70 



THE COCKROACH I 



are reduced in size. The sternum is often altogether wanting, 

 while the tergum may unite with the metathorax. 



The externally visible appendages of the abdomen are the 

 cerci and the st}des of the male Cockroach. The cerci are found 

 in both sexes ; they are composed of sixteen rings each, and 

 project beneath the edge of the tenth tergum. They are 

 capable of erection by special muscles, and are supplied by large 

 nerves.* The sub-anal styles are peculiar in their insertion, 

 being carried upon the sternum of their segment (the ninth). 



9 



Fig. 33. Profile of Male and Female Cockroach. X 4. 



The abdominal segments are never furnished with functional 

 legs in adult Insects, but representatives of the lost appendages 

 are often met with in larvae. According to Butschli,f all the 

 abdominal segments are provided with appendages in the 

 embryo of the Bee, though they disappear completely before 

 hatching. Some Hymenopterous larvae have as many as eight 

 pairs of abdominal appendages, Lepidopterous larvae at most 

 five (3-6; 10)4 



* Jointed cerci are commonly found in Orthoptera (including Pseudo-Neuroptera) ; 

 in the Earwig they become modified and form the forceps. The "caudal filaments" 

 of Apus are curiously like cerci. 



The cerci are concealed in the American Cryptocercus, Scudd. (Fam. Panesthidce). 



t Entw. der Biene. Zeits. f . wiss. Zool. l>d. XX. Or, see Balfour's Embryology, 

 Vol. L, p. 338. 



% From more recent observations it is probable that abdominal appendages are 

 usually present in the embryos of Orthoptera, Coleoptera, Lepidoptera, and possibly 

 Hymenoptera. The subject is rapidly advancing, and more will be known very 

 shortly. 



