Annual Address of V. T. Chambers, Esq. Ih 



of Insects," seems to think that there is nothing more remarkable 

 about the metamorphoses of insects than about those of man, each 

 being a mere process of growth and development. But in man there 

 is no cast of the entire integument which occurs periodically in in- 

 sects. 



No satisfactory explanation of the metamorphoses of either verte- 

 brates or articulates has ever been given, or perhaps ever will be given. 

 The inquirj' simply resolves itself into the question, wh}' growth and 

 development are what we see them to be, instead of being something 

 else, we know not what — perhaps a mere formless mass of cells. 



Prof. A. M. Duncan [Nature, v. 7, p, 30) states that "the skin- 

 sheddings (of insects) have a definite relation to the increasing size of 

 the insect, but they are not simple changes of skin, because the old one 

 has become too light for its rapidly growing possessor. They ac- 

 company certain important changes within the insect.'' And the facts 

 which he gives as to the structure of the intestinal canal, support his 

 statement, as also do those subsequently to be given in this address as 

 to certain other organs, in which also the exact relation of the "skin- 

 sheddings" to the increasing size of the larvge of Lithocolletis will be 

 made evident. These facts, or rather facts of the same character as 

 these presently to be given as to Lithocolletis, have at various times 

 been stated with reference to other insects. 



Thus H. S. Edwards states that the larva of Phycoides tharos, in its 

 first stage, measures in parts of an inch .06 in length, in its 2d stage 

 .22, in the 3d .45, and in the fourth form .85 to .90; that is the larva 

 in each stage is about twice as long as it was in the preceding stage. 

 He also states that the larva of Satijrus nephele in its several stages 

 measures respectively .1, .16, .30, .44 and .95 to 3.2 in length. An 

 approach to a regular ratio of size in the several stages is here apparent, 

 but it is not so distinct as in P. tharos. Just here I will add that the 

 larvae of Lithocolletis, especially those of the group of flat larvjB, are 

 more rigid, and less contractile than those of higher groups, and, there- 

 fore, afford greater facility for measurement; and besides it does not 

 appear from the observations of Mr. Edwards, or of the other authors 

 whom I shall quote, exactly at what period of the respective larval 

 stages the measurements were made. The measurements ought to be 

 made at exactly corresponding periods of the several stages, and the 

 best period is wdien the larvae has ceased to feed at the end of each 

 stage, when the full growth for that stage has been attained. It is at 

 that period that I have made the measurements of Lithocolletis here- 

 after detailed. 



