THE MITES AND TICKS 



3213 



Worm-Like 

 Group 



ITCH MITE (enlarged 80 



times). 

 (Lower view of female.) 



the skin. In these the eggs are laid, and hatch; and the young then start burrow- 

 ing on their own account. The burrows usually show as whitish lines on the 

 surface of the skin, and if the skin at the end of one of these lines be pricked with 

 a sharp needle, the mite may be without difficulty extracted. 

 In the group Vermiformia the elongate ab- 

 domen is divided into a multitude of small 

 rings. There are no eyes and no tracheae. 

 The suborder contain only the two families Demodicidce and 

 Phytoptidce. In the former the adult is provided with four 

 pairs of short three-jointed legs; the mandibles are styli- 

 form, and the palpi formed of four segments, each armed 

 with a claw. The family is represented by Demodex follicu- 

 lorum, a minute mite less than one-fiftieth of an inch in 

 length, living parasitically in the sebaceous sacs and hair 

 follicles of the human skin. The same or an allied species 

 has been found in the skin of a dog suffering from mange, 

 where they occurred in such quantities that thirty or forty 

 might be seen in a single drop of matter. The members of the second family, 

 commonly known as gall mites, have lost all trace of the third and fourth pairs 

 of legs; the first and second pairs only remaining and projecting from the fore part 

 of the body. These legs are long and five jointed, the mandibles are styliform, and 



the palpi tactile and united at the base. The 

 long body is furnished with symmetrically 

 arranged bristles. There are numbers of 

 species, living exclusively upon the leaves 

 of plants, to which they do much damage 

 by the excrescences or galls they form. 



Each kind of tree seems to be infested by its own special gall mite, the so-called 

 nail galls of the lime being caused by a species named Phytoptus tilice. These galls 

 take the form of more or less cylindrical pointed columns, which stand erect on the 

 upper side of the leaves. As a matter of fact, they seern to arise as an inpushing 

 of the lower surface of the leaf to form a long pouch or pocket, in which the mites 

 live. Galls of much the same structure, although differing somewhat in shape, 

 occur in the sycamore, maple, elm, and various fruit trees. Other species, like the 

 Phytoptus of the currant and the yew, attack the young buds and prevent them 

 attaining maturity. 



The mites and ticks complete the list of Arachnida; there remain, 

 however, two small and obscure groups, which have been associated 

 with the ticks, but apparently for no better reason than that their af- 

 finities are unknown. The first of these are the Tardigrada, or bear animalcules, 

 which comprise microscopical animals living in damp sandy and mossy spots. The 

 body is long and oval in shape, and possesses four pairs of bud-like unjointed ap- 

 pendages, each tipped with two claws. The last pair of legs projects from the ex- 

 treme hinder end of the body. The mouth is situated at the opposite extremity, but 

 the only trace of jaws that it presents is a pair of stylets. There appear to be no 



Demodex folltculorum (enlarged 600 times). 



Aberrant 

 Types 



