398 INSECTS INJURIOUS TO VEGETATION. 



legs are dull brownish red ; and the fore-wings have a brown spot 

 near the middle of the outer edge. Its body is nearly one quar- 

 ter of an inch long, and its wings expand five eighths of an inch. 



A dwarf oak (Q^uercus infectoria), growing on the borders of 

 the Dead Sea, produces galls somewhat like the foregoing, which 

 have been supposed to be the apples of Sodom, described by an- 

 cient writers as fruits fair to the view, but crumbling into dust 

 when handled. A late writer,* however, has shown that these 

 tempting and deceptive productions are the real fruits of a tree, 

 the Asdepias procera, resembling our common silk-weed in its 

 botanical characters. 



Clusters of three or four round and smooth galls are often seen 

 on the small twigs of the white oak. They are nearly as large 

 as bullets, of a greenish color on one side, and red on the other. 

 They approach in hardness to the Aleppo galls, and perhaps 

 might be put to the same use. Each one is the nest of a single 

 insect, which turns to a fly and eats its way out, in June and July, 

 having passed the winter as a chrysalis, within the gall, lodged in 

 a clay-colored egg-shaped case, about three twentieths of an inch 

 long, and with a brittle shell. These little cases appear to be 

 cocoons, but are not made of silk or fibrous matter. Similar co- 

 coons are found within many other galls, and I have some which 

 were discovered under stones, and were not contained in galls, 

 but produced gall-flies, the insects having left their galls to finish 

 their transformations in the ground. The gall-fly of the white 

 oak varies in color. Sometimes it closely resembles the gall-fly 

 of our oak-apple, differing from it only in size, and in wanting 

 the brownish spot and dark colored veins on the fore-wings ; and 

 sometimes it is of a dull brownish yellow color, with a brown 

 spot on the back. It is three twentieths of an inch long, and its 

 wings expand three tenths of an inch. It is the Diplolepis, or 

 more properly Cynips, oneratus of my " Catalogue." 



Galls of the size and color of grapes are found on the leaves 

 of some oaks. Each one contains a grub, which finishes its 

 transformations in June. The winged insect is my Cynips nulil- 

 ipennis, or cloudy-winged Cynips, so named from the smoky 



* Robinson's " Biblical Researches in Palestine," Vol. II., p. 235. 



