ADAPTATION OF PUPA TO ITS SURROUNDINGS 631 



usually brief, period of life, and transmitted by the action of syn- 

 chronous heredity. 



The pupae of certain insects are quite active, thus that of Ra- 

 phidia, unlike that of Sialis, before its final ecdysis regains its 

 activity and is able to run about. (Sharp, p. 448.) 



a. The pupa considered in reference to its adaptation to its 

 surroundings and its relation to phylogeny 



The form of the pupa is a very variable one, as even in Lepidoptera 

 it is not entirely easy to draw the line between a pupa libera and a 

 pupa obtecta (Fig. 578) ; and though the period is one of inactivity, yet 

 when they are not in cocoons or in the earth in subterranean cells, 

 their form is more or less variable and adapted to changes in their 

 surroundings. Even in the obtected pupa of butterflies, there is, 

 as every one knows, considerable variability of shape and of arma- 

 ture, which seems to be in direct adaptability to the nature of their 

 environment. Scudder has well shown that in certain chrysalids, 

 such as those of the Nymphalidse, which are variously tuberculated, 

 and hang suspended by the tail, and often hibernate, these projec- 

 tions serve to protect the body. All chrysalids with projections or 

 ridges on different parts of the body, being otherwise unprotected, 

 move freely when struck by gusts of wind, hence " the greater the 

 danger to the chrysalis from surrounding objects, the greater its 

 protection by horny tubercles and roughened callous ridges." The 

 greater the protection possessed in other ways, as by firm swathing 

 or a safe retreat, the smoother the surface of the body and the more 

 regular and rounded its contours. The tendency to protection by 

 tubercles is especially noticeable in certain South American chrysa- 

 lids of nymphalid butterflies. This response to the stimuli of blows 

 or shocks is also accompanied by a sensitiveness to the stimulus of 

 too strong light. 



Previously Scudder l had made the important suggestion that the 

 smooth crescent-shaped belt of the "glazed eye" or "eyepiece" of 

 chrysalids is, as an external covering of the eye, midway between 

 that of the caterpillar and the perfect insect, and he asks : " May it 

 not be a relic of the past, the external organ of what once was ? 



1 Butterflies, their structure, changes, and life-histories. New York, 1881, pp. 37-42. 

 Butterflies of the Eastern United States and Canada, 1888, 1889. Also, Frail children 

 of the air, 1895, pp. 232, 233 a. Dr. Chapman, however, finds that this piece in 

 micropupae has no connection whatever with the head or eye, but belongs rather 

 with the prothoraeic segment. (Trans. Ent. Soc. London, 1893, p. 102.) We have been 

 able to confirm his statements, but still this piece is peculiar to the pupal state. 



