OBSERVATIONS. 



2T 



The Oak and its Galls. 



Of all our forest trees the Oak 

 seems to offer the greatest attraction 

 to a grouj) of insects, known by the 

 name of Gall-flies (Cynipes) and be- 

 longing to the order Hymenojptera. 

 Koot, stem, buds, leaves, leaf-stalks, 

 catkins, — all offer a home and 

 nourishment to one or other species 

 of Cynips. In some instances the 

 gall is tenanted by a colony, in others 

 by a solitary individual. The eco- 

 nomy is the same in all cases : the 

 parent insect pierces with her ovi- 

 positor that part of the tree best 

 adapted to the nourishment and 

 development of her offspring : the 

 sap stagnates, and causes the part to 

 assume those singular growths, some 

 of which must be familiar to all who 

 have gathered oak-branches on the 

 99 th of May. These grow^ths are 

 destined, as I have said, to nourish 

 and protect the infant progeny 

 through the earlier stages of its 

 existence, until it assumes wings and 

 leaves its home. 



I have had opportunities of seeing 

 the home and watching the develop- 

 ment of several species of Cynips, 

 during my long residence in this 

 neighbourhood, and I give the result 

 of my observations for the benefit of 

 your readers. I shall begin with the 

 root. Tuber-like galls, attached by 

 small threads to the main root, are 

 tenanted by a little colony of gall- 

 grubs. I have not yet succeeded in 



hatching this species, but I hope to 

 do so before the summer. Oak- 

 apples, as they are commonly called, 

 are the nidus of a numerous colony 

 of gall-flies, which find their food and 

 shelter therein in the larva state of 

 existence. These I have repeatedly 

 hatched, as many as twenty or thirty 

 being inhabitants of the same gall. 

 Then we have the round hard galls, 

 round as a marble, on the branches 

 of young oaks. In these single gall- 

 flies pass their earlier existence. 

 The fly somewhat resembles the one 

 that is instrumental in forming the 

 ink-galls on the Quercus infectoria of 

 Turkey and the Levant, but is not 

 so large. The gall, too, bears some 

 slight resemblance to the ink-gall of 

 commerce. The gall on the under- 

 side of the leaves is of a pulpy 

 nature, and is prettily tinted in the 

 autumn with various shades of red 

 and green. This again is the home 

 of a single cynips, which difl'ers in 

 size and colour from that of the 

 hard gall. The leaves of the oak 

 are dotted on the underside with 

 rosy spangles in the autumn that 

 look like parasitic fungi ; these 

 prove to be the home of a single 

 cynip>s. As the leaves fall and fade 

 the spangles become covered with a 

 woolly substance, and in the follow- 

 ing spring they give birth to a small 

 black cynips that really seems dis- 

 proportionate to its tiny home. I 

 have hatched several of these during 



