OF ARTS AND SCIENCES: NOVEMBER 14, 1865. 65 



ical process, and, beyond a certain expansion of the parts, by separat- 

 ing the spinners from each other, the only control exercised by the 

 insect is by means of its hinder legs, the tips of which serve to guide 

 the thread, and by grasping it to control the evolution. I have never 

 been able to reel out over three hundred yards at once from a single 

 spider ; but on opening the abdomen, the glands are found still to con- 

 tain more or less gum. Upon three successive days I obtained equal 

 quantities of silk ; so that if, as now seems probable, the emission of 

 the silk is purely mechanical, then a certain degree of preparation is 

 necessary, after it is secreted, before it is ready for use. 



The diameter of the silk as spun by the insect, or as reeled from it, 

 varies from one six-thousandth to one thousandth of an inch ; * it is 

 exceedingly strong, more so in proportion to its bulk than that of the 

 silk-worm ; as is natural, since the spider's thread is made up of hun- 

 dreds and even thousands of minute fibrils, while the common silk 

 is single. The largest threads are those composing the outer layer 

 of the cocoons, but these are evidently compound, and each of the two, 

 three, or four strands is apparently such as proceeds from the single 

 spinners ; the minute fibrils of which have united at once on leaving the 

 spinnerules, so as to form the ordinary silken fibre which generally 

 appears simple under the microscope. 



The habits of this spider ai-e very interesting. It seems to obey 

 three principal instincts : first, to ascend ; second, to seek the light, 

 whether natural or artificial ; and, third, to maintain a position with the 

 head downward. It has eight eye-spots, but, so far as 1 have observed, 

 it can only distinguish light from darkness, and is not able to see 

 objects. There is not here space to give in detail an account of all that 

 I observed in case of several which made their webs in my room in 

 South Carolina; but all seems to indicate that these spiders do not 

 see, as the term is generally understood ; the touch is, however, very 

 acute, and is exercised by the palpi and by the tips of the legs, spe- 

 cially the anterior pair. Unlike some other geometrical spiders, it seizes 

 its prey at once in its jaws, and never envelopes it in a silken net till 

 it has expired. The sense of hearing is evidently very acute. 



It is very quiet in its disposition, and never leaves its web unless 

 molested. The female builds the web, and even carries the male on 

 her back or belly when moving about ; she never attempts to bite 



* The micrometer measurements were made by Mr. R. C. Greenleaf. 



