184 NATURAL HISTORY. 



which they chiefly occur are such as burrow into the ground, in Britain especially the common 

 Dung Beetles (Geotrupes) and the Humble Bees. 



Besides these well-known parasites of insects, the family includes several species which infest 

 vertebrate animals, and are sometimes great plagues. One of the best known is the "Tick" 

 (Dermanyssus avium] that infests domestic poultry, and also makes its way into pigeon-houses, and 

 even into the aviaries and cages in which small birds are kept. When numerous, these parasites 

 are often injurious and even destructive, especially when they attack small birds ; and they will 

 also transfer their operations to the bodies of human attendants on their natural victims, some- 

 times with very disagreeable results. Several other species of Dermanyssus and allied genera live 

 parasitically upon Bats, and some of these present most remarkable characters. 



FAMILY VI. IXODIDJE, Oil TICKS. 



In the Ixodidae we have another family of parasitic Mites, some of which are well known in 

 Europe under the name of Ticks, although it is in warmer climates that they most abound and attain 

 their largest size. Some of them are indeed the largest of the Acarina, reaching a length of a third of 

 an inch or more. They are more or less ovate or sometimes nearly circular in form, covered with a 

 leathery and very extensible skin, part of which may, however, be horny ; the palpi are small, seated 

 on a chin-plate ; the chelicerse are retractile and generally serrated ; the eyes are sometimes pre.seut, 

 sometimes wanting ; and the legs are similar in form, with two claws and a pad. 



The sucking apparatus of these parasites is composed of the maxillae and the chelicerse. The 

 former combine to form a sort of ring-like lower lip, from which the ligular portion extends forward 

 as a grooved piece, the convex surface of which is furnished with reversed hooklets. The chelicerse 

 work in the groove of this piece, and can be pushed forward and retracted by the action of strong 

 muscles, so as to perform the part of piercing organs, while their serrated margins assist in holding 

 the parasite firmly to its victim. The quantity of blood draw:- by these little pests from their hosts is. 

 by no means commensurate with their original size. The skin is so extensible that in many instances 

 the full parasite increases to many times its original bulk, and when the victim is attacked by many 

 such enemies at once the consequences may be serious. Although generally confined to some particular 

 species or group of animals, the Ticks occasionally get upon the bodies of men, and are then very 

 troublesome. Two species of the genus Argas (placed by many authors with the preceding family) 



are particularly noted as attacking mankind. One of these is the 

 Argas reflexus, originally a parasite upon young pigeons; the other 

 may be called the Persian Tick (Argas persicus), a species found 

 in houses in some parts of Persia, and described as producing most 

 serious effects upon those whom it attacks at night. 



Of the species of the genus Ixodes and the genera which have 

 been separated from it, many inhabit woods, forests, hedge-banks, 

 and herbage generally, and attach themselves to passing animals. 

 Tims Ixodes erinaceus, a British species, is often found on dogs, 

 foxes, hedgehogs, and cattle, and is known as the " Dog Tick ; " 

 another (Ixodes marginatu-s) is described as having swarmed in 

 IXODES FLAVOMACULATUS. such great mimbers in hay-fields as greatly to impede the operations 



of mowing and drying the grass. A few species are found on bats, 



but of those which are confined to particular animals the majority, so far as known, are parasites 

 of different kinds of reptiles, especially snakes. They generally attack these near the eye. The 

 species figured is parasitic on a West African Python. 



FAMILY VII. ACARID^E, OR TRUE MITES. 



This last group includes all the Mites that have not been cut off' from the original family Acarida? 

 to form special families, and hence its members naturally show some little divergence of character. 

 They are all minute and very lowly organised Arachnida, and their skin throughout is thiu 

 and membranous, with here and there a harder band for the support of the limbs. The chelicerse are 

 nipper-like, or pointed, and in the latter case capable of being retracted into a sheath ; there are- 

 no eyes ; and the legs are either mere stumps, or produced and terminated by an adhesive vesicle. 



