490 



AMERICAN FORESTRY 



LARGE "APi'LE GALLS" OX LEAVES OF AN OAK 



Fig. 8 These, beautiful green galls are also called "oak galls" and "oak apples;" they 

 are made by a gall-fly called Amfhiholips coccinae. here shown at a in the insert, with 

 a cross giving its actual size. The interior of one of these galls is fibrous. Other oak 

 apples are spongy inside, as seen in Fig. ii. Such oak apples occur on the red-oak or 

 black-oak leaves, while the fibrous ones are confined to the scarlet oaks. The insect shown 

 at h is Aml'hibolips spoiu/ifica. and it produces the spongy oak apples, c (nat. size), an- 

 other species of gall moth (Oclachia yallae-solidaginis), the moth that produces the galls 

 on some of the goldenrods. 



It was at first thought that it 

 was a purely vegetable growth 

 and that the Httle grubs with- 

 in it were the resuh of spon- 

 taneous generation. Later it 

 was supposed that galls were 

 caused by the punctures of 

 insects and the injection of a 

 poisonous liquid. With the 

 true gall-flies, however, the 

 gall apparently does not com- 

 mence to form until after the 

 egg hatches. It is supposed 

 that the larva secretes a liquid 

 which causes the abnormal 

 growth of the plant, the plant 

 cells which are most active in 

 growth and subdivision being 

 directly affected. 



"The egg of the gall-fly is 

 slender, and has a very long 

 petiole which is six to ten 

 times the length of the egg- 

 ])ody, and this is inserted by 

 means of a very long, curious- 

 ly for.ned ovipositor. A good 

 account of the method of ovi- 

 position reported by Riley 

 from observations made by 

 Pergande will be found in the 

 Proceedings of the Entomo- 

 logical Society of Washington 

 (Vol. iii., pp. 260-263)." 



Doctor Howard tells us that 

 "about fifteen hundred species 

 of this super-family have been 

 described," and it must be re- 

 membered that that wag fully 

 twenty years ago, at which 

 time he further remarked that 

 "the full development of none 

 of the American gall-making 

 Cynipods has been studied 

 with the care which this sub- 

 ject should have, and doubt- 

 less there are many interest- 

 ing and important facts yet to 

 be discovered." Be this as it 

 may, Doctor Howard has 

 given us a deal of informa- 

 tion about these extremely 

 curious little insects and their 

 ways, especially in regard to 

 the time of their appearance 

 during the year; on the par- 

 thenogenetic generation which 



..J*. 



