68 



ZOOLOGY 



or galls are produced. The galls are formed only in grow- 

 ing tissue such as the tips of branches, buds of flowers or 

 growing leaves, and are less striking on the whole than the 

 galls of Hemiptera (Fig. 69). A certain kind of gall-fly, 

 called Hessian-fly (Fig. TO), is extremely injurious to wheat 



FIG. (>'-.). -- Plant galls produced by Hemiptera and Diptera. 1. Pine-apple 

 on twigs of the spruce fir produced by the spruce-gall Aphis (U/iennes 

 abretis, one of the Hemiptera). 2. Covering gall on the petiole of the pyra- 

 midal poplar (Populus pyramidalis), produced by Pemphigus burxarius, 

 one of the Hemiptera. :>. Covering galls on an ash leaf (Fraxinus excelsior) , 

 produced by Diploxi-t bnftdaria (Diptera). 4. Covering gall on Pistacia 

 (Pisfacia lentiscu.fi}, produced by PenipJiif/ii* rornii'tdarhifi. 5. Solid galls 

 ou the cortex of Dnvana lonyifolifi, produced by Cecidoxes eremite (Hemip- 

 tera) . (>. Longitudinal section of one of these galls. 7. Capsule galls on the 

 leaf of the turkey oak (Quercus cerris, Hemiptera), produced by Cecidomyia 

 cerri*. 8. One of these galls cut through, with the operculum still firmly 

 attached. 9. The same, with the operculum falling away ; X 3. The remain- 

 ing figures natural size. From Kerner, " Pflanzen Leben." 



