178 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



^.:^^>SS3STSK-^^. 



Fig. 165. Spinning organs of Clubiona, 

 showing tlie cribelluni, cb. P, pos- 

 terior; m, middle; a, anterior spin- 

 nerets; ca, calamistriini. (After 

 Blackwall.) 



an old fasliioned spinning wheel, and is apparently used to sejjarate into 

 a flossy mass the threads of silk as they issue from the spinning glands. 

 Bertkau, in an article on the cribcllum and calamistrum, has shown cer- 

 tain secreting glands at the ends of the fine tuljcs which have their 

 outlets in the former organ. It is not improbable, in view^ of this dis- 

 covery, that the viscidity of the flocculent spirals 

 of Uloborus and other spiders possessing this 

 organ is caused in some measure by a slight 

 secretion from these glands. 



It is the possession of criljcUum and cala- 

 mistrum by Uloborus and Ilyptiotes which has 

 led various araeiniologists to sep)arate 

 Calamis- tj^ggg i^^,q genera from the Orbweavers. 

 C -ibellum E'^^'^^'ton, for example, following Black- 

 wall, Keyserling, and Bertkau, assigns 

 them to the Clubionidse. Without entering at 

 length into the reasons, based upon structure, for 

 dissenting from this opinion, I have felt con- 

 strained, on the grounds of their spinningwork 

 alone, to place botli these genera among the Orbitelarise, where indeed such 

 a distinguished systematic arachnologist as Professor Thorell has already 

 j)laced them, and continues to keej) them, notwitli.standing all the objec- 

 tions that have been advanced by the able naturalists who have espoused 

 the other view. 



Mr. Emerton has made some studies of the web of Uloborus Walck- 



enaerius, the common species of Northern Europe. I rej^roduce his figure 



(Fig. 167), whicli represents an unfinished web of this species 



uropean ^^^^^ j^^ France. It shows the central part still occupied by the 



Species. ... ., «-iT 1-11 • 



preliminary spirals or scafiolding, wliile tlie outer part is covered 



with curled threads, and the smooth spirals cut away (or not yet inserted), 

 leaving thickened si)ots or ribbons on the rays. In the finished web most 

 of tlie spirals jiass regularlj^ around, but the outer ones are often more or 

 less irregular, as in Epeira webs, according to the shape of the .spare in 

 which the web is made. 



According to this author, Uloborus, after inclosing her eggs in the eo- 

 coon, becomes careless about her web, 

 and repairs it only enough to keep the 

 cocoons in place, so that many imper- 

 fect and irregular w'ebs are found at 

 the cocooning season. The only web 

 of Uloborus plumipes seen by Emerton 

 was imperfect from the above cause, but was evidently tlie remains of a 

 nearly round web, the rays meeting somewliat nearer the up]iei- 1li:in tlie 

 lower (>dge. 



Fig. 166. 



Curled thread of Clld)iona. 

 (After Staveley.) 



