TROMBIDIID^E 



485 



Family. Trombidiidae (Running Mites). 



Soft-skinned Acarina with tracheae and with two eyes, usually pedunculated ; they 

 are often brightly coloured ; cheliceras lancet- or claw-shaped ; pedipalpi claw-like ; 

 legs composed of six segments, with suctorial discs between the terminal ungues. 1 

 Larvae six-legged. To the latter belong the larvae of several species of Trombidium 

 such as : 



Genus. Trombidium, Latreille (and Leptus). 



Leptus autumnalis, Shaw, 1790. 



Leptus occur as parasites in the human skin and cause a cutaneous 

 disease known as autumn erythema, and produce a very unpleasant 

 sensation on account of the trouble- r- 



some itching ; in children it is very 

 often accompanied by fever. 2 



Formerly these mites were considered 

 adult forms, but when they were recog- 

 nized as mite larvae they were taken 

 for those of the spider-mite (Tetranychus 

 telarius) ; the investigations of Hanstein, 

 however, showed this to be a mistake. 



FlG. 349. Leptus autumnalis, with so-called 

 sucking proboscis. Enlarged. (After Gudden.) 



FIG. 350. Leptus autumnalis : the 

 so-called proboscis is formed around 

 the hypopharynx sunk into the skin. 

 100/1. (After Trouessart.) 



When Henking first investigated the development of Trombidium fuliginosum, 

 parasitic in the larval stage on vine-fretters, he demonstrated the occurrence of a 

 form very similar to Leptus autumnalis, and the "autumn, grass, or gooseberry" 

 louse was commonly designated the Trombidium larva. Even before Henking's 

 work it had been described by Megnin as the larva of Trombiditim holosericeum, a 

 red-coloured species, frequently occurring in spring and summer on the ground, trees, 

 etc. This assumption, however, as Moniez was the first to explain, is not correct ; 



1 [Some have seven segments to the legs. F. V. T.] 



2 [This minute parasite is especially obnoxious in barley fields. In walking over barley 

 stubble one is sure to be attacked by this Acarus in many districts. Trombidium is often very 

 prevalent in gardens, especially along rows of peas, and in spring they may be found on fruit 

 trees and bushes. Nut-pickers are frequently attacked by Leptus, and also pickers in other 

 fruit plantations. It is often called the harvest mite. F. V. T.] 



