214 PROCEEDINGS OF THE ACADEMY OF [1888. 



the last named dates the younglings make their exode, and after be- 

 ing dispersed in the manner usual to spiderlings, proceed to make 

 tiny tubes which are miniatures of the parent nest. As the develop- 

 ment of spider life in Great Britain is later than in the United 

 States the tubelets of the young of Abbot's Atypus may be looked 

 for in the early autumn. Some of the Florida specimens which I 

 collected in April within their tubes, I judge to be members of the 

 preceding autumn broods. 



VI. ORIGIN AND RELATIONS OF THE TUBEWEAVING HABIT. 



The tube-making faculty appears to be, as far as secondary causes 

 are concerned, the natural result of the instinct of self-protection. 

 It is perhaps most natural that the lower animals should seek to 

 protect themselves within barriers formed by their body secretions, 

 as is the case among the larvre of many insects. The restless move- 

 ments of the body characteristic of these creatures, conjoined with 

 the instinct to cover themselves up, to protect themselves from un- 

 favorable weather changes and from the ap])roach of' enemies, may 

 be a sufficient natural explanation of the origin of the tube-making 

 habit. Thus the silk moth larva while secreting silk from the 

 glands which open on the under lip, moves backward and forward 

 continually distributing its secretions, and at the same time by the 

 motion of its body limits them to the borders of the space around 

 which it moves. In the same way the social caterpillars have 

 learned to shut themselves within their Avell known tent, which 

 presents so largely the appearance of a designed structure, but which, 

 in its origin, at least, may have been quite as much the result of 

 accident, the silken secretion simply hardening around the limits of 

 the space through which the restless creatures move, and which by 

 their motions they keep free from threads. In like manner the 

 larva of the ant, at the moment when Nature brings upon it the 

 sense of the great change from its larval to its pupal estate, moves 

 backward and forward within a narrow space secreting its delicate 

 silk, which by its movements is pushed from direct contact with its 

 body, and hardens into the little case or pouch in which itself at 

 last is encompassed. Thus, in an entirely natural way, we may 

 suppose that the Great Over-Force while planning and directing, 

 preserving and governing all creatures and all their actions, has 

 developed the interesting habit of sjiinning tubes or cylinders as a 

 protection to the body. 



