Other Invertebrate-Animal Study 475 



SPIDERS 

 Teacher's Story 

 jHE spiders are the civil engineers among the small 

 inhabitants of our fields and woods. They build 

 strong suspension bridges, from which they hang 

 nets made with exquisite precision; and they 

 build aeroplanes and balloons, which are more 

 ef&cient than any that we have yet constructed; 

 for although they are not exactly dirigible, yet 

 they carry the little balloonists where they wish 

 to go, and there are few fatal accidents. More- 

 over, the spiders are of much economic impor- 

 tance, since they destroy countless millions of 

 insects every year, most of which are noxious — ■ 

 like flies, mosquitoes, bugs and grasshoppers. 



There is an impression abroad that all spiders are dangerous to handle. 

 This is a mistake ; the bite of any of our common spiders is not nearly 

 so dangerous as the bite of a malaria-laden mosquito. Although there is 

 a little venom injected into the wound by the bite of any spider, yet there 

 is no species found in the Northern States whose bite is sufficiently 

 venomous to be feared. 



There is no need for studying the anatomy of the spider closely in 

 nature-study. Our interest lies much more in the wonderful structures 

 made by the spiders, than in a detailed study of the little creatures them- 

 selves. 



Cobwebs 



"Here shy Arachne winds her endless thread. 

 And weaves her silken tapestry unseen, 

 Veiling the rough-hewn timbers overhead. 

 And looping gossamer festoons httween." 



— Elizabeth Akers. 



Our house spiders are indefatigable curtain-weavers. We never sus- 

 pect their presence, until suddenly their curtains appear before our eyes, 

 in the angles of the ceilings — invisible until laden with dust. The cob- 

 webs are made of crisscrossed lines, which are so placed as to entangle any 

 fly that comes near. The lines are stayed to the sides of the wall and to 

 each other quite firmly, and thus they are able to hold a fly that touches 

 them. The spider is likely to be in its little den at the side of the web; 

 this den may l3e in a crevice in the corner or in a tunnel made of the silk. 

 As soon as a fly becomes entangled in the web the spider runs to it, seizes 

 it in its jaws, sucks its blood, and then throws away the shell, the wings 

 and legs. If a spider is frightened, it at first tries to hide and then may 

 drop by a thread to the floor. If we catch the little acrobat it will usually 

 "play possum" and we may examine it more closely through a lens. We 

 shall find it is quite different in form from an insect. First to be noted, it 

 has eight legs ; but most important of all , it has only two parts to the body. 

 The head and thorax are consolidated into one piece, which is called the 

 cephalothorax. The abdomen has no segments like that of the insects, 

 and is joined to the cephalothorax by a short, narrow stalk. At the front 



