SOCIAL CATERPILLARS. 671 



The cggH lire tapering, barrel-shaped, witli numerous ribs and of a yellow 

 color when just laid. The larvae have a cylindrical and nearly equal 

 body, supplied with a dorsal row and on each side, four other rows of 

 conical tubercular spines, two pairs above and two below the spiracles. 

 They are dark orange with a dusky, longitudinal, stigniatal line, and are 

 lu'avily marked with l)lack in transverse patterns. The chrysalids are 

 somewhat rounded, elongated, Avitli full abdomen and apically tumid wing- 

 thecae. They are j)ale yellowish in color, the wings dashed with black, 

 and the dorsal surface is studded with small, conical tubercles which are 

 set off by basal dark-colored rings. 



EXCURSUS XXL— CONPANIONSHIP AND COMMENSALISM 

 AMONG CATERPILLARS. 



Nou v'accorgete voi die noi siam vermi 

 Nati aforinar I'angelica farfalla, 

 Che vola alia giustizia senza schermi? 



Dantk. — Purgatorio. 

 Do ye not conipreheml that we are worms. 

 Born to bring forth the angelic butterfly 

 That flieth unto judgment without screen? 



Longfelloio^s translation. 



As a general rule, caterpillars of butterflies live solitary lives through- 

 out their entire existence. The mother drops an egg here and there upon 

 a spot suitable for the food of its young, and here the caterpillar takes up 

 its abode with more or less wanderings. In two of the four families of 

 butterflies there is scarcely a single exception known to this rule, but in 

 the highest family and in a few instances in the Papilionidae, caterpillars 

 during at least a portion of their lives are more or less gregarious. 

 Whenever the caterpillars are strictly gregarious, the eggs are invariably 

 laid in clusters ; there are, however, some butterflies Avhich lay their eggs 

 in small clusters, whose caterpillars are not properly gregarious ; yet all 

 such are closely related to others whose caterpillars are gregarious, so 

 that we find every gradation from solitary to social. There are also 

 some caterpillars which are gregarious in their early life, but afterward 

 part company. In such cases the caterpillar usually hibernates, and its 

 social life lasts to some degree throughout the autumn and winter, the 

 company dispersing at the renewal of activity in the spring. Indeed, in 

 almost all cases, the association is most conspicuous in early life, when 

 the caterpillars feed in rows upon the same leaf in such close proximity 

 that it would seem to interfere Avith convenience. Sometimes this is the 

 only mark of their social nature ; but as all caterpillars spin more or less 

 silk in moving about, a web of greater or lees extent generally accompanies 

 a colony, and in some cases the community constructs a close structure 

 within which they retire to rest or to moult. A Mexican buttei-fly, 



