270 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Fig. 244. Camera lu- 

 cida outline, greatly 

 magnified, of a sec- 

 tion of the muscular 

 coating of poison sac 

 of Epeira domicilio- 

 rum. 



Fig. 246 shows the poison sac, gland, and one of the fangs of the 

 Mason spider (Nemesia cementaria) as dissected hy Blanchard.i The ver- 

 tical articulation of the fangs, or movement up and down, which char- 

 acterizes this tribe of spiders, 

 nia}^ be noted in the cut. Fig. 

 247 represents the formidable 

 mandibles of the large My- 

 gale, popularly known as the 

 " tarantula," drawn twice the 

 size of nature. The outlets 

 for the poison from the fangs 

 are here very manifest. They 

 are situated near the point of 

 the inner surface, and are of 

 the shape represented in the 

 figure. On one side of the 

 falx is a formidable row of ten teeth. The other side is protected by a 

 picket of closely placed stiff red bristles. It might be expected that such 

 a formidable armature would certainly inflict a grievous hurt, whatever 

 may be the case concerning the feebler armature of our ordinary familiar 

 spider fauna. 



Another illustration of these organs is given at Fig. 248, which repre- 

 sents the fang and falx of an immature Drassus, multiplied about twelve 

 times, taken from a camera lucida drawing made by the late Mr. Richard 

 Beck. 2 The manner in which the falces and fangs are related to the mouth 

 organs is shown at Fig. 249, which is a view from 

 beneath of the cephalothorax of Ejieira quadrata. 

 The lip is seen at the tip of the sternum, which 

 lies just under the maxillne, which organs in turn 

 are situated just beneath the falx. 



The moults of spiders form admirable specimens 

 in which to examine microscopically the external 

 character of the fang. They not only show the 

 opening far more distinctly than the entire organ 

 taken from the animal, but they present the fangs 

 in a most favorable position for examination. 



In view of the above results, we are free to say fig.245. poison giand (g), duct (d), 



... and fang (f) of Epeira diadema- 



that as far as the testmiony of anatomy goes, it is ^^ ^ j^e point of fang yet 

 plain that spiders of all tribes are abundantly more enlarged, to show the ex- 



t i ,. 1 1 • ... ternal opening, o. (After Davis.) 



provided with an armature for dealing an injurious 



wound to those whom they strike. One can hardly suppose that such a 

 gland as I have described, with such an attachment, is intended to secrete 

 any other substance than one which provides for the defense or nourish- 

 ment of its possessor. 



• Cuvier, Eegn. Anim. Arachnides. 



2 "Science Gossip," 1866, page 202. 



