EGG CHORION ARCHITECTURE IN STICK INSECTS (PHASMATODEA)

Comparative analysis of egg chorion architecture by scanning and trans mission electron microscopy is reported in about 50 species of stick i nsects (Phasmatodea). Particular attention has been paid to: (1) synth esis and structure of egg shell layers; (2) egg shape; (3) morphology of the external chorionic surface; (4) position and structure of the m icropylar plate and its cup; (5) morphology and details of the opercul um, including capitulum or pseudocapitulum; and (6) posterior pole dif ferentiation (the so-called polar mound). The taxonomic value of the v arious characters is discussed: some are clearly species-specific, whi le others (such as general egg shape and micropylar plate) appear to r eflect phylogenetic relationships of higher rank. Intraspecific featur es, such as the fine chorionic and opercular patterns of Bacillus and Clonopsis, have been recognized. In natural hybrids, egg chorion archi tectures were related to that of the parent species, resembling one of the parents in some cases and being intermediate between the 2. The s tudy of the Phasmatodea egg can provide much taxonomic information tha t is useful in the definition of natural groups.