10 BULLETIN 90, U. S. DEPARTMENT OF AGRICULTURE. 



HEAT. 



During the early part of April, 1910, when the aphis was very abun- 

 dant on the roses throughout the entire city of Los Angeles, three or 

 four very hot days occurred during which the temperature rose as high 

 as 100° F., and within a day or two thereafter the numbers of this 

 aphis had become very much diminished. After this it did not seem 

 to occur in large numbers again until about the middle of August. 



BIRDS. 



On March 19, 1910, the writer, with field glasses, watched a white- 

 crowned sparrow (Zonotrichia leucophrys leucophrys) on a rosebush^ 

 10 feet away, eating the rose aphides as fast as it could pick them 

 from the bush. This was continued for fully 10 minutes, during which 

 time many hundreds must have been eaten, as the plant was almost 

 cleaned up by this bird. 



On March 30, 1910, a California house finch {Carpodacus mexicanu 

 frontalis) was observed by the writer eating this aphis from a rose- 

 bush for fully 15 minutes. 



PARASITIC INSECT ENEMIES. 



There are many different species of parasitic insect enemies that 

 attack aphides, and some of these will attack the rose aphis. On 

 June 13, 1910, many specimens of Macrosiphum rosse were found 

 which showed signs of parasitism by an undetermined insect. These 

 aphides were rounded and fastened to the underside of the rose leaves. 

 The parasite when full grown had killed the host and, cutting its way 

 out beneath the body, spun a tiny cocoon between it and the leaf. 

 Unfortunately all of the parasites failed to emerge. While the para- 

 site was not rare, at least during the past year, it did not seem to 

 check the rose aphis to any extent. 



Ephedrus incompletus Prov., a braconid, was reared by the writer 

 from this aphis at Washington, D. C, in 1912. 



PREDACEOUS INSECTS. 



Among the predaceous enemies the larvae of syrphus flies and lady- 

 birds were observed feeding on the rose aphis, and without a doubt 

 the most important check to this insect in 1910 was due to the larvae of 

 syrphus flies. While these did not seem able to clear a plant alto- 

 gether, still it was many times observed that strong thriving colonies 

 of 50 to 60 aphides or more would be reduced by these insects in one 

 or two days to a mere scattering here and there. During the year 

 1910 five different species of Syrphidse were reared from larvae feeding 

 on Macrosiphum rosx. These were Syrphus rlbesii L. (fig. 3), Syrphus 

 opinator O. S., Allograpta fracta O. S., Eupeodcs volucris O. S. (fig. 4) 

 and Lasiophthicus pyrasti L. 



