342 ZOOLOGY. 



Order 5. Arthrogastra. — In this group belong scor- 

 pions (Fig. 313), fiilse scorpions (Fig. 314), the whip scor- 

 pions, and the harvest-man {Phalangium). In all these 

 forms the abdomen is plainly segmented, the segments not 

 being visible in the mites or spiders. Usually the maxillary 

 palpi are much enlarged, and end in claws. The scorpion 

 is viviparous, the young being brought forth alive. The 

 young scorpions cling to the back of the mother. The sting 

 of the scorpion is lodged in the tail, which is perforated, 

 and contains in the bulbous enlargement an active poison. 

 Though producing sickness, pain, and swelling in the arm, 

 the sting of the scorpion is seldom fatal. 



The little false-scorpions (Chelifer, Fig. 314) often occur in 

 books, under the bark of trees, and under stones. The whip- 

 scorpion is confined to warm countries. TIielypAonus gigan- 

 teus Lucas occurs in ISTew Mexico and Mexico. Its abdomen 

 ends in a long lash-like appendage. Its bite is poisonous. 

 The harvest-men, or daddy-long-legs, are common in dark 

 places about houses. They feed on plant-lice. Our common 

 species is Phalangium dorsatum Say. 



Order 6. Araneina. — The spiders are always recogniza- 

 ble by their spherical abdomen, attached by a slender pedicel 

 to the head-thorax. They breathe, like the scorpions, both 

 by lungs as well as by trachese, and the young resemble the 

 parent in having four pairs of feet. 



The development of the spider has some peculiarities not 

 found in the higher insects. The egg undergoes total seg- 

 mentation. The germ is somewhat worm-like, as in Fig. 

 315, then, as in C, the primitive band forms, with head and 

 tail end much alike. Afterward (Fig. 316) the head ac- 

 celerates in development, and the appendages begin to bud 

 out, six pairs of abdominal limbs appearing and then totally 

 disappearing, except the three pairs of spinnerets, as if the 

 spiders were descended originally from some Myriopod-like 

 form. The mandibles are vertical, and end in hollow points, 

 through which the poison exudes, the two poison -glands 

 being situated in the head. The male spider is usually 

 much smaller than the female ; the latter lay their eggs in 

 silken cocoons. The tarantula {Lycosa) usually lives in 



