August, 'OS] 



JOURNAL OF ECONOMIC ENTOMOLOGY 



245 



THE INFLUENCE OF MINIMUM TEMPERATURES IN 



LIMITING THE NORTHERN DISTRIBUTION 



OF INSECTS' 



By E. DwiGHT Sandeksox, ProfC!<sor of Zoology and Entomology, New Hamp- 

 shire College; Director and Entomologist, New Hampshire Agricultural 

 Experiment Station. 



For the past three winters the mortality of the larvae of the brown- 

 tail moth (Euproctis chrysorrhoea) in their winter nests has been 

 determined by my students at different dates. January 24, 1907, 

 the temperature dropped to — 24°F. at Durham, X. H., the lowest tem- 



TABLB 1.2 



^ a 



Locality. 



Date counted. 



* fci m 

 bDtS m 

 =3— d 



Remarks. 



Durham, N. H.. 

 Durham, N. H.. 

 Durham, N. H.. 

 Durham, N. H..' 

 Durham, N. H.. 

 Lewiston, Me.. . 



Bath, Me 



Rockland, Me.. 

 Bar Harbor, Me. 

 Portland, Me ...j 

 Franklin, N.H.. 

 Newton, N. H ..j 

 Nashua, N. H .. 

 Comord,3 N. H. 



Jan.-Mar. 1905 



Jan.-.\pril 1906 



Dec. 12-Jan. 23, 1907 

 After Jan. 24, 1907 .. 

 After Jan. 24, 1907.. 



Mar. 15, 1907 



Mar. 23, 1907 



Mar. 15,1907 



Mar. 15,1907 



Mar. 15, 1907 



Feb. 20, 1907 



Feb. 20, 1907 



Feb. 20, 1907 



Feb. 20,1907 



271 

 248 

 374 

 401 

 922 

 239 

 262 

 325 

 282 

 464 

 336 

 468 

 608 

 342 



13 to 39% dead, 

 etc 90% dead. 



Nests from apple, etc. 

 Nests from tall oaks. 



( Temperature calculated 

 ( from Isotherms of Map 1. 



Large nests on elm, oak. 



lA paper read before the section of Economic Zoology, of the seventh Inter- 

 national Zoological Congress, Boston, 1907. 



^Since the above was written and Map 1 prepared I have received the fol- 

 lowing data through the kindness of Prof. E. F. Hitchings, State Entomolo- 

 gist of Maine, under whose direction the counts of mortality in the nests 

 were made. (See page 246.) 



sNests were also received from Ossipee, N. H., where the temperature must 

 have gone below — 20° F. (see Map 1), in which all the larvae were dead, and 

 no live larvae were found in nests at Ossipee according to a resident there. 



