20 



REPORT 108, U. S. DEPARTMENT OF AGRICULTURE. 



Fig. 8.— Venter of an 

 eupodid. (Author's 

 illustration.) 



Superfamily EUPODOIDEA. 



Family EUPODID^. 



The Eiipodidae is a small family of small mites, several species of which are among 

 our most common acarians. They are soft-bodied, delicate mites, with moderately 

 long to very long legs. The body shows more or less distinctly the di\ision into 

 cephalothorax and abdomen; the former usually bears an 

 eye each side; the latter carries a few simple hairs. The 

 palpi are short and simple, four-jointed, and with only a 

 few hairs. The mandibles are rather small, but distinctly 

 chelate; in one genus they are very large. The legs are 

 six or seven jointed and terminate in two simple claws, 

 and often with a median plumose pulvillus. The venter 

 (fig. 8) has the usual openings, but in Notophallus the anal 

 aperture is on the dorsum of the abdomen. In this genus 

 there are a pair of suckers each side of the genital open- 

 ing, apparently used by the mite to hold to smooth 

 surfaces. These mites can run rapidly, and Eupodes can 

 make considerable leaps. Most of them occur on the 

 ground, but some are found on the leaves of trees. Many 

 are predacious and feed on various small insects or in- 

 sect eggs. They seem to delight in cold, damp places, and 

 can be found in winter still active among and under fallen 

 leaves. They are among the most common acarians 

 in high latitudes, and are also frequent in caves, both 

 of this country and of Europe, where their simple 

 and primitive structure is well suited to the conditions. 

 Their internal anatomy has been investigated by Nordenskiold, who finds that 

 Rhagidia is among the most primitive of the Trombidioidea. The oesophagus, 

 which opens near the tip of the labium or under lip, is very slender, and after 

 passing through the large "brain," enters a very large stomach. From the upper 

 part of this arises the intestine, which soon expands 

 into a large colon, opening at the tip of the body. 

 The eggs, as far as known, are laid upon the sur- 

 face frequented by the adult. The larvae resem- 

 ble the parent, while the nymph differs only in 

 size. There is no sexual dimorphism. Most of the 

 common species vary a great deal in markings, the 

 consequence being that Koch described each of the 

 common European species under many different 

 names, several having from 10 to 20 s>Tionyms. 

 Our forms have been collected only in the Eastern 

 States. Their small size, soft body, and the rapid- 

 ity of their motions makes it a very difficult matter 

 to secure specimens in good condition for study; a 

 toothpick dipped in glycerine is most useful for this 

 purpose. 



Two or throe genera arc sufficiently distinct from all others to form a subfamily, dis- 

 tinguished as follows: 



1. Tliree suckers on each side of the genital aperture; a pair of submedian 

 Honnory hairs on the ceplialothorax ; abdomen more distinctly seg- 

 mented ALICHIN.fi. 



But two suckers each side of the gonitiil ap>erture; no submedian sensory hairs 



on the cepluilothorax; abdomen only indiatinctly segmented Eupodl\/E. 



Fig. 9. — Alichus roscw. 

 (Original.) 



