage successional forest by Strohecker (1937); mortality was attributed to the high temperature of logs exposed to direct sunlight. In species that leave oothecae exposed, the egg case may be cryptically colored. Shelford (1912b) described the ootheca of an unknown species from Ceylon (now Sri Lanka) that was attached to the upper surface of a leaf. It was white, mottled with brown, and looked "singularly like a drop of bird's excrement."

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