TWO SPECIES OE MACROSIPHUM.. 83 



Specimens as varieties of N. pisi Kalt. A larger series and 

 further observation of their Hfe histories may reveal specific 

 distinctions. The present account is published merely to show 

 the extreme variability of this species (or, as it may prove to 

 be, the likeness of several species), and the necessity of a care- 

 ful study of it and allied species." 



The purpose of this present paper is merely to add one more 

 chapter toward the interpretation of two similar species, a chap- 

 ter that seems necessary in connection with the biological and 

 food plant data of these species which is needed before the 

 economic status of these insects can be clearly understood. In 

 regard to the need for further host plant data Mr. Chittenden 

 (1909) writes: 



"The subject of alternate host plants is an important one, 

 since the pea, being an annual, is not available as food for this 

 aphis during the winter. It is desirable to ascertain all of the 

 host plants of the pea aphis, and more especially the weeds, 

 as some one or more of these may be factors of importance in 

 the life economy of the species. It might be necessary in the 

 future, should the depredations of this insect increase, to limit 

 the growing of clover and other legumes, as well as their alter- 

 nate host plants, if such be found, in the vicinity of pea fields. 

 If all of the principal alternate plants could be discovered this 

 might furnish a solution of the problem of how to deal with 

 the insect." 



The futility from an economic standpoint of compiling a 

 series of host plants for a "composite species" is apparent. 



The descriptions of destructor in the Bibliography appended 

 with especial reference to the beautiful figures (Folsom 1909) . 

 in the Illinois Report are still easily available and suffice, to- 

 gether with Miss King's figures of the cornicles in this present 

 paper, sufficiently to characterize the Destructive Green-Pea- 

 louse. The imbrications of the cornicles extend clear to the 

 tip in both apterous and alate forms, there being no terminal 

 area of reticulation as is the case in solanifolii. 



This imbricated character of the destructor cornicle holds 

 good in forms much diversified as to color and size, as both 

 pink and green varieties are alike in this structure. It also 

 holds good for the progeny individuals transferred from pea 

 to shepherd's purse and clover. The distinctions between the 



