PARACOROTOCA AKERMANI (waRREN). 355 



smooth internal sac, and apparently this cannot be everted 

 very far out of the chitinous penis or middle lobe. 



The chitinous penis-tube is very long and can project 

 beyond the head ; doubtless copulation takes place in front 

 with the beetles facing* each other. 



(8) The brain and ventral nerve-cord are very similar in 

 Paracorotoca and Termitomimus. The cone and rhab- 

 dome cells, the optic plate and optic ganglion tend to be 

 defective in both beetles, and this condition is doubtless 

 associated with the absence of an appreciable amount of light 

 in the termite nest. 



There is a relative scarcity of cortex in the procerebral 

 lobes, and the mushroom-bodies are poorly developed. It is 

 suggested that the parasitic life has induced a low mental 

 development. 



In the full-grown larva Paracorotoca there is retained a 

 primitive embryonic condition with reference to the nervous 

 system, in that a mandibular commissure is separate from the 

 suboesophageal ganglion. 



In the imago Paracorotoca and T e r ni i t o m i m u s the 

 abdominal nerve-chain is concentrated into a single ganglionic 

 mass which is fused with the metathoracic ganglion. 



In the larva Paracorotoca there is a more primitive 

 abdominal nerve-chain with separate pairs of ganglia, but 

 they do not lie in their appropriate segments; they are 

 crowded together and are drawn towards the thorax. 



(9) Physogastrism is very marked in the imago of both 

 Paracorotoca and Termitomimus. In the larva Para- 

 corotoca it is not so conspicuous, but even here the abdo- 

 men is considerably inflated. In the larva the expansion of 

 the body is due to the great development of the fat-tissue 

 and to the large size of the niesenteron. In Termitomimus 

 imago it is due to the size of the mesenteron, the amount of 

 fat-tissue and to some extent the hypertrophy of the genital 

 organs. In Paracorotoca imago it is due mainly to the 

 hypertrophy of the mesenteron and of the genital organs. 



(10) In termitophilous insects there appears to be some 



