MICRO TROMBIDI UM 



727 



and other vegetables. After some growth the nymphs seek shelter 

 under the earth and become pupae. 



The pupa is formed from the elongated body of the nymph, inside 

 which the adult form develops, and which in a few days emerges. 



The imago is at first without sexual organs, which begin to de- 

 velop. Meanwhile the adult grows and undergoes more than one 

 ecdysis, and in about ten weeks arrives at sexual maturity. 



The eggs are laid singly in earth, but oviposition has not been 

 observed, and the earliest egg known is the dentovum, o-2i-o-24 x 

 0-17-0 -22 mm., inside which the chorion, having split the pale 

 vitelline membrane, could be seen containing the red akamushi, 

 which hatched out after three weeks' incubation. 



Microtrombidium wichmanni Oudemans, 1905. 

 Its larva attacks man and animals in Celebes. i 



Microtrombidium vandersandei Oudemans, 1905. 

 Synonym, — Microtrombidium Van der Sander. 



The larva of this Trombidium occurs in New Guinea, and attacks man 

 and animals. Its local name is ' Gonone.' 



Metatrombidium Oudemans, 1909. 



Metatrombidium poriceps Heim and Oudemans, 1904, has been found on 

 fowls, dogs, and men. 



Family Tetranychid^. 



Trombidoidea with first and second pairs of legs without spines ; skin with 

 few shields ; palpi not much thickened on base, moving vertically ; eyes usually 

 present. First pair of legs do not end in long hairs. Coxae more or less in 

 two groups. Body with fewer longer hairs. No dorsal groove; often spinning 

 threads; tarsi never swollen. Mandibles styliform. 



Genus Tetranychus Dufour. 



Definition. — Tetranychidae without cephalothoracic tubercles. Few legs, 

 slightly longer than body, which is not twice as long as broad. Legs slender. 

 Integument not tessellated dorsally. Palpi ending in a distinct thumb. 



Tetranychus molestissimus Weyenbergh, 1886. 

 This mite is found in the Argentine and Uruguay. It is small and of red 

 colour, living in a web on the inferior surface of the leaves of Xanthum macro- 

 carpum. From December to February it attacks mammals and man, thrust- 

 ing its hypostome into the skin and causing severe itching. Another species — 

 T. telarius (var. russeolus) L., 1758 — may attack human beings. 



Family CHEYLETiDiE. 



Trombidoidea without spinous processes on the legs ; skin with few if any 

 shields; palpi much thickened at the base, moving laterally; last joint often 

 with two pectinate bristles without eyes. First leg ending in several long 

 hairs. 



Cheyletus Latreille, 1796. 

 These are very small mites, distinguished by having enormous palpi, with 

 pectinate bristles. Cheyletus eruditus has been described in the external 

 auditory meatus of a man. 



