38 The Ohio Journal of Science [Vol. XVI, No. 2, 



There are three groups of zoocecidia occurring on hickory 

 trees : 



1. Galls formed by species of Eriophyes (Fam. Eriophyidae 

 of the Acarina or mites), or an allied genus. Only two are 

 known. 



2. Galls induced by species of Phylloxera (Aphididae of the 

 Hemiptera). Pergandef has presented an excellent survey 

 of these insects accompanied by very satisfactory descriptions 

 of the cecidia formed by them. 



3. Galls caused by species of Caryomyia (Itonididas of the 

 Diptera). Possibly other genera may be represented on the 

 hickories, but according to Felt J "most of the hickory leaf 

 galls are probably made by species of Caryomyia, though 

 other midges have been reared from these deformities. " 



The genus Caryomyia, which undoubtedly occupies an 

 important place in relation to the majority of the galls described 

 in the present paper, will be given special consideration. Felt, 

 to whom American cecidology is heavily indebted for his 

 extensive studies of dipterous cecidozoons, presents the following 

 description of the genus Caryomyia in the same citation as 

 that immediately above. 



"Allied to Hormomyia, but differing by the thorax not 

 being greatly produced over the head and by the presence of 

 but 14 antennal segments. The males may have the flagellate 

 antennal segments binodose or cylindric and subsessile and 

 invariably with three low, stout circumfili. The antennal 

 segments of the female are cylindric and with two circumfili; 

 palpi tri- or quadri-articulate; wings rather broad, the third 

 vein joining the costa at or near the wing apex; claws simple, the 

 pulvilli well developed. The ovipositor of the female is short 

 and with minute lobes apically. The genus appears to be 

 confined to hickory leaf galls." 



Adult insects not technically known are given the old 

 generic name " Cecidomyia. " 



These galls as well as similar ones on other kinds of plants 

 arise as the result of some stimulus (the nature of which is still 

 not definitely known) applied by the very young larva to the 



tPergande, T. "North American Phylloxerinae affecting Hicoria and other 

 Trees." Proc. Davenport Acad. Sci. 9:185-271, pis. 1-21. 1903. 



$Felt, E. P. "The Identity of the better known Midge Galls." Ottawa 

 Naturalist, Vol. 25, Nos. 11, 12. 1912. 



