A SYNOPSIS OF AUSTliALIAN ACARINA— ItAIMiOW. 179 



distinct, and the upper part of the body is furnished with a few 

 hairs, and these are generally long. We are indebted to the 

 labours of Michael^'' and ISalepa^''^ for our knowledge of the 

 anatomy of these animals, and to their writings students are 

 directed. The mode of coition in the Tyroglyphidce is exactly 

 similar to that of the Analgesidte. Behind the (diks there is a 

 small ojaening — the copulative aperture. In (iluciiilnKins, the 

 h}irm copalatrix projects externally into a small cone. Copu- 

 lation is not performed through the vulva, but by this special 

 opening. -^^ This opening leads to a receptaciilinii sciiiinis, which 

 connects by a small duct to the ovaries. The transformations of 

 these animals are amongst the most marvellous of the animal 

 kingdom. All Tyroglyphidte (except Carpoi/lyphiis, Robin) appear 

 to lay eggs, sometimes of a large size. The young on hatching 

 are six-legged, and after moulting obtain two more. From thence 

 they may pass on to the adult state in the normal way, but more 

 frequently they pass through what has been already referrefl to 

 as the lu/jKipial stai/c. The Hi/popiix is very distinct from the 

 octopod nymph from which it has developed. The body is liard 

 and chitinous ; there is no mouth orifice, and no distinct mt)uth 

 parts. The legs are short and ill-adapted for walking. On the 

 ventral surface at the posterior extremity there is an area distinct 

 from tlie general surface. This area is provided with sucking- 

 discs, by means of which the animal clings to the body of an 

 insect or other creature, and so the Acarid is carried about until 

 it finds a suitable locality to undergo its next great change or 

 molt, which transforms it into an octojiod nymph that will feed 

 and ultimately develop into an adult mite. Hence the hypopai 

 stage is a phase in tlie life of a Tyroglyjjhid for the purpose of 

 migration, but the causes which induce a nymph to transform to 

 the Hypopiis are not known. 



When Tyroglyphids swarm in stored foods — cereals and the 

 like — or buildings it is exceedingly difticult to combat them, since 

 as they have no traclue they are not very susceptible to fumiga- 

 tion, though some will succumb to the treatment. The writer 

 once saw a grain merchant's store in Sydney in which these little 

 wretches swarmed in countless millions, to eradicate which much 

 time and no little expense had to be devoted. 



Two indigenous species of Tyroglypliidje have been recorded 

 from Australia, but in addition to these others occur which have 

 a more or less cosmopolitan range. 



i« Michael— Journ. Quek. Club, 1879, pp. 223-230, pi. xiii. 



19 Nalepa— Sitz. K. Akad. Wicn., 1883, xc, pp. 197-228; Aim. Mac;. Nat. 



Hist., xiv., 1883, pp. 3t)9-371 (al)strac-t). 



20 Banks— Proe. U. States Nat. Musouni, xxviii., 1894, p. 79, 8U. 



