Mesostigmata 83 



3. Euhuemogamasus Ewing, 1933 



Type. Euhaemogamasus onychomydis Ewing, 1933 



4. Ischyropoda Keegan, 1951 



Type. Ischyropoda spiniger Keegan, 1951 



Discussion: Keegan 1950 removed Acanthochela from the family 

 because he could not determine the nature of the chelicerae or tectum 

 on the type material in the United States National Museum. Examina- 

 tion of the material with a phase-conlrast microscope reveals that the 

 tectum and chelicerae are typical of the Haemogamasidae. 



Haemogamasids are parasitic on small mammals all over the world. 

 They frequently spend most of their time in nests and only get on the 

 host to feed. They have a typical life cycle and pass through a larval 

 and two nymphal stages before becoming adults. The fact that these 

 mites are common on small mammals suggests that they may be im- 

 portant in the transmission of plague, typhus, tularemia, and perhaps 

 other diseases. Investigation of their disease-carrying potentialities is 

 yet to be undertaken. 



References: 



Ewing, H. E. 1933. New genera and species of parasitic mites of the super- 

 family Parasitoidea. Proc. U.S. Nat. Mus. 82: Art. 30:1-14. 



Keegan, H. L. 1951. The mites of the subfamily Haemogamasinae (Acari: 

 Laelaptidae). Proc. U.S. Nat. Mus. 101(3275) :203-268. 



Vitzthum, H. 1930. Milben als Pesttrager? Zool. Jahrb. 60:381-428. 



Dermanyssidae Kolenati, 1859 



Figures 62 — 64 



Diagnosis: Dermanyssids are medium-sized mites. The dorsal plate 

 is either undivided in the female or is divided so that the anterior plate 

 is large and the posterior one extremely small. The ventral plates of 

 the female are typical of the suborder except that they are somewhat re- 

 duced. The sternal plate has three pairs of setae, while the metasternal 

 plates are reduced and lateral to the genital plate. The genito-ventral 

 plate is drop-shaped posteriorly. The anal plate has three characteris- 

 tic setae. In the Dermanyssidae the chelicerae may be extremely elon- 

 gated and terminate in a minute shear so that they appear to be a pair 

 of needle-like structures, or they may be more normal with merely 

 reduced chelae. Tritosternum is present. All legs have pretarsi, carun- 

 cles, and claws. 



