16 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



vol.. XXVIII. 



The iiitonml anatomy has been studied by ))oth Karpolles and 

 Michael. It is peculiar in several respects. There is a large sac or 

 diverticulum connected to the (esophagus above. ]VIichael has termed 

 it the receptaoiJuin cih't , and believes its purpose is to store the food 

 for a short time. The ventriculus ends blindly; there being no com- 

 nuuiication to the anus. There are three pairs of 

 glands in the anterior part of the body, besides 

 one large median gland. One pair opens at the 

 l)ase of the mandibles and their function is un- 

 known. Two pairs open into a common duct 

 which leads to the mouth; they are probably 

 salivary glands. The supra and sub-oesophageal 

 ganglia are more distinctly separated than in 

 other mites that have been examined. The phar- 

 yngeal nerve (which in other mites is single) 

 in Bdelhi is split in two parts. The male organs 

 are remarkable for possessing two single and one 

 pair of accessory glands, whose function is little 

 undei'stood. In the female there is but one ovi- 

 duct. 



Mr. Triigardh has figured the egg of B. arctlai ; 

 it is nearly spherical, and with a lumiber of long- 

 spines scattered over the surface. The larva and 

 nym})h have nuich resemblance to the adult. 

 They are never parasitic, and there is no sexual 

 dimorphism. 



The species are usually red in color, but some 

 are blackish. They are predaceous in habit and 

 wander about in search of food — any small creature they can find. 

 The palpi serve as tactile organs in most genera, but in /Seines they 

 are used to capture and hold the prey. These mites can run quite fast, 

 and move backward as well as forward. Several species are known 

 from the Arctic regions. Four genera have been recognized in this 

 country, and one more (Sr/'/-i/l(i) is known in Europe. They may be 

 separated by the following table: 



1. Mandibles chelate; two eyes each side; iial])i geniculate, and ending bluntly with 



two or more long l)ristles 2 



Mandil)les ending in one claw; no eyes, or only one each side; palpi not geni- 

 culate, and ending in a claw 3 



2. No median eye on front margin of cephalothorax; tip of tarsus with one or two 



plumose hairs each side Bdella 



A median eye on front of (•e])halothorax; tip of tarsus without plumose bristles. 



Cilia 



3. Palpi of three joints, and without spine-like bristles, one eye each side on ceph- 



alothorax Eupalus 



Palpi of five joints; and with sjiine-like ])ristles; no eyes Scirus 



Fig. 1 1.— Bdella tene].l.\. 



