THE DICTIONARY OF GARDENING, 



Oak G&Ua continued. 



and very juicy, are common, in May and June, on the 

 lower surfaces of leaves, and on catkins, where they 



FIG. 707. OAK GALLS. 



A, Galls of Neuroterus lenticularis (Oak Spangle Galls)!, On 

 Lower Surface of Leaf ; 2, Removed from Leaf ; 3, Flat Section, 

 showing round Chamber in centre where the Larva lives ; 4, 

 Transverse Section, in autumn, showing Form while still on 

 the Leaf, with very small Chamber ; 5, Transverse Section 

 of Gall in following spring, showing changed Form and 

 much larger Chamber. (Nos. 4 and 5 are about four times en- 

 larged.) 



B, Galls of Spatheyaster baccarum (Currant Galls of Oak) 1, Upper 



Surface of Leaf, showing Galls projecting through ; 2, Lower 

 Surface of Leaf, showing three (Jails, of which the Upper is 

 cut through to show the Larval Chamber; 3, Male Catkin 

 bearing Galls. (All the figures are a little smaller than natural 

 size.) 



look like bunches of Currants (see Fig. 707). The insects 

 (Spathegaster baccarum) are easily reared from these Galls, 



FIG. 708. OAK GALLS. 



A, 1, Galls of Dryophanta Jolii on Lower Surface of Oak Leaf, 

 slightly smaller than natural size ; 2, Transverse Section, 

 showing Larval Chamber. 



C, 1, Galls of Sr>athegaster Taschenbcrgi on a Young Twig, natural 

 size ; 2, Gall enlarged. These Galls are violet, with a velvety 

 surface, are soft, and are eaten by the larva till the wall becomes 

 very thin. They appear in May and June ; and, though not 

 recorded from Britain, are believed to be the Galls that complete 

 the cycle with those of Dryopttantaj'oUi. 



if the latter are collected when fully mature, and pre- 

 vented from becoming either too dry or mouldy. Dryo- 



Oak Galls continued. 



phanta folii produces a globular Gall on the backs of leaves. 

 It may reach Jin. in diameter, but the central chamber is 

 small, the walls being thick, though soft and spongy. The 

 surface becomes yellow and red. See Fig. 708. Dryo- 

 phanta divisa also forms Galls on the lower surface of 

 leaves, but the Galls are generally flattened, oval bodies, 

 much smaller than the last-named, with harder, but 

 thinner, walls. They are also more abundant through- 

 out the country. Oak Spangles are among the most 

 curious of Oak Galls. They occur on leaves, almost always 

 on the lower surface. Three kinds have been distin- 

 guished in Britain, agreeing in being circular, about 

 iin. across, and, while on the leaf, quite thin, though 

 bearing a very slight prominence in the middle. The 

 commonest is covered with rusty brown hairs ; it often 

 nearly covers leaves. See Fig. 707. Of the other two, 

 one bears similar scattered hairs, and has the margin 

 turned up ; while the third is green or purple-red, and 

 smooth. All are the work of insects belonging to the 

 group Neuroterus, and which are named N. lenticularis, 

 N. Iceviusculus, and N. fumipennis. Another species of 

 this genus (N. numismatis) makes Silky Button Galls, 

 so called from their resemblance to tiny, round, flattened 



FIG. 709. OAK GALLS. 



A, Galls of Neuroterus numismatis (Silky Button Galls of Oak) 



1, Lower Surface of Leaf, bearing many, about natural size ; 



2, Gall showing the depressed Surface, enlarged; 3, Gall 

 seen from the side ; 4, Gall in Section, showing small central 

 Chamber for Larva, hollow Border cut through at each side, 

 and short Footstalk. 



B, 1, Three Galls of Spathepaster vesicatrix (Blister Galls of Oak 



Leaves) in a Leaf, natural size ; 2, Transverse Section of Leaf, 

 with Gall, showing very small Larval Chamber. 



buttons, covered with brown silk threads (see Fig. 709). 

 These Galls are often formed in myriads on the lower 

 surface of the leaves, so as, in some cases, to cover 

 it almost entirely in autumn. Yet another Gall, of 

 very frequent occurrence, is so inconspicuous as to be 

 easily overlooked in the leaves, in which, during June, 

 it looks like a mere low blister, about gin. across (see 

 Fig. 709). The insects reared from these Galls have 

 been named Spatheyaster vesicatrix. This may be called 

 the Oak Blister Gall. 



In acorns, at times, Galls are to be found in the 

 seed, though the outside of the acorn shows no sign 

 of insect work. The interior is broken up by nume- 

 rous small oval spaces, in each of which lives a small 

 larva of the Gall-maker (Andric.us glandium). 



These brief notes must suffice for the more common 

 forms of Oak Galls ; and attention must now be directed 

 for a little to certain points in the life of the Gall-makers 

 points which, for a considerable time, seemed to defy ex- 

 planation, but which are gradually emerging into the light, 

 thanks to the careful experiments and observations of 



