8 Journal New York Entomological Society. ^^'°^- ^^■ 



of the species to changing environment; tranqucharica and loiigilabris 

 appear to have had a similar history, both driven far south during the 

 glacial period, both returning northward with its retreat, both strong 

 species represented by numerous varieties and abundant wherever 

 they occur. But the one has survived the changing climate south- 

 ward and continues to thrive in the austral zone as well as in the 

 transition and boreal ; while the other, longilabris, though it must 

 have been driven far south of this latitude during the ice age, except 

 on the probable assumption that it survived the ice age exclusively 

 in isolated, northern, sheltered localities, has failed to survive even 

 in the mountains and is now strictly confined to the boreal zone, hav- 

 ing perished elsewhere as the temperature increased. The only cause 

 I can imagine is that tranqucbarica could and did adapt itself to the 

 growing warmth of the Carolinas. Georgia and Louisiana and sur- 

 vives, while longilabris could not and so perished. It had the same 

 chance but could not take advantage of it. 



Accidents. — So powerfully deterrent to extended distribution is 

 the influence of environment combined with the wilful behavior of 

 the insects themselves that the marvel would be that many have 

 spread so far were it not for the results of another set of factors that 

 my friend Chas. R. Plunkett. who was with us at the last meeting, 

 summarized under the name accidents, meaning thereby winds, cur- 

 rents, human interference, geological changes, anything acting inde- 

 pendent of or contrary to the will of the insects. The widespread 

 distribution of pnnctitlata. flying as it does to lights at night and 

 thereby exposing itself to the action of wind, and capable moreover of 

 making itself at home in any garden path, is a case in point. The 

 occurrence of piiritana at widely separated points on the Connecticut 

 River is another, for the gravid female could be carried as well by the 

 river current in the one case as by winds in the other. In the case 

 of our maritime species it is equally easy to conceive of the action of 

 tides and storms providing the accidents that assisted in the dispersal 

 of the species. 



Dipping for a moment into the geological history of our conti- 

 nent we find readily enough stupendous accidents that must have pro- 

 foundly influenced the distribution of our tiger beetles. I will refer 

 however to but two, the glacial period and the former connection of 

 this continent and Siberia. 



