THE CANADIAN ENTOMOLOGIST. 31 



SOME PLANT-LICE AFFECTING PEAS, CLOVER, AND 



LETTUCE.* 



BY E. DWIGHT SANDERSON. 



Nectarophora pisi, Kalt., and varieties. 



The " Green Dolphin " is one of the best-known pests of peas and 

 vetches in Europe, though but little concerning its economy has been 

 recorded by European writers. In this country, A r . pisi, Kalt., has been 

 noted by Thomas 1 , Oestlund 2 , and Williams 3 , but as their specimens were 

 never compared with any from Europe, and as plant-lice are exceedingly 

 variable and descriptions of them are, therefore, often of but little value 

 even when accurate, the identity of their specimens with the European 

 forms has been somewhat in doubt. 



At the beginning of the present outbreak of the pest in the spring of 

 1899, as specimens of N pisi of both American and European authors 

 were unavailable for comparison, and as most of the European writers 

 described the species as very much smaller than the remarkably large form 

 under consideration, the species was named Nectarophora destructor by 

 Prof. W. G. Johnson*, and described by him as new 5 . Prof. Johnson 

 gives* Mr. Th. Pergande as authority for the species, stating that he 

 li considers it an undescribed species," and adds, " Inasmuch as Mr. 

 Pergande does not care to describe ic, it is my privilege to name the 

 insect." 



In Dec, 1899, tne attention of the writer was called to a species of 

 Nectarophora doing serious injury to lettuce under glass. Careful study 

 tailed to reveal but a few minor characteristics by which this species 

 could be separated from N destructor, Johns., the chief difference being 

 its smaller size, but many specimens were as large as small destructor. 

 The similarity of this aphid to destructor led to a study of the plant-lice 

 infesting lettuce foliage, and also of the variation in size, form and colour 

 of N. destructor, taken at different times during 1899 and 1900. The 

 following table gives the average measurements of different series of 

 specimens of destructor, those of N. pisi, Kalt., as given by various 

 authors, and those of N destructor as described by Prof. Johnson. 

 Numbers 3, 4, 5, 11, 17, 20, 21 and 22 are all unquestionably N. 

 destructor, Johns. : 



(*From the Entomological Dept. of the Delaware College Agricultural Experiment 

 Station, Newark, Del.) 



1 Thomas, 8th Rept. St. Ent., 111., p. 64(1879). 



2 Oestlund, Bull. No. 4, Geol. and Nat. Hist. Surv., Minn., p. 82 (1S87). 



3 Williams, Spec. Bull. No. 1, Univ. Nebr., Dept. Ent., pp. 6, 9, iS, 20, 23 (1891). 



4 W. G. Johnson, Bull. No. 20, n. s., Div. Ent., U. S. Dept. Ag., pp. 94-9 (1899). 



5 W. G. Johnson, Canadian - Entomologist, XXXII., pp. 55-60 (Feb., 1900). 



