The Zoologist — June, 1866, 237 



only enabled to prepare a specimen whenever I like, but also to supply 

 some facts as to its life-history which could only have been obtained 

 by keeping it for some considerable lime in a living state. 

 ' The question of food puzzled me for some time, as I naturally con- 

 fined myself to obtaining supplies from the locality where I found the 

 Acarus, but a part of the cocoon, the eggs of a spider, and their first 

 cast skins, were all alike refused. It was only as a last resource and 

 judging from the remarkable size of its falces, together with its pecu- 

 liar movements, that I gave it some living Acari of a different species; 

 these I soon saw were quickly seized — the disappearance of my colonies 

 of Acari which I have mentioned was at once explained, and I 

 continued to supply my new specimen with food, hoping it would turn 

 out to be an impregnated female. 



In a few days it laid some eggs, and these duly hatched, and many 

 subsequent generations have been produced by them. I am now able 

 to supply the following facts connected with this Acarus, which I 

 believe are new. 



The eggs, as compared with those laid^by other species of Acari with 

 which I am acquainted, are rather small in proportion to the parent; 

 they are of a bluish white colour, transparent, and adhere to the 

 substance they are laid upon by a short thread at one extremity. At 

 the age of two or three days in summer time, the young may easily be 

 detected inside the egg, which hatches, according to ray memoranda, in 

 five, six, or seven days from the time it was laid ; the variation in this 

 and other periods of development being due, I believe, in great 

 measure to the temperature of the atmosphere. 



The young as it comes from the egg has only six legs ; it is white, 

 perfectly transparent, and very active, wandering about in every 

 direction. At the age of seven days it casts a skin, and then acquires 

 eight legs ; at a further interval of seven or eight days it casts a second 

 skin, and then arrives at maturity ; before each of tliese raoullings the 

 individual remains sometimes for one or two days perfectly stationary 

 and apparently dead; I mention this circumstance so that any one 

 who likes to repeat these experiments may not disturb the Acarus in 

 this important operation. 



This Acarus soon after arriving at maturity assumes a yellowish green 

 colour, and I will endeavour to describe some of its more remarkable 

 features at this stage of its life. 



That which strikes one at first sight is the size of the falces, for I 

 presume they cannot be correctly termed mandibles; they are largely 



