LIFE-HISTORIES OF THE TIGER BEETLES, 157 



Life-Histories and Larval Habits o£ the Tiger Beetles {Cicindelidce). 

 By Victor Ernest Shelford, S.B., Ph.D. (Chicago). (Communicated 

 by the Rev. Canon Fowler, M.A., F.L.S.) 



(Plates 23-26.) 



[Read 20th February, 1908.] 



I. Introduction. 



During the past quarter century, the consideration of life-histories and habits 

 as a basis for experimental work and for the study of distribution, variation 

 and other evolutionary topics has been far too much neglected. In the study 

 of variation, investigators have too often collected large numbers of specimens, 

 arranged them in classes, calculated indices, constructed curves, and drawn 

 conclusions regarding the direction of evolution without knowing the life- 

 history of the form and without determining whether the characters studied 

 are easily modified by varying conditions during development, or whether 

 they change during the life of the individual. 



Recent studies of the variation of the potato beetle from generation to 

 generation, by Tower, and of seasonal changes in the number of ray flowers 

 of certain Compositce, by Tower, Shull and others, have called attention to 

 the great liability to error in investigations conducted in this manner. 



An analysis of the environmental conditions of an organism during 

 development cannot be made until the complete life-cycle is known. The 

 responses and habits of the adult Tiger Beetles at the time of laying, as we 

 shall note later, and of the larvae, especially at the time of preparation for 

 pupation, determine in many cases the conditions under which later stages 

 must be passed. In the pupal and prepupal stages at least, these organisms 

 are sensitive to external stimuli. 



It is my purpose to present in this paper the general outlines of those 

 activities and reactions connected with reproduction, which have a special 

 bearing on the more general papers to follow. The succeeding papers will 

 deal with the following topics : — distribution, variation, the effects of varying 

 environmental conditions during development, an analysis of the colour 

 patterns, a discussion of race tendencies of the genus Cicindela, and the 

 bearing of the whole on the problem of evolution. The data on the selection 

 of habitat and on colour-changes herein mentioned, will be presented in detail 

 in another connection. 



II. Previous accounts of Larv^ and Life-Histories. 



The larva and larval habits of a European species, Cicindela campest7'is, 

 Linn., were described by the early writers on natural history and are better 



