246 



MITES AND TICKS. 



itch-mite (enlarged SO times). 

 (Lower view of female.) 



specimens with benzine. A large number of mites living parasitically upon 

 mammals — such as the mouse-mite (Myocoptes) — and birds also belong to the 

 Sarcoptidce ; but the only species that we have space to mention is the itch-mite 

 (Sarcoptes scab lei), which gives rise to the disease known as scabies. This 

 malady and the irritation accompanying it are caused by 

 the mite excavating tunnels under 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. 



Worm-Like In the group Vermiformia the elongate 



Group. abdomen is divided into a multitude of small 

 rings. There are no e\ r es and no tracheae. The suborder 

 contain only the two families Demodicidce and Pfoytoptidaz. 

 In the former the adult is provided with four pairs of short 

 three -jointed legs ; the mandibles are styliform, and the 

 palpi formed of four segments, each armed with a claw. The family is represented 

 by Demodex folliculorum, a minute mite less than jfo 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 forepart 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 tilicB. 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 seem 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 affinities are 

 unknown. The first of these are the Tardigrada, or bear-animalcules, which com- 

 prise microscopical animals living in damp sandy and mossy spots. The body is long 



Demodex folliculorum (enlarged 600 times 



Aberrant Types. 



