488 THE ANIMAL PARASITES OF MAN 



Family. Tetranychidae (Spinning Mites). 



These have tracheae and eyes ; the palpi are composed of four segments, of 

 which the last but one has a powerful claw. The legs have six segments with sucker 

 discs between the claws. 



[The red spiders or spinning mites (Tetranychi) are usually placed 

 in the family Trombidiidce. F. V. T.] 



Genus. Tetranychus, Dufour. 

 Tetranychus molestissimus, Weyenbergh, I886. 1 



Found in Argentine and Uruguay on the under surface of the 

 leaves of Xanthium macrocarpum ; it attacks mammals and men, 

 producing severe itching, accompanied by fever in the latter. 



It has been asserted by Haller 

 that the CAPE AILMENT (Port Natal 

 sickness) is caused by mites, but this 

 statement has been contested. 



Tetranychus telarius, L., i758, 2 

 var. russeolus, Koch. 



This common spinning mite like- 

 wise attacks human beings, but the 

 papules produced by it very soon 

 disappear. 



Family. Tarsonemidae. 



A family distinguished by complete 

 sexual dimorphism, the species of which are 

 provided with tracheae ; the legs have five 

 segments ; the terminal segments of the 

 front pair of legs of both sexes possess a 



FIG. ^z.Jetranychus telarius var. rus- claw; the terminal segment of the posterior 



seolus, Koch. Enlarged. (After Artault.) pair of legs of the male likewise has a claw. 



In the female this pair of legs, like the 



second and third pairs of both sexes, is provided with two hooklets and a sucking 



disc. The cuticle of the body on the back is " annulated." 



[This family of small transparent mites live normally as plant 

 parasites. The last two pairs of legs are widely separated from the 

 two front pairs. F. V. T.] 



1 [This species is also known as Bicho Colorado. It spins a web under the lower surface 

 of the leaves, and it is only from December to February that it attacks warm-blooded animals 

 and man. F. V. T.] 



2 [There is something wrong here, probably in the identification. T. telarius is purely 

 a plant-feeder, and it is extremely unlikely a variety would attack man. Anyhow, it will not 

 do so in Great Britain. F. V. T.] 



