282 CALIFORNIA ACADEMY OF SCIENCES [Pboc. 4th Sek. 



phum pisi, was unusually abundant, destroying great areas 

 of vetch during June. One of the commonest beneficial in- 

 sects preying on the aphids was the larvae of L. pyrastri. 

 Great numbers of these larvae were collected to study possi- 

 ble parasites. About 3 per cent parasitism was observed. Of 

 the adults emerging about 32 per cent were the melanic 

 forms with black abdomens. A few specimens of unicolor 

 were collected about aphids on "snow balls" in 1915. None 

 has since been observed or collected in the valley, which 

 would tend to substantiate Verral's report of their periodical 

 appearance. Two females, one collected 1907 (Bridwell) 

 and one VIII-' 17 (Lovett) in the Cascades, alt. 6,500- 

 7,000 feet, are smaller, but apparently belong here. In these 

 two the interrupted cross band on the second abdominal seg- 

 ment persist as two elongate dots. 



504. Syrphus abbreviatus (Zett.) 

 Corvallis, IV; Mary's Peak, VI (Lovett). 



505. Syrphus americanus Wied. 

 Common. This species and opinator are two of the most 

 common and generally beneficial forms of Syrphidae feeding 

 on aphids in Oregon. L. pyrastri proves the greatest feeder of 

 all on Aphis carbicolor and Macrosiphum pisi; but on the 

 basis of species attacked and general abundance opinator 

 ranks first with americana a close second. 



506. Syrphus arcuatus Fall. 

 Common, V-VIII. More abundant in higher altitudes 

 2,500 to 5,800 feet. 



507. Syrphus bimaculatus Lovett 

 Mary's Peak, VI-15 (Lovett) ; Mt. Jefferson, VI (Brid- 

 well). 1919, Proc. Cal. Acad. Sci., Ser. 4, IX, p. 244. 



508. Syrphus diversipes Macq. 

 Pamelia Lake; Mary's Peak, VII-VIII (Gentner) ; Lava 

 Lake, VII-25 (Lovett). 



509. Syrphus grossulariae Meig. 

 Parkdale, VI- 18 (Cole) ; Corvallis (Lovett). 



