PARASITES OF THE TETTIGID^. 41 



If an animal is subject to the parasitic attacks of 

 insects, we may pretty confidently conclude that the 

 HymeDopteroiis order will furnish something in the 

 list. Such an insect has been the particular study of 

 Dr. Josef Mik, of Vienna, who, in 1882, wrote an 

 interesting memoir on the biology of Gonatopus pilosus 

 of Thoms., which, in the larval condition, clings to the 

 abdomen or thorax of several Acocephali and Delto- 

 cephali. In places where such insects are common, 

 individuals may often be found having a black or 

 brownish excrescence, as large as a millet-seed, gene- 

 rally protruding from the first abdominal ring of their 

 bodies, or adhering very strongly to the pronotum 

 close to the head. If torn away, this body has the 

 form of a hard purse-like sac, without apparent limbs 

 of any kind. Its texture is tough and chitinous, 

 smooth and shining, somewhat pear-shaped, and fur- 

 nished round one edge with a deep suture (eingeschohene 

 Schienc). (See Plate D, fig. 3). There appears to be 

 a faint indication of segmentation into rings, and, at a 

 later stage of development, there are, according to 

 Prof. Mik, obscure rudiments of a head and antennae. 



At first Prof. Mik failed to breed any living forms 

 from these sacs, for the hosts (Cicadse) soon died in 

 confinement ; but subsequently, in early September, 

 he obtained winged specimens of Deltocephali, with 

 these sacs attached, and with these insects he was 

 more fortunate. He found a quantity of prismatic 

 bodies scattered within the substance of these purses, 

 which he thought probably might be compounds of 

 uric salts. 



During an examination of these bodies, previously 

 softened by soaking in water, I (the present author) 

 could find nothing within their interior beyond a 

 quantity of undifferentiated semi-fluid matter, but with 

 no defined traces of organised limbs. The exterior 

 case, however, could be partially unravelled by needles 

 into black silk-like fibres, which extended from the 

 back towards the suture. Their general distribution 



