338 ARACHNIDES, 



FAMILY III. 

 HOLETRA. 



The trunk and abdomen are here united in one mass, under 3 

 common epidermis, or at most, the thorax is divided by a strangu- 

 lation, and the abdomen, in some, merely exhibits an appearance 

 of annuh, formed by the plicae of the abdomen. 



The anterior extremity of their body frequently projects in the 

 form of a snout or rostrum; most of them have eight legs, and the 

 remainder six. 



This family consists of two tribes. In the first or the Phalatj- 

 GiTA, Lat., we observe very apparent chelicerse which either project 

 in front of the trunk, or are inferior, and always terminating in a 

 didactyle forceps, preceded by one or two joints. 



They have two filiform palpi, composed of five joints, the last of 

 which is terminated by a small nail; two distinct eyes; two jaws 

 formed by the prolongation of the radical joint of the palpi, and 

 frequently four more, which are also a mere dilatation of the hip of 

 the two first pairs of legs. The body is oval or rounded, and co- 

 vered, the trunk at least, with a firmer skin; there is also an appear- 

 ance of annulior plicae on the abdomen. The legs, of which there 

 are always eight, are long, and distinctly divided, like those of In- 

 sects. At the origin of the two posterior legs, at least in several 

 — Phalangium — are two stigmata, one on each side, but hidden by 

 their hips. 



Most of them live on the ground, at the foot of trees, and on 

 plants, and are very active; others conceal themselves under stones 

 and in moss. 



Phalangium, Lin., Fab. 

 The chelicerjc projecting-, much shorter than the body; eyes placed on a 

 common tubercle. Their legs are very long and slender, and when de- 

 tached from the body show signs of irritability for a few moments. 

 There are some other genera, viz. Siro, Macrocheles and Trogulus. 



In the second tribe of the Holetra, that of the Acarides, we 

 sometimes find chelicerag, but they are simply formed of a single 

 forceps, either didactyle or monodactyle, and are hidden in a sternal 

 lip; sometimes there is a sucker formed of united lancets; or finally 



