SELECTED NOTES. 297 



as these gamasids are concerned, it is a case of pure toleration on 

 the part of the ants, because when their dwelHngs are disturbed 

 they show no signs of anxiety on account of their messmates, 

 whereas their flocks of aphides which may be exposed by the 

 removal of the covering of the nests are speedily attended to and 

 carried off to places of safety in the recesses of the same. 



With the exception of occasional Oribatidce, these acarids 

 appear to belong to the family Gamasida, which is the most exten. 

 sive family, perhaps, of the Acaritm, and is considered at the same 

 time as the most highly organised. 



The family GAMASiDiE is divided into four sub-families, viz. : 

 the Fieroptifm, which are found upon bats and allied creatures, 

 such as the flying-fox, etc. 



The Derinanyssince, parasitic upon bats and birds. 



The Gamasince, which are some of them parasitic in their 

 immature stages, whilst a larger proportion are entirely free-living, 

 active, predatory creatures ; and lastly, 



UropodincB. — Of these also it may be remarked that many are 

 parasitic whilst immature, for they are frequently met with attached 

 to the legs and abdomen of insects in somewhat numerous clus- 

 ters, by what was at one time supposed to be a kind of umbilical 

 cord, and from which the family derives its name. This, again, 

 appears to be a case of semi-parasitism only, resorted to as a 

 means of conveyance to " fresh fields and pastures new," for no 

 nourishment can be obtained from the hard chitinous surfaces of 

 their temporary hosts. 



The family Gamasid.« finds its place in the order Acarina, 

 having the abdomen entirely united to and fused with the cephalo- 

 thorax, and in the sub-order Metastigmata, in which the tracheae 

 open at the posterior part of the body, at the base of the legs ; a 

 skeleton having for base a sternum or ventral plate. Rostrum with 

 free, unarmed tactile palpi ; mandibles chelate. 



The sub-family Uropodin/e is characterised by having a vent- 

 ral plate, united all round with the dorsal plate ; with excavations 

 for the legs, and perforated in front to afford passage to the mouth- 

 organs. The femurs of the first pair of legs are very much thick- 

 ened, and in a state of rest entirely cover the mouth-opening ; the 

 dorsal plate flatly arched. 



International Journal of Microscopy and Natural Science. 



Third Series. Vol, VI, u 



