. The animals and man; an elementary textbook of zoology and human physiology. Zoology; Physiology. ARTHROPODS AND MOLLUSCS i6S cheese-mites, the dreaded itch-mite and the chigger are familiar examples of these degraded arachnids, and the wood-ticks, dog- and chicken-ticks are common examples of the larger blood-sucking forms. The body in both mites and ticks is very compact, the two body-regions, cephalo- thorax and abdomen, being closely fused. Various species of ticks have been proved to be the carriers of the germs of certain diseases of human beings and domesticated animals (see Chapter X
. The animals and man; an elementary textbook of zoology and human physiology. Zoology; Physiology. ARTHROPODS AND MOLLUSCS i6S cheese-mites, the dreaded itch-mite and the chigger are familiar examples of these degraded arachnids, and the wood-ticks, dog- and chicken-ticks are common examples of the larger blood-sucking forms. The body in both mites and ticks is very compact, the two body-regions, cephalo- thorax and abdomen, being closely fused. Various species of ticks have been proved to be the carriers of the germs of certain diseases of human beings and domesticated animals (see Chapter XII). The spiders have the abdomen distinctly set off from the cepha- lothorax. The eyes (fig. 76) vary in number and arrange- ment, the mandibles are large, each bei^g composed of two parts, a basal hair-covered part, the falx, and a terminal smooth, shining, slender, sharp-pointed part, the fang, which is mova- bly articulated with the falx (fig. 76). In the falx is a poison- sac from which poison flows through the hollow fang and out at its tip. The legs vary in rela- tive length in different spiders, and each is made up of seven joints. The spinnerets (fig. 77), which are situated at the tip of the abdomen, are six in number (a few spiders have only four), and are like httle short fingers. They have at their tips many fine little spirming-tubes from each of which a fine silken thread issues when the spider is spinning. These many fine threads fuse as they issue to form a single strong cable or sometimes a flat rather broad band. The spinnerets are movable, and by their manipulation the desired kind of line is produced. The silk comes from. Fig. 74. The cheese-mite, Tyroglyphus siro. (Greatly enlarged; after Berlese.). 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 Kellogg, Vernon L. (Vernon Lyman), 1867-
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Keywords: ., bookcentury1900, bookd, booksubjectphysiology, booksubjectzoology
