Trombidiformes 



187 



are three- to five-segmented. The digitus mobihs of chelicerae is sharp, 

 for piercing, and extends beyond the digitus fixus. All tarsi have claws 

 and haired pulvillus. Two pairs of genital suckers are present. 



Genera: 



1. Ereynetes Berlese, 1883 (= Micrereunetes Berlese, 1923) 

 Type. Ereynetes berlesei Oudemans, 1928 



2. Opsereynetes ThoT, 1932 

 Type. Opsereynetes norvegicus Thor, 1932 



3. Riccardoella Berlese, 1923 

 Type. Acarus limacum Schrank, 1781 



Discussion: These mites are 

 known from Europe, North Amer- 

 ica, Java, Sumatra, and Japan and 

 are likely to be found wherever 

 careful collecting is made. They are 

 moss-lichen and sometimes leaf in- 

 habitants and appear to be preda- 

 ceous. The species, Riccardoella 

 limacum (Schrank) is to be found 

 in Europe and North America on 

 the common snail. Helix pomata L. 

 This mite is at times abundant on 

 the slimy parts of the snail but ap- 

 parently does not cause its host any 

 harm. Turk and Phillips 1946 have 

 studied the slug mite and have 

 worked out the life history as fol- 

 lows. Eggs are laid in the mucus of 

 the mantle cavity of the snail. The 

 egg hatches into a six-legged larva 

 which lacks the posterior pair of ab- 

 dominal sensory setae and the geni- 

 tal suckers. The proto- and deutonymphs resemble the adults. However, 

 these workers state that this species exhibits neotony in that the deu- 

 tonymphal stage (nympha generans) contains the eggs, whereas the 

 adults examined were never found with well-developed ova. The fe- 

 male deutonymph is either viviparous or ovoviviparous. The mites do 

 not spend the entire time on the snail, but run along the ground and 



Figure 127 Opsereynetes rohustiis 

 Baker. Dorsum of female. 



