October, '16] DAVIDSON: SYRPHID.E IN CALIFORNIA 457 



Paragus tibialis Fallen and P. obscurus Meigen, whether considered 

 as two valid species or as two varieties of a single species, are common 

 flies. The adults are small shining black or reddish-black flies. The 

 larvae are aphidophagous; that of tibialis, according to INIetcalf (Ohio 

 State Univ. Bui. XVII, 31) is light yellowish-brown. The small size 

 of these species rather militates against their economic importance. 

 The larvae feed on aphidids attacking such semi-aquatic plants as dock. 



Of all these species mentioned above the most important economic- 

 ally are in order probably Catabofnba pijrastri, Syrphus opinator, S. 

 americanus, S. arcuatus, Allograpta obliqua, and Eupeodes volucris. 

 The first named probably outweighs all the others together. 



In California syrphid larvae are frequently the victims of Ichneu- 

 monid parasites belonging to the genera Bassus, Syrphoctonus, Hom- 

 otropus and perhaps others. They are also parasitized by Chalcids. 

 At times large numbers of the adults are destroyed by fungi, one such 

 outbreak being noticeable in the spring of 1914, in central California. 



Two injurious species of Syrphidce have recently been found in 

 California and both are importations from Europe. The Narcissus 

 bulb-fly {Merodon equestris Fabr.) is apparently now established in 

 central California and Eumerus strigatus Fallen, said to be injurious 

 to onion bulbs in Europe, has apparently become established in the 

 San Francisco Bay region. Both of these species have been taken on 

 the wing on several occasions. Their larvae dwell inside the bulbs 

 and may cause their destruction. Merodon equestris is a large hairy 

 robust fly somewhat resembling a bumblebee while Eumerus strigatus 

 is a small, black shining, almost bare, species. Copestylum marginatum 

 Say and species of Volucella in their larval stages inhabit the interior 

 of cactus leaves and stems and may cause injury to the host (Cf. 

 "Principal Cactus Insects of United States," W. D. Hunter, F. C. 

 Pratt, J. D. Mitchell, U. S. D. A., Bui. 113, 1912). 



Chairman H. J. Quayle: This paper is now open to discussion. 



Secretary: The following communication from H. E. Burke re- 

 garding this paper has been received and is as follows: 



"I would be glad to be there at the discussion of Mr. Davidson's 

 paper to call attention to the damage done by the larvae of some forest 

 Syrphidce to our timber. The larvae (bark maggots) of Cheilosia 

 and probably other genera cause serious defects (black checks) in the 

 wood of much of our white fir (Abies concolor), red fir {Abies magnifica) 

 and hemlock {Tsuga heteropJujlla) . In most discussions of the Syrphidce 

 the injurious habits are not given." 



Chairman H. J. Quayle: The next paper by G. F. Moznette will 

 be read by the secretary. 



