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. 70), is extremely injurious to wheat 



FIG. 69. Plant galls produced by Hemiptera and Diptera. 1. Pine-apple gall 

 on twigs of the spruce fir produced by the spruce-gall Aphis (C'herines 

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

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

 one of the Hemiptera. 3. Covering galls on an ash leaf (Fraxinus excelsior) , 

 produced by Diplosis botularia (Diptera). 4. Covering gall on Pistacia 

 (Pistacia lentiscus), produced by Pemphigus cornicularius. 5. Solid galls 

 on the cortex of Duvana lonyifolia, produced by Cecidoses eremite (Hemip- 

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

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

 cerris. 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." 



