. A text-book of invertebrate morphology. Invertebrates. TYPE ARACHNID A. 453 7. Order Aearina. The Aearina are for the most part small forms, many being almost microscopic, while the largest, the Ticks [Ixodes), do not when at their greatest size exceed a centimeter in length, the males being much smaller. Some forms, such as Oribates and Nothrus, live among moss and in similar situa- tions, while others, such as Hydrachma and Atax, are aquatic. Many forms are, however, parasitic either upon plants (Te- tranychus and Phytoptus) or on animals, the genus Sarcoptes being the cause of the disease
. A text-book of invertebrate morphology. Invertebrates. TYPE ARACHNID A. 453 7. Order Aearina. The Aearina are for the most part small forms, many being almost microscopic, while the largest, the Ticks [Ixodes), do not when at their greatest size exceed a centimeter in length, the males being much smaller. Some forms, such as Oribates and Nothrus, live among moss and in similar situa- tions, while others, such as Hydrachma and Atax, are aquatic. Many forms are, however, parasitic either upon plants (Te- tranychus and Phytoptus) or on animals, the genus Sarcoptes being the cause of the disease termed the Itch in man, the symptoms being produced by the Mites burrowing beneath the skin. Other forms affect various animals and birds, the genera Dermaleichvs, Analges, etc., feeding upon the feathers Fig. 308.—4,. Sarcoptes scabiei; B, Demodex Wright). (after Csokok from of various birds, while others, such as Demodex (Fig. 208, B), live in the hair-follicles or sebaceous glands of the skin, pro- ducing acnelike pustules. The larvae of many forms which are non-parasitic in adult life have a parasitic habit, as for instance the larvae of many of the Water-mites and of the Harvest-mites (Trombidium), while other forms live upon organic matter of various kinds, as does the Cheese-mite, Tyroglyphus. k. distinguishing characteristic of the Aearina is the ab- sence of any segmentation and the fusion of head-thorax and abdomen to a single mass (Fig. 208, A). The form of the appendages varies greatly in different genera according to the use to which they are put. The chelicerse (Fig. 209, Md) are. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original McMurrich, J. Playfair (James Playfair), 1859-1939. New York, H. Holt and Company
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