688 MEDICAL ENTOMOLOGY 



debris, in which the parasites are found. According to Griffiths, as 

 quoted by Newstead, the majority of the monkeys examined were infected, 

 the infection being more frequent and more intense in the older individ- 

 uals. Acid fast bacilli not the tubercle bacillus were found in the 

 debris in the cavities ; whether there is any connection between the 

 bacillus and the mite is not stated. 



Probably there are many species as yet undescribed. 



SUBFAMILY UROPODINAE 



Most of the gamasids belonging to this subfamily are found on beetles 

 and other insects. The mandibles are long and slender and end in 

 pincers ; in some species they are actually twice as long as the body of 

 the mite. The species which are found on insects are not all true 

 parasites ; many attach themselves simply in order that they may be 

 carried from one place to another. Such emigrant forms are nearly 

 always nymphs, and are attached to their carrier by means of a long 

 pedicel, said to be formed of the secretion of the glands in the region 

 of the anus ; they are known as nympha pedunculata. A few of the 

 mites of this subfamily are true parasites, and live on ants. These 

 parasitic forms never attach themselves by a pedicel. 



SUBFAMILY GAMASINAE 



This subfamily contains a large number of genera, many of the species 

 of which are closely allied to the dermanyssids. Most of them are free- 

 living, a few of the species are temporary parasites of mammals. Two 

 closely allied genera contain several species which are parasites of rats 

 and other small rodents, the blood of which they suck. Banks gives the 

 following key to the two genera Laelaps and Myonyssus : 



Anal plate small, much smaller than the median plate . . Laelaps. 

 Anal plate large, larger than the median plate .... Myonyssus. 



GENUS LAELAPS, KOCH, C. L. 



This genus contains a large number of species, among which there 

 are a few which are parasites of rodents. The scutum is armed with 

 many bristles and there are some on the margin of the ventral plates. 

 There is also a bristle at the margin of the anal plate. Three species 

 which are known from rats are distinguished by the following key given 

 by Banks : 



1 . Dorsum with numerous fine hairs ; no stout spines on coxae . stabularis. 

 Dorsum with fewer, but stouter spine-like bristles ; each coxa 

 has a stout spine . . , . . ..... . , . . 2 



