HOST RELATIONS 



349 



to form the hindmost region of the intestine (Grandori, 1911 ).i 

 The greater part of the cavity of the vesicle is occupied by the 

 much enlarged terminal chamber of the heart, which suggests that 

 the organ mainly functions as a specialised type of blood gill. 

 According to Grandori, the character of its lining epithelium 

 indicates that it also plays some part in excretion (Figs. 85 and 87). 



Fig. 86. Fifth instar larva of Encyrtus infelix dissected from its 

 host while still enclosed in its sheath, s, together with the 

 longitudinal tracheal trunks, t, of the host attached, sa, anterior 

 spiracle ; sp, posterior spiracle ; t', longitudinal trachea of a 

 parasite ; ta, tracheal attachment. (From Thorpe.) 



In all endoparasitic Hymenopterous larvge there is no through 

 passage between the mid-intestine and the exterior, an arrangement 

 which ensures against the contamination of the host by faecal 

 products. It is only at the last ecdysis, prior to pupation, that 

 direct continuity becomes established and the contents of the 



^ A somewhat similar view has been expressed by Gatenby (1919), who, 

 along with Tothill, was not aware of Grandori's important memoir on 

 Aaputeles, 



