Australian Termite, Mastolermes darwinensis. 143 



drawn beiieatli it), while the .so-called " pyjiidiuni " of a 

 cockroach or terinite is usually lornied by the tergite of 

 the tenth abdominal segment ; and in the interest of exact 

 usage, it would be preferable to distinguish between these 

 two types of " pygidia " by designating that of the beetle 

 a " hexapygidium " and that (jf the cockroach or termite 

 a " decapygidium." 



The condition occurring in the terminal abdominal 

 structures of the winged " male " of Mastolermes lends 

 additional weight to the view that the termites are rather 

 closely related to the cockroaches, since in both groups the 

 pygidium, " lOt," is a " decapygidium " {i. e. it is formed 

 by the tenth tergite), the paraprocts " pa " are usually 

 well developed in both types of insects, and in the male 

 of the primitive cockroach Cryjjtocercus, referred to above, 

 there are traces of the styli-bearing structures " sg " which 

 are only partially united with the ninth sternite " ha " 

 as in Mastotermes (fig. 4). On the other hand, the genitalia 

 of Mastotermes and other termites do not exhibit the well- 

 developed, asymmetrical penis valves characteristic of 

 most cockroaches, Mantids, and Zoraptera; and since the 

 termites belong to the superorder Panisoptera (composed 

 of the Isoptera, Zoraptera, Mantodea, Blattodea, etc.), 

 it is rather surprising that such primitive forms as Masto- 

 termes should not exhibit some indications of such a wide- 

 spread condition occuriing in the bulk of their relatives 

 in this group. It is possible, however, that since some 

 termites such as those here discussed have been found to 

 have developed a primitive type of ovipositor (a condition 

 occurring extremely rarely among Isoptera), still others 

 will be found in which traces of the penis valves are retained. 

 Indeed, in the winged males of Termojms, there are traces 

 of the penis valves, but they are so small and delicate that 

 one can scarcely see them, and they are quite unsatisfactory 

 for a comparative study of the structures in question. 



In Vol. 21, 1919, of the Proceedings of the Entomological 

 Society of Washington (pp. 129-151), in an article dealing 

 with the terminal abdominal structures of the most primitive 

 representatives of the Hymenoptera {i. e. the sawflies), 

 it w^as shown that the hypandrium, or plate below the male 

 genitaUa (" ha " of PI. IV, ligs. 2 and 4), is in most insects 

 formed by the sternite of the ninth abdominal segment, or 

 those preceding it, rather than by the tenth sternite, as 

 was formerly claimed. Furthermore, as is the case in 



