46 PARASITOLOGY. 



Gamasidae and Trombidiidae, to which belong 

 species of parasites infesting birds and small ani- 

 mals. (The chig'ger belongs to the latter family. 



Sarcoptidae (Sarco — flesh ; kopto^ — to cut.) This 

 sub-ifamily is divided into three important genera/ 

 producing scabies in all animals. It includes the air- 

 sac mite. 



Demodecidae include the parasites that produce 

 follicular or red mange. 



Argasidae and Ixodidae include the ticks. 



In these parasites the divisions of head, thorax and 

 abdomen are not distinctly marked, macroscopically. 

 They are all blood-suckers. The head is provided 

 with a stylet for piercing the skin and sucking the 

 blood. The piercing mandibles are surrounded by 

 two palpi. The eyes are small or wanting. The 

 larva is provided with three pair of legs, the adult 

 with four. The free extremity of the last segment 

 is provided with a booklet, ambulacrum or pulvillum, 

 which aids the parasite in holding on to its host. 



ACARIASIS. 



This is a condition of an animal being infested 

 with some species of parasites belonging to the order 

 Acarina. There are two kinds of Acariasis, viz : 

 Psoric and non-psoric. 



Psoric Acariasis is a condition in which the para- 

 sites produce scab ; infested by species of the sub- 

 families Sarcoptidae and Demodecidae. 



Non=Psoric Acariasis is a condition in which the 

 parasite does not produce scab ; infested by species 

 of the families Gamasidae, Trombidiidae, Argasidae 

 and Ixodidae. 



