160 SCHOOL ENTOMOLOGY 



worm (Isosoma tritici), and the Wheat Straw-worm (I. 

 grande) are both more or less serious pests to the 

 wheat crop. Other species feed on seeds of plants before 

 they ripen. One Chalcidid is beneficial because of its 

 habit of feeding on figs of certain sorts. The structure of 

 the fig is such that for cross-fertilization the presence of 

 this insect (Blastophaga grossorum), is necessary. The 

 females of the insect carry pollen from fertile blossoms of 

 the "caprifig" to the infertile blossoms of the valuable 

 Smyrna fig. The insects breed in the " caprifigs " and 



FIG. 117. Wing of Hymenopterous Insect. Letters indicate names 

 of the cells and of the veins on the anterior margins of the cells. 



c, costa; Sc, sub-costa ; R, radius; M, median ; Cu, cubitus ; \" A, first anal; 

 2" A, second anal; 3" A, third anal; s, stigma. 



merely visit the Smyrna figs while in search of suitable 

 places for egg laying, but, as they often, in mixed groves, 

 come from the pollen-bearing flowers, they carry pollen 

 with them and in their activities within the infertile sorts, 

 dust this into their flowers. The process is called "cap- 

 rification." The discovery of the above facts and the 

 importation and colonization of the Blastophaga in south- 

 ern California has enabled growers there to produce 

 Smyrna figs of the best quality where they were formerly 

 unable to compete with the imported product. It serves 

 as an example of the extremely varied problems connected 

 with the science of entomology. 



