46 OHIO BIOLOGICAL SURVEY 



Hvmoioptcrou; but with it would also be destroyed the parasitic Hy?ne7i- 

 optcron, thus checking by so much the perpetuation of these valuable 

 insects. If this happens it would also make the Syrphidac decidedly inim- 

 ical to these Chalcididae and so, paradoxically, beneficial to the aphids 

 and ants. Fifth, lady-bird beetles ( CoccincUidac) are usually present in 

 the aphid colonies, preying on the aphids. These would have practically 

 the same relation as the larvae of Syrphidae; that is, hostile to the aphids 

 and indirectly so to the ants, the Syrphidac, -zxidi the "p^iXdisiiic Hymmoptera , 

 friendly to the host-plant. Sixth, "Aphis-lions" the larvae of "lace- 

 w' inged or golden-eyed flies' ' {Hemerobiidac) are very frequent visitors to 

 such aphid colonies, and they, too, prey on the aphids. Their relations 

 would be the same as for the CoccincUidac, and in addition they could be 

 considered hostile to the interests of those species. Seventh, spiders are 

 frequently present, especially in the aphid-galls. Their exact relations 

 were not studied but they doubtless prey on some of the insects, and they 

 often nest in the empt}^ pupa cases of the ►S)';7!>/^/«'<a;^. Eighth, L,epidopter- 

 ous larvae and a number of other creatures of undetermined species and 

 uncertain relations were also taken in the Pemphigus galls. 



(4) Hymenopterous parasites of the larvae of Syrphidac themselves 

 are present. These are fully discussed under the heading of "Enemies' ' pp. 

 50. 51- 



(5) Not many larvae are known to feed externally on plant-tissues. 

 Mcsogranima polita is the one conspicuous case and this species, while 

 wide spread, has excited alarm by the feeding habits of its larvae in only 

 a few cases and a few localities. Either they do not often attack corn in 

 large numbers (their larvae probably having other food-plants) or else 

 their attacks pass unnoticed. When the larvae are abundant, the injury 

 is said to be very serious. They feed on the saccharine cells at the base 

 of the leaf-sheaths, causing a wilting and browning of the leaf said to 

 resemble the injury resulting from the attacks of chinch bugs. The lar- 

 vae also eat the pollen grains in the "tassel." While pollen production in 

 most plants, and in corn, is a lavish one and much of it could be lost with- 

 out detriment, yet with great increase in numbers of the larvae it is easy 

 to see how they might become a serious pest of this important crop, b}' 

 interfering with the formation of the grain, to which fertilization is essen- 

 tial. Furthermore this injury might be serious and not noticed until they 

 had done irreparable damage. 



The aquatic larv^ae oi Hclophi/iis A?///';(V/.s- were believed by Dr. Morrey 

 to feed on Confervac or Algae. (See pp. 70, 71.) 



