502 ARACHNIDA. 



The males are distinguished from the females by the smaller size 

 of the abdomen. The females are always oviparous, and frequently 

 carry their eggs about in special webs (Th&ridivm, Dolomedes). In 

 the male the pedipalpus is modified to form a copulatory organ ; the 

 thickened and excavated terminal joint is spoon-shaped, and possesses a 

 vesicular copulatory appendage with a spirally-twisted fibre (fig. 403). 

 Before copulation the male fills this appendage with sperm, and at 

 the moment of coitus introduces the terminal fibre into the female 

 genital opening (fig. 404). Sometimes the two sexes live peacefully 

 near each other on neighbouring webs, or even for a time on the 

 same web ; in other cases the female, which is the stronger animal, 

 lies in wait for the male in the same way as she does for all animals 

 weaker than herself, and does not spare him even during or after 

 copulation ; the male, therefore, only approaches her with the greatest 



caution. 



Development. 



-The segmenta- 

 tion of the ovum is 

 centrolecithal (fig. 

 107). The em- 

 bryos possess, in 

 addition to the 

 thoracic appen- 

 dages, the rudi- 



FIG. 404. Male and female of merits of abdomi- FIG. 405. Spider embryo (after 



Liin/iMa, during copulation m ] f ee which Balfour). AF, Rudiments of 



(after O. Herman). abdominal feet. 



subsequentlyabort 



(fig. 405). The young, when hatched, already possess the form and 

 appendages of the adult. They are not, however, sufficiently de- 

 veloped before the first moult to spin or to capture prey. It is only 

 after the moult that they become capable of performing these 

 functions, leave the web of the egg membranes, and begin to spin 

 threads and to capture small insects. The threads which we find 

 floating in the air in great numbers in autumn and are known as 

 gossamer threads are the work of young Spiders, which raise them- 

 selves in the air by their means, and pass the winter in sheltered 

 places. 



The habits of spiders are so remarkable that they have for a long 

 time excited the interest of observers. All spiders are predacious, 

 and suck the juices of other insects ; nevertheless, the manner in 

 which they get possession of their prey varies much, and often 



