260 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



tions occur only iu JNIichigan, Massachusetts, New Hampshire and 

 southwestern New York. The average-anuual-minimum isotherm of 

 — 15°F. corresponds much more closely with the northern limit of 

 this species than the upper Austral as given, with the exception of 

 northern ^Michigan and Ontario, but approaches the limit of the scale 

 much better in Iowa and Nebraska, which are wholly within the upper 

 Austral, but where the scale is practically unknown. The annual- 

 minimum temperature of its native home in China is about 5°F., 

 according to Bartholomew's Physical Atlas, Vol. Ill, Meteorology, 

 Plate II. 



Based upon the data given by ]\larlatt^ concerning the life history 

 of the scale, there can be two generatiims in southern New Hamp- 

 shire, with an effective temperature of 1570°F. over 53 °F., a single 

 brood requiring 600°F. over 53°F. at Washington, D. C, and repro- 

 duction commencing at both points when the mean is about 63° F., — 

 at Washington ]\Iay 15. at Nashua, N. H.. about June 15. Two gen- 

 erations occur in southern New Hampshire according to our observa- 

 tions. 



The Asparagus Beetle (Cnoceris asparagi) was first imported near 

 New York City. It occurs in southern New Hampshire, but is very 

 rarely injurious, often dying out for several years. Chittenden re- 

 cords that it was introduced and comjiletely died out at Rock Island, 

 111., many years ago. Its northern limit agrees quite closely with the 

 average-annual-miuimum isotherm of al)out — 10°F. (see map 3). It 

 occurs in southwestern New York and northeastern Ohio in the tran- 

 sition. Doctor Chittenden- quotes C. W. Prescott of Concord. IVIass., 

 as stating that "innnense numl)ers are killed in winter during se- 

 verely cold spells following open weather" and states that the beetles 

 are quite susceptible to low temperatures. Indeed Doctor Chittenden^ 

 definitely attributes the limitation of the northward spread of this 

 insect to "cold snaps." At Washington, D. C, the beetles emerge 

 from hibernation in April with a mean of about 55°F. The life 

 cycle fr(mi egg to adult occupies three weeks, or an effective temper- 

 ature of 420°F. over 55°, or 300° over 60° F. at Washington, yet it is 

 not common at Durham. N. H., though 1119° over 55° and 525°F. over 

 60°F. are available. 



The distribution and data concerning the life history of the Elm 

 Leaf Beetle (Galerncella luteola ]\Iiill. ) practically duplicate that 

 given for the asparagus beetle and do not need to be enumerated here. 



iBulletin 62, Bureau of Entomology. 

 ^Yearbook U. S. Dept. of Agr. 1896, p. 347. 

 sBulletin 22, p. 63, note. 



