164 Transactions of the Society. 



of these Acari in large numbers must set up a certain amount of 

 irritation likely to predispose to pulmonary disease, and may be 

 a factor, if not the actual reason, for the marked susceptibility of 

 Macacus Monkeys to such diseases. Infestation probably takes 

 place early in life, as many of the monkeys examined were young 

 individuals, perhaps half grown. How the Acari find entrance to 

 the lung in the first instance has yet to be established, but 

 probably infestation takes place via the nasal passages or mouth. 

 Once established in the lung, however, breeding takes place, and 

 apparently the whole life -cycle can be passed through in this 

 environment, as I have found young and advanced larv?e, nymphs, 

 and adults present in the lung. The number of Acari present in 

 the vesicles varies, ranging from a single individual to twelve or 

 fourteen. Males appear to be few in number as compared with 

 females. 



The Acari in the larval, nymph, and adult stages of their 

 existence are semi-opaque, ashy-white in colour, the mid-intestine 

 and diverticulpe showing through the semi-transparent surface of 

 the dorsal skin in pale opaque, cream-coloured lines. The 

 epidermis is soft and easily ruptured, therefore considerable care 

 is necessary in handling and mounting these Acarids for micro- 

 scopic examination. 



The larva is six-legged, short and oval in shape, averaging ^^Q-th 

 of an inch in length of body, yJo^^^ ^^ ^^^ ^^^^^ across the thorax, 

 and g^th of an inch across the greatest width of abdomen. The 

 first pair of legs average y^gth of an inch in length, and the 

 second ^jfi^ and third pair j^th of an inch. The legs have a few 

 stout hairs, and are cylindrical and tapering to the slender foot. 

 The tarsus is very slender, with equal curved claws, and well- 

 developed pulvillus, which extends between and beyond the claws. 

 The palps are tapering, and appear more prominent and, in 

 comparison, slightly longer than in the adult, each palp bearing a 

 long stout terminal hair. The mandibles are pointed, and straight- 

 edged on their inner surface, like the blade of a knife. 



The nymph and adult closely resemble each other in size and 

 shape, the most distinctive feature in the nymph being the absence 

 of the external genital pore. The palpi are short, composed of 

 three segments, and crowned with a minute apical hair. The 

 body is oblong, broader at the abdominal extremity, narrower 

 towards the thorax. Average length of body of adult female, ^^th 

 of an inch ; average width across thorax, -^\h of an inch ; average 

 across greatest width of abdomen, ^W\ of an inch. The genital 

 pore is situated centrally on the anterior part of the ventral surface 

 of the abdomen, as a transverse oblong slit with a slightly 

 thickened rim. The mandibles in the adult are chelate, have 

 slender curved points, and rest witliin a transparent sheath. The 

 legs are cylindrical and tapering, each segment bearing a few hairs. 



