Annual Address of V. T. Chambers^ Esq. 73 



the medium in wliicli the organism lives; and the}' are accompanied by 

 well marked changes in the internal structure of the animal. But be- 

 sides the influence of food and temperature there appears also to be an 

 unknown factor which directs the course of development, and holds in 

 subordination the influences both of food and temperature. 



The number of moults which insects undergo varies in diff"erent 

 species, and sometimes (under the influence of the unknown factor to 

 which I have alluded) even in the same species. Thus, according to Sir 

 J.Lubbock, Chloeon dimidiattcm, a, neuropterous insect, moults seven- 

 teen times ; whilst some of the smaller Lepidoptera moult only once in 

 the larval state, once passing into the pupa, and again into the moth 

 or imago as is the case in the genus PhyLlocnistis; and some as in the 

 genus Nepticula, moult onl}- twice; once when the larvae becomes a pupa, 

 and again when the pupa becomes a moth. The usual number of skin 

 sheddings among Lepidoptera however is six, including those by which 

 the pupa and the imago are disclosed. But there are many exceptions 

 to this rule. Thus the larvee of Sphinx h'gicstris, according to Newport, 

 moults six times (but it ma}- be possible that Newport includes in this 

 number the moult of the larva into the pupa state) ; and Cuvier states 

 that the \avva. of Arctia caja moults five to ten times. It is possible, 

 as Dr. Packard has already suggested, in a note in " Nature^''' that there 

 is some error in this statement. Rennie and Westwood, in their "• Insect 

 Transformations," state that caterpillars generally moult five times, but 

 sometimes seven or even ten times. Some confusion as to the number 

 no doubt has grown out of the fact that some authors include the 

 moult by which the caterpillar passes into the pupa state, whilst others 

 exclude it. Including this moult, the ordinary number is five; that is, 

 there are ordinarily five stages of larval life. 



Mr. H. "W. Edwards has recently, in the pages of the Canadian 

 Entomologist and of Psyche, published mau}^ valuable observations on 

 the life histories of our American butterfiies, from which it appears 

 that in Phyciodes tharos, and in P. nycteis, Danais ai-chipjnis^ ■- atyrus 

 nephele, Lyccena pseudargiolus, Neonympha sosybius, and iV. eurythis, 

 there are five stages; and in Limenitis arthemis, and L. dystpjnis, six 

 whilst in Ccenonympha gemma there are onl}' four. According to 

 Lintner the larva of the moth, Ceratomia quadrico7'nis, passes through 

 five stages; and according to Kirb}^ there is the same number in 

 Apatura celtis, and in the female of Orgyia leucostigma, whilst there 

 are only four in the male; and Hemilenca maia is said "to be one of 

 the few larvse which passes through" six stages. In Hyperchiria lo 

 t>here are six stages; in Tliyridopteryx ephemeroi formis only four. 



