LAEVAL HABITS OF THE TIGEE BEETLES. 179 



Species which lay in moist sand, after a rain may do so on the top of a 

 dune, and the larvae arising from such eggs be subjected to dry conditions 

 later unless they make some adjustment. 



VI. General Discussion. 



We have noted that the imagoes of many species undergo a series of 

 changes, particularly in colour, after they have appeared in their regular 

 habitats ; that in some species this change continues to the time of death ; and 

 furthermore that the two generations of limhalis, generosa, and particularly 

 hirticollis, overlap so as to mix those that have just emerged with the old 

 individuals that have hibernated. The importance of considering these facts 

 in the study of variation need hardly be mentioned. Not to know the life- 

 histories would lead to endless confusion in the study of geographical variation 

 and of variation from generation to generation. 



The possibility of differences in environmental conditions in the same 

 brood of Leptinotarsa, due to periods of extreme weather, has been noted by 

 Tower. In Cicindela we have two additional possibilities : (a) that of the 

 pupal cells being constructed at very different distances from the surface by 

 different individuals ; and (h) of the entire larval life of some individuals 

 being passed under unusual conditions because of the responses to the 

 environmental peculiarities and necessary limitations in connection with 

 egg-laying in the particular soil which a given species selects. Since the 

 young stages of some species are sensitive, at least during the pre-pupal 

 and pupal periods, to external stimuli, and since the results of such stimuli 

 are manifest in modifications of colour and colour pattern, there is opportunity 

 for soil temperature and moisture to influence variability. 



Nor is this the only importance to be attached to these habits and 

 responses. The animals select a definite place in which to lay their eggs 

 and the larvse of most species never leave their burrows. The migrating 

 larvse select a place themselves, and if it is not found soon, they die. All 

 this leads to a definite distribution dependent upon the domestic habits and 

 instincts of the species. This distribution I propose to call ecological dis- 

 tribution, from Haeckel's * definition of that term. Ecological distribution 

 will be discussed in a succeeding paper. 



YII. SUMMAEY. 



1. The eggs are laid in open burrows made by the ovipositor as in the 

 European species ; the period of incubation is usually about two weeks, 

 (pp. 160-161.) 



* Ecology is the science of the domestic side of organic life, of the life needs of organisms 

 and their relation to other organisms with which they live. — ' Wonders of Life,' 1905. 



