THE FAUNA OF BOULDER COUNTY 25 1 



Family GEOPHILIDjE 

 Small thread-like centipedes; pairs of legs never less than 30. 

 One or more undetermined species occur in our fauna. Geophilus umbraticus 

 McNeill is recorded from West Cliff, Colorado. 



Class ARACHNIDA 

 Order ACARINA 



The mites and ticks. Although quite easily recognized at sight, it is not so easy 

 to give definite characters whereby to distinguish a mite from other Arachnids. 

 The abdomen and cephalothorax are broadly united to each other, and often there 

 is no distinction between these parts. Usually there is no trace of segmentation, 

 but in some forms it is quite distinct. Eyes are often present but rarely only a 

 median pair as we find in Phalangids and Solpugids. The mouth segments have 

 united to form a beak, rostrum or capitulum. Commonly the larva at birth has 

 but three pairs of legs, and obtains the fourth pair only after a molt and metamor- 

 phosis. In the Eriophyidae, however, there are but two pairs of legs in both adult 

 and young, and in Pteroptus the young have eight legs at birth. (N. Banks, 

 Proc. U.S. Nat. Museum, XXVIII, p. 2.) 



SUPERFAMILY DeSMODICOLDEA 

 Abdomen annulate, prolonged behind; very minute forms. 

 Family ERIOPHYID-S 



With but four legs, of five joints each; living on plants, often in galls (Banks). 



(98) Eriophyes Siebold. We have several gall-forming species; one has been 

 described, E. rhoinus Cockerell, on Rhus glabra cismontana, producing gall-masses 

 consisting of modified branches with multitudes of small, distorted leaves. 



(99) Cecidoba Banks. Producing galls on leaves of Salix. C. salicicola Banks.* 

 Ward is the type-locality: I have since found the species on the University campus 

 at Boulder. 



Superfamily Ixodoidea 



Large forms, commonly known as ticks. 



Family IXODIDiE 

 Scutum present; mouth-parts of adult prominent from above; pulvillus to tarsus 

 of both adults and young; stigmal plate behind fourth coxae (Banks). 

 (100) Dermacentor Koch. Eyes present; dorsal surface of capitulum nearly 

 rectangular. D. venustus Banks. The common wood-tick of our vicinity, formerly 

 confused with D. occidentalis . 



Superfamily Oribatoidea 



Body usually coriaceous, with few hairs; with a specialized seta or bristle arising 

 from a pore near each posterior corner of the cephalothorax; no eyes; mouth- 

 parts and palpi very small; never parasitic (Banks). 



