TRUE GUESTS, ECTO- AND ENTOPARASITES. 4 J 7 



Janet calls attention to two other Gamasicls, Uropoda oralis (Fig. 

 247, A) and Urodiscclla [>hiloctcna (Fig. 247, B). The former 

 attaches itself by means of a glue-like secretion to the legs of ants, 

 the latter clings to the comb of the strigil by means of one of its 

 fore legs. This species evidently feeds on the dirt which is scraped 

 by the ant from its body and appendages. A similar mite is some- 

 times found attached to the spurs on the legs of our American 

 carpenter ant (Camponotus pcnnsylvanicus). Still another Gamasid, 

 Oolfflaps oopliilus, has been described by Wasmann. It is found on 

 the eggs and packets of very young larvie of Formica sanguined and 

 rufibarbis and lives on the salivary secretion with which the ants coat 

 their young progeny. Many of the mites found attached to adult ants 

 probably feed on the same substance. 



Wasmann (1897?) has also published some observations on a Sar- 

 coptid mite (Tyroyly pints ivasiiianni) which lives in the nests of F. 

 sanguined and, in the adult, nymphal and larval forms, feeds on dead 

 ants. At times, however, its hypopi become exceedingly numerous 

 and cover the bodies of the living ants in masses. These hypopi always 

 orient themselves with their heads towards the distal end of the appen- 

 dage or part of the body on which they are resting. They seem to 

 take no nourishment, but their great numbers impede the ants' move- 

 ments and eventually kill them. 



Some of the beetles of the family Thorictidse, comprising the 

 single genus Thorictus of the Mediterranean region, must also be 

 included among the ectoparasites, if we accept Wasmann's account of 

 their habits (18980, 1898/7). These are small, subtriangular, reddish 

 brown creatures, with tufts of golden trichomes at the posterolateral 

 corners of the prothorax. Several of the species, like the myrme- 

 cophilous Histeridae, seem to live on dead ants, but others (T. -for ell 

 and pauciscta) are regularly found, as Forel (18940) first observed, 

 attached by means of their bidentate mandibles to the antennal scapes 

 of Myrmecocystus workers. The host of T. forcli is M. mcgalocola, 

 that of pauciseta, M. desertonun. The prothorax of the beetle is pro- 

 vided with a groove or depression to fit the scape, towards the distal 

 end of which the beetle's head is always directed (Fig. 248). In 

 this position the insect may remain for weeks in spite of all the efforts 

 of the ant to dislodge it. Escherich (18980 found that the beetle is 

 frequently licked and that it sometimes attaches itself to the legs as 

 well as to the antenna?. Wasmann maintains that it punctures the 

 scape and sucks the blood of the ant and that Thorictus is therefore 

 both an ectoparasite and a symphile. Other species of the genus seem 

 not to have this habit of clinging to the ants. Mr. Walter Granger 



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