Squelette et musculature des regions genitales et postgenitales de la femelle de Thermobia domestica (packard). Comparaison avec la region genitale de Nicoletia sp. (Insecta: Apterygota: Lepismatida)

Abstract

The lepismatids show clearly the modifications brought about by the presence of the female genitalia upon the arrangement of the segmental constitutents. These modifications follow an antero-posterior and a ventro-posterior gradient. The influence begins in the seventh segment and still exists in the tenth segment. The maximum is seen in the ninth segment where the tergite is also modified. The gonocoxites VIII of Thermobia domestica are comparable to the coxites VII of Nicoletia sp. The valves VIII go forward as far as the sternal areas (reduced but still recognizable). This penetration is less pronounced in Nicoletia. The valves IX are more forward relative to the position of the gonocoxites IX and the sternal areas are no longer recognizable as sclerites. The gonocoxites IX are much modified : the antero-dorsal angle separates itself from the primitive coxite and forms an individualized sclerite (gonangulum) which is articulated with the tergite ; also, in the Lepismatids, this sclerite has the characteristics of the second valvifer of the Pterygota. The rest of the coxite extends and partially surrounds the valve ; this modification may lead to the dorsal valve of the orthopteroid type. Nicoletia shows more primitive characters than Thermobia concerning the ventral pregenital areas and reminds those of the machilids ; we have shown that the “languette” which covers the base of the genital valves must be interpreted, not as a sternite VIII, but as the result of the development of a presternal area ; this “languette” appears to be the precursor of the subgenital plate of the Pterygota. The primitive structure of the eleventh segment in Thermobia with cerci and the coxosternal areas is interesting.