12 Trans. Acad. Sci. of St. Louis. 



FuKTHEK Notes Eegaeding the Separate Families. 



EupoDiDAE. — This Is a small family of mites which live in dark, damp 

 places. They are predaceous and of very agile movements. 



Bdellidae. — A small family of mites of medium size. They live among 

 dead leaves and rubbish, but may be found on trees under bark. 

 All are predaceous. The mouth-parts are very large, the palpi may 

 be raptorial. 



Chetletiuae. — The genus Chcylctus is free and predaceous, and its 

 members are found under dead vegetation and under dead bark, 

 etc. Cheyletiella Is found upon furred animals, but It Is doubtful 

 if It lives at all from their tissues, but rather, simply preys upon 

 other parasites present. The parasitic genera are found upon both 

 birds and mammals. 



Caecltlidae. — Only a few forms are included in this family, and little 

 or nothing is known of their habits. They are found In moss and 

 rubbish where there is plenty of moisture. 



Tetraxychidae. — All the members of this group are plant feeders. 

 Where the attacks of a single Individual or several generations of 

 the same species are confined to a single food plant (hence host 

 plant) the species is called parasitic. In several cases there Is a 

 strong tendency for individuals to attack a single plant, yet they 

 may leave the same; these species may be called semi-parasitic. 



Ebythraeidae. — The two free genera include predaceous forms which 

 run about plants. The parasitic genus includes forms parasitic on 

 reptiles. 



RHYNCHOLOPHinAE. — Rather large acarlds, the adults of which are found 

 running over the leaves of various plants and the bark of trees. 

 The adults are predaceous. 



Tkombidiidae. — Some of the mature forms of this group constitute the 

 largest known free-living Acarlna. Although the larvae are para- 

 sitic, the mature forms are predaceous. 



Hydrachmdae. — The largest family of the order. They are aquatic, and 

 with but few exceptions, are free in the adult state. The larvae 

 are parasitic on aquatic insects. 



Halacaridae. — Includes marine forms. All the adults are free and feed 

 upon minute vegetation. Some cf the larvae are free and some 

 are parasitic. 



IxoDiDAE. — Includes most of the ticks. All are parasitic, but usually 

 leave their hosts in order to molt. They are haematophagous, and 

 do not show nearly as great a stage of degeneration as some of the 

 other parasitic groups. 



Abgasidae. — A very small family, including some forms of ticks which 

 have not degenerated as much as the true ticks. They are noc- 

 turnal, haematophagous parasites. 



