PARASITOLOGY. 65 



Sulphur is not essential when nicotine is used. The 

 nicotine must be at least .07%. 



^EMODECIDAE. 



The sub-family Demodecidae includes a group of 

 parasites that live in the hair and sebaceous follicles 

 of the skin and produce cuticular pustules. They are 

 placed under one genus, — Demodex (worm-like) and 

 one species,— Folliculorum (follicle). 



Gejieral Descriptio7i. — Under a low-power micro- 

 scope the parasite has a general outline similar in 

 shape to an oat grain. The head part is broad and 

 is provided with a stylet or lancet-piece arranged at 

 the anterior extremity. The thorax is not distinctly 

 separated from the abdomen. The larva is provided 

 with three pair of legs, the adult with four. Each 

 leg is made up of three short segments, the last 

 one being very short and provided with two booklets 

 or claws. 



Life History .—T\ie life history is similar to that of 

 the sub-family Sarcoptidae. The ova are laid in the 

 pustule. The newly hatched larvae are asexual and 

 are provided with three pair of legs which are mere 

 tubercles. After moulting the larvae are observed 



