480 MEDICAL ENTOMOLOGY 



brought forward in support of this hypothesis is, however, far from 

 convincing. 



The senior author, as the result of feeding experiments, has shown that 

 the parasites of Kala Azar and Oriental Sore undergo their flagellate 

 stages in the mid-gut of the Indian bed bug, Cimex rotundatus. Owing 

 to the difficulty of obtaining a highly susceptible animal it has not yet 

 been possible to transmit these parasites by the bite of this bug. The 

 evidence that it carries these parasites in nature is, therefore, based on 

 the study of the development of the parasites in its mid-gut, and on the 

 fact that they do not develop into flagellates in any other blood-sucking 

 arthropod experimented with. 



Chagas has recently shown that a large reduviid bug, Conorhimis 

 megistus, is the invertebrate host of a human trypanosome, T. cruzi, 

 in parts of Brazil. There are several close allies of this bug in North 

 and South America, and at least one in the Oriental Region. 



EXTERNAL ANATOMY 



Before dealing with the classification of the Rhynchota and the 

 descriptions of the various important species, it will be convenient to 

 give a short general account of the external structure, such as that 

 of any common reduviid. As the species belonging to the genus Cimex 

 are somewhat aberrant the external anatomy of Cimex rotundatus will 

 be discussed separately. 



The body of a bug is distinctly divided into head, thorax and 

 abdomen. The head exhibits great variation in shape and in the 



manner in which it is attached to the thorax. In 

 The head 



many species of the Homoptera it is situated on the 



under surface and its distal edge is directed backwards. In the 

 Heteroptera the head is often small and inconspicuous as compared with 

 the rest of the body of the insect. In some pentatomids it is broadly 

 expanded and armed with lateral horns ; in many reduviids on the other 

 hand the head is narrow and elongated. The antennae as a rule consist 

 of four or five joints, which are nearly always long and slender. In 

 Belostoma the antennae are concealed in pits on the under surface of 

 the head, and have several branched processes ; in many coreids the 

 segments are broadly expanded. The eyes of bugs are usually situated 

 laterally and are generally prominent structures ; there are either two or 

 three ocelli situated behind the eyes. 



The thorax consists almost entirely of the prothorax, which forms 

 a large conspicuous plate of chitin, often with sharp lateral angles; 



