66 



another storm set in, the temperature falling to 11° F. the following 

 day, but warming the day after that. 



March 15 a storm set in about 6 a, m. with considerable snow fall, 

 most of which remained upon the grass for five or six days, and in 

 protected localities as late as the 24th. March 25 still another storm 

 occurred, during the night, with a lighter fall of snow, followed by 

 finer and clearer weather beginning on the 27th. 



After the first of April winter weather had ceased and spring- 

 begun. 



It would be a matter of some difficulty to define the exact signifi- 

 cance to be attached to the terms Northern forms and Southern forms 

 used in the present and also the earlier article of the writer on the sub- 

 ject under discussion. This matter can be best explained, perhaps, by 

 repeating what has been said in the first article mentioned (p. 53), that 

 the District of Columbia occupies a place, zoologically speaking, in 

 the Carolinian f aunal area nearly midway between its two extremes as 

 at present defined; and the Northern forms are those which develop 

 more freely north of this line, while the Southern attain their greatest 

 increase south of this line. To be more explicit, however, it should 

 be said that the injurious species which will be particularly mentioned 

 as Southern are believed to be truly Austro-riparian, while the North- 

 ern species belong rightfully to the Alleghanian area of the Transition 

 zone and the most northern portions of the Carolinian or upper Austral 

 life zone. At least two species which it was found impossible to assign 

 to either the Northern or Southern group, the writer believes, as a 

 result of his study during the past season, have now been correctly 

 placed. They are the fall arnry worm, which must be considered a 

 Southern form, although it finds its way quite far northward, and the 

 destructive green pea louse, which rightfully belongs in the Northern 

 group. 



OCCURRENCE OF SOUTHERN FORMS OF INJURIOUS SPECIES IN 1900. 



Of the fifteen injurious forms of insects mentioned by the writer 

 (loc. cit., pp. 55, 56) as unusually scarce in the neighborhood of Wash- 

 ington in 1899 several species showed marked increase. To mention 

 these all in the same category, the list includes four species which were 

 not seen at all the previous year. These are the pickle worm, Mar- 

 garonia nitidalis, and the melon caterpillar, M. hyalinata, each of 

 which was abundant in one locality only; the cabbage pionea, Pionea 

 rimosalis, which was eveiywhere numerous and quite destructive 

 throughout the season, and the garden webworm, Loxostege similalis, 

 which was several times observed during September. 



The Northern leaf -footed plant-bug, Leptoglossus oppositu-?, was gen- 

 eral lv abundant and was very troublesome, something never before 

 noticed in this vicinity, 



