THE ACARIXA OR MITES. 



105 



becomes enormously swollen, so that it is 20 to 100 times greater than the rest of the 

 body, the whole animal appearing as a white spherical grain, \vith a tiny scar on one 

 side. The male of Pediculoides (fig. 215) has almost no abdomen at all, the body being 

 very short, and angiilate behind. The head in this genus is almost a distinct portion 

 of the body. Brucker has studied the anatomy of Pediculoides. There is a large stom- 

 ach, connecting to the mouth by a slender oesophagus; to the latter is attached a blind 

 pharynx. He found no anus (but I believe one exists in TarsoriemMs) , the intestine 

 ending blindly near the tip of the body. The genital opening is at the tip of the body; 

 above it is a short spermatheca. In the females there are a pair of air reservoirs in 

 the front part of the body; behind them are tufts of tracheae, wliich, when the female 

 becomes swollen by eggs, extend into the swollen part. 



The Tarsonemidse have not long held any one position in the system of Acarina. 

 They have been associated with Oribatidse by several writers, and Berlese has recently 



Fig. 2\%.— Pediculoides vcntricosus: Gravid female. ^i^. 217 .—S iter optes carnea and 



(Adapted from Brucker.) claw. (Original.) 



elevated the family into one of the principal groups (Heterostigmata) of the order. 

 The dimorphism in certain forms seems to suggest affinity to the Tyroglypliidse. The 

 family was united to the Cheyletidae by Trouessart, and some have followed him, 

 but most later authors consider it distinct therefrom and more alUed to the Tyro- 

 glyphidae. Oudemans has elevated it into an order under the name Trachelostig- 

 mata, and a few other acarologists follow liim. In any location it is an isolated 

 gi'oup. The family can be di\ided into two subfamilies, as follows:. 



1. Hind legs of female end in claw and sucker, in male hind legs shorter than 



third pair Pediculoidin^. 



Hind legs of female end in long hairs, in male hind legs about as long as third 



pair Tarsonemin^, 



In the Pediculoidinse are two very distinct genera; others have been made by 

 subdividing Pediculoides. 



1. Mouth parts terminal and distinct Pediculoides. 



Mouth parts hidden by a cephalic process Pigmeophorus. 



