XEST MAKING : ITS ORIGIN AND USE. 331 



governing all creatures and all their actions, has developed in certain ar- 

 thropods the habit of spinning tubes or cylinders as a protection to the 

 body. 



Among the spider fauna this habit is particularly prominent. It does 

 not exist, as with insects, in a larval state, but in the perfect animal, the 

 only one, with possibly one exception, 1 of which we have knowl- 

 edge. The belief has been expressed that both sexes of the Pso- 

 cidse possess the power of spinning a web which McLachliii affirms is not 

 distinguishable from that made by spiders. 2 This habit, which character- 

 izes the larvse of insects, is carried forward to the perfect animal among 

 the Aranese, and, as we have seen, the habit of protecting themselves by 

 tubular spinning work, in one form or another, exists among some spe- 

 cies of every tribe of spiders. 



One who is conversant with insect architecture cannot but be struck 

 with the resemblance between the nests of spiders and those made by the 

 larva? of certain insects. Brief allusion has already been made to this, but 

 it may be worth while to call attention more distinctly thereto. 



Very often I have met, along the seashore in New Jersey, a species of 

 leaf roller Tortricid moth, whose species I do not know, that has reminded 

 me of the nests of Epeira trifolium spun among the ferns, and 

 Epeira which is one of the most beautiful examples of the nesting habit 

 ... to be found among spiders. The two objects may sometimes be 



seen almost side by side, and even the most casual observer 

 would scarcely fail to note that they must have been constructed upon the 

 same fundamental principles of architectural instinct. There are, of course, 

 differences which one may note without very acute perception ; but the 

 resemblances are certainly worthy of consideration, and it is to these that I 

 have here wished to call attention. (See Figs. 316 and 317.) 



The nest of Theridium riparium is constructed on very much the same 

 principle as that of the larva of the caddis fly, or case worm, a Neurop- 

 terous insect which is very well known, and whose remarkable 

 Theridi- architectural habit has excited the interest of naturalists. Sev- 

 the Cad- era ^ i^ ustrat i ns f * ne nests of this insect are given. 3 The first 

 dis Ply. represents a case made of bits of moss, and is the work of Lim- 

 nophilus rhombicus. (Fig. 323.) The second represents the case 

 worm, found in great abundance by Professor Packard in Labrador, and 

 which he supposes to be the work of Limnophilus subpunctulatus, the 

 most abundant species found in Labrador. The case is straight, cylindri- 

 cal, and built of coarse gravel, and the larva is a thick, cylindrical, whitish 

 worm. The next figure (Fig. 320) represents the nest of Limnophilus 



1 Psocus sexpunctatus. See a note of the author in Proceed. Acad. Nat. Sci. Phila., 1883, 

 page 278. 



2 Monograph British Psocidre, Entomological Monthly Magazine, Vol. Ill, 1866-7, page 268. 



3 These are copied from Packard's "Guide to the Study of Insects," page 617. 



