13 



Hyaloptenis arundinis, F., on prune and plum ; Aphis rumicis, L., on 

 beans ; Aphis medicaginis, Koch, on leguminous crops ; Acyrthosiphon 

 {Macrosiphion) pisi, Kalt., on peas ; Aphis brassicae, L., on cruciferous 

 croip&; and Chroma phis juglandicola, Kalt., on walnuts — have been 

 accompanied by their Svrphid enemies, the most important being 

 Lasiophthicus {Ca(abomba) pyrastri, L., which has been extremely 

 abundant in central California in those years in which there has been 

 severe infestation by Aphids. This species appears early in March, 

 when oviposition takes place among colonies of winter-feeding Aphids, 

 such as Macrosiphum rosae, L. , on roses, and M. solanifolii, Ashm. , on 

 weeds like Erodimn. At the end of this month eggs are laid among 

 young colonies of orchard-infesting Aphids, the stem-mothers of which 

 hatch from the winter eggs in February and early March. Other 

 Syrphids which attack injurious Aphids in appreciable numbers are 

 Syrphus ribesii, L., S. torvus, 0. S., S. americanus, Wied., S. opinator. 

 Will., S. arcuotus, Fall., and Eupeodes volucris, 0. S. Of these, 

 S. americanus and *S. opinator are the two most abundant and beneficial. 

 S. arcualus occurs in early spring in the larval stage on conifers, and 

 later principally on apples, on which it attacks Aphis malifoliae. Fitch. 

 Sphaerophoria melanosa. Will., and S. sulphuripes, Thom., are also 

 aphidophagous in the larval stage, the pupae commonly occurring 

 on the plant on which the larvae have been living, differing in this 

 respect from the previous species. AUograpta obliqua, Say, preys 

 upon Aphids on citrus and truck crops in Southern California. Further 

 north it is less common and has been bred from the walnut aphis, 

 Chromaphis jiiglandicola, Kalt. A. fracta, a rarer species, is pre- 

 sumably also aphidophagous. The economic importance of Mesograpta. 

 geminata, Say, and M. niarginata. Say, is unknown, while the eastern 

 M. polita, Say, is injurious to maize, sometimes causing considerable 

 damage. The larvae of Baccha lemur, 0. S., have been bred from 

 Pseudococcus citri, Risso, and other mealy bugs in Southern California. 

 Elsewhere other species of Baccha have been reported as preying in 

 the larval stage on Aphids, Coccids, leaf-hoppers and whitefiies. 

 Pipiza pisticoides, Will., and P. albipilosa, Will., are both common in 

 Cahfornia, their larvae feeding on Aphids such as Pemphigus popu- 

 licaulis, Fitch, on poplar. P. modesta, Lw., and P. radicum, Walsh 

 & Riley, occur in the east upon Eriosoma hnigerum, Hans., and the 

 latter also preys upon the grape phylloxera {Phylloxera vitifoliae). 

 Paragus tibialis, Fall., and P. obscurus, Mg., are common and their 

 larvae are aphidophagous, but their small size militates against their 

 being of economic importance. 



Two recently imported injurious Syrphids are Merodon equestris, F., 

 (narcissus bulb-fly) and Eumerus strigatus, Fall., which infest onions 

 and other bulbs. Copestylum marginatum. Say, and species of Volucella 

 in their larval stages inhabit the interior of stems and leaves of cacti. 



Syrphid larvae are often parasitised by Ichneumonid parasites 

 belonging to the genera Basstis, Syrphoctonus and Honiotropus, as well as 

 by Chak ids, and at times large numbers of adults have been destroyed 

 by fungi in central California. 



In the discussion following this paper, a communication was read 

 from Mr. H. E. Burke drawing attention to the damage done to white 

 iir {Abies concolor), red fir {Abies magni-fica) and hemlock {Tsuga 

 heterophylla) by the Syrphid genus Cheilosia, in the larval stage. 



