Wilder.] 206 



by carrying the thread from the anterior pair of mammulaB upon one 

 part of a spindle and that from the posterior pair upon another, guiding 

 them with pins while the spindle was in motion ; the result being the 

 formation of two circles of silk, one of a golden, the other of a sil- 

 ver color, as In one of the specimens exhibited ; morever. If while both 

 threads are being drawn out, they are slackened, the lower silver 

 thread will wrinkle and fly up, being inelastic, while the other will 

 contract and, within certain limits, preserve Its direction. At that 

 time the existence of a smaller pair of mammulas intermediate be- 

 tween the other two, was unknown to me, and It Is possible that the 

 yellow line proceeded from them, and that both the larger pair yield 

 the white silk. Most of these experiments were made In the field under 

 unfavorable circumstances and will be more accurately repeated. 



The careful dissection of an alcoholic specimen will readily discover 

 the organs from which this silk proceeds, and which have been described 

 in other species by several authors ; the preparation exhibited to the 

 Society shows one set of silk-glands consisting of six elongated yellow 

 bodies, more or less convoluted and measuring about one-third of an 

 Inch In length, lying under the integument of the lower surface of 

 the abdomen, three upon each side of the middle line ; the excreting 

 ducts, one for each gland, are also plainly visible. But beside these, 

 there are to be found at least four more glands, of which one pair 

 shorter but thicker and larger, and also of a yellow color, are located In 

 the upper and anterior angles of the abdomen; while the other two 

 glands are white, or transparent, and lie nearly in the center of the 

 abdomen ; the ducts of all these glands are easily traced to the region 

 of the spinnerets, but I have not yet observed the precise mode of their 

 termination. It will be noticed that the yellow silk is secreted In 

 greater abundance, as also that It Is more extensively employed in the 

 construction of the web. 



All these glands contain a semi-fluid and very viscid gum which may 

 be drawn out into threads of variable diameter; these however, being 

 single and not, like those spun by the spider, minutely compound, 

 break up on being sharply bent. 



A familiar, but thus far unexplained, fact is, that while the yellow 

 thread as spun by the spider in its web is so exceedingly viscid on ac- 

 count of the numerous globules of gum with which it is studded, as to 

 follow the point of a pin, tins same yellow silk when reeled from 

 the Insect, whether slowly or rapidly, and also when employed by the 

 spider to form the cocoon about her eggs. Is perfectly dry and much 

 less elastic and yielding, though still more so than the white variety. 

 I have put several specimens under the influence of chloroform which 

 apparently has no effect upon the evolution of silk. 



I have never been able to reel above three hundred yards of silk from 



