. Elementary zoology. Zoology. so fused that, except in the scorpions, they are usually indistinguishable. There are no antennae, the eyes are simple, the mouth-parts fitted for biting, and there are four pairs of legs. In their internal anatomy the arach- nids show in some forms a pecu- liar modification of the respiratory organs, the tracheae being flat and leaf-like and massed together in a few groups rather than being tubular and ramifying through the body. The dorsal vessel or heart usu- ally has a few blood-vessels or arteries running from it. This class is divided into three orders, the


. Elementary zoology. Zoology. so fused that, except in the scorpions, they are usually indistinguishable. There are no antennae, the eyes are simple, the mouth-parts fitted for biting, and there are four pairs of legs. In their internal anatomy the arach- nids show in some forms a pecu- liar modification of the respiratory organs, the tracheae being flat and leaf-like and massed together in a few groups rather than being tubular and ramifying through the body. The dorsal vessel or heart usu- ally has a few blood-vessels or arteries running from it. This class is divided into three orders, the Arthrogastra, or scorpions, the Acarina, * o r mites and ticks, and the Araneina, or spiders. The scorpions (fig. 89) have the posterior six segments of the abdomen much narrower than the seven anterior seg- ments and forming a tail which bears at its tip a poison-fang or sting. This sting is used to kill prey, insects and other small animals. The tail can be darted forwards over the body to strike prey which has been previously FlG< seized by the large pincer-like maxillary palpi. Scorpions are common in warm regions, about twenty species being Fig. 89.—A scorpion Cen- trums sp., from Cali- fornia. (From specimen.). -The cheese-mite, Ty- roglyphus szro, greatly en- larged. (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), 1867-1937. New York : H. Holt and company


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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1902