110 



DR. A. C. OUDEMANS — A SHORT SURVEY OF 



females between the sternal and genital (striated) shield (figs. 5 & 6). The 

 sperm is packed in a minute vesicle or spermatophore in the shape o£ an old- 

 fashioned purse. The male effects impregnation by grasping one of these 

 spermatophores with his own mandibles and placing it within the genital 

 aperture of the female. 



It is superfluous to mention here the families into which the group is 

 divided. We need only draw attention to the L^lapid^e, many species of 

 which are our friends or auxiliaries, as they devour all kinds of mites which are 

 noxious to cultivated plants (fig. 5) ; and to the Dermonyssid^, many species 

 of which infest our birds (fig. 6) and occasionally even mankind. 



The Mesostigmata are easily collected by sieving decaying leaves, by 

 drawing a net over low herbage or grass, by brushing dead birds and small 

 mammals, by inspecting with a magnifying glass the underside of leaves, 

 the bark of trees, etc. They should be picked up with a soft moistened 

 paint-brush and should be jn-eserved in alcohol. 



(5) Paeastigmata, or Uropodoidea (Stalked Mites), are always smaller 

 than one millimetre, almost circular or oval in shape, light to dark brown in 

 colour, ventrally almost flat, dorsally usually convex, and slow in their 

 movements. — Their stigmata lie between the second and third pairs of legs, 



Fig. 7. — TJropoda iifricana, Oudms. ; deiitonyniph. — To the left : dorsal side, tlirougli which 

 the extreniel}^ long mandibles are discernible (only one is delineated). To the right: 

 ventral side ;^ S = stigma ; Pe = peritrenia ; Pi = leg-pits j St = stalk. Above: man- 

 dible. — Original. — Useful species. 



and a long serpentine air-containing peritrema is always present. The 

 dorsal view in the accompanying figure of Uropoda africana (fig. 7) indicates 

 the position of one of the very long exsertile mandibles, when completely 

 withdrawn within the body. These nipper-like mandibles enable the mites to 

 seize their prey at some distance. Their food consists usually of other mites 



