In remarkable contrast to the round-bodied mites are the scorpions (Fig. 168), in which the tail is sometimes two inches in length and armed with a sharp, daggerlike sting, provided with a poison apparatus. The scorpions of the largest size are often found in the tropics in the same locality with centipeds, under board piles and in dark places, coming out at night to prey upon small insects, which they seize with their crablike claws and tear apart. If the insect struggles violently, the scorpion raises its tail over its back and pierces it with its dagger, paralyzing it. In striking at other enemies the scorpion whirls about, keeping its tail toward them, repeatedly striking down and using its jointed tail with marvelous ingenuity. A few years ago these scorpions were common on the Florida Reef and were frequently killed in my own house at night. The pain resulting from the sting was about as disagreeable as that occasioned by a wasp. These scorpions were about three inches in length, but in Ceylon very much larger ones have been seen, and known to catch birds. The young scorpions are born alive and cling to the mother. The little book scorpion, the large whip scorpion, and the daddy longlegs, or harvestman, a harmless and sociable insect, are related to the true scorpions. XX. THE SPIDERS A little insect half as large as a grain of corn, finds itself on a limb high above ground and is desirous of reaching another, five feet away. It is not a jumper, at least it could not hope to cover this distance; neither has it wings. But it has a marvelous silk-manufacturing apparatus, known as spinnerets (Fig. 169), and elevating its abdomen it reels off a thread which the wind carries across the chasm where it lodges. Across the single cord the spider runs, the act being suggestive of the intelligence of these insects. [Illustration: FIG. 169.--Spinnerets of a spider.] The common garden spider (Fig. 170), which may illustrate the group, is seen to differ very materially from the scorpion. The abdomen is not ringed or made up of segments, but is large and plump, and connected with the thorax by a delicate cord or pedicel. [Illustration: FIG. 170.--Garden spider, upper and lower surface.] The spiders, as we have seen, have a spinning arrangement by which they form beautiful webs or nets to capture prey. By this silken cord they can lower themselves from great heights. The single thread which supports them is made up of a number of minute threads (Fig. 171). The webs are formed in endless variety and with all the skill of a bridge maker, being guyed, supported, and braced in a manner which, if the work of man, would be said to be the result of endless study. They are perfect in their arrangement, and each web is a study in geometry, yet the spider builds it with the greatest rapidity, never hesitating in the making or repairing. [Illustration: FIG. 171.--Structure of a spider's web.] [Illustration: FIG. 172.--Spider and its web or trap.]