228 THE ENTOMOLOGIST. [Jan. 



to exercise their building propensities on roses, potentillas, brambles, 

 and other bushes. But observers watching these makers of galls 

 on the oak have Ijeen struck with two facts — namely, that different 

 insects come out of the galls with the rolling seasons of the year ; 

 and along with this, that different galls appear on the same tree. 

 The researches, specially, of ilr. Walsh and Dr. Alder have gone to 

 show that these phenomena can be explained by the same insect 

 having two methods of reproduction, thereby exercising tlie function 

 of dimorphism, or appearing in two forms. The earlier brood is 

 the result of ordinary sexual intercourse, while the later one springs 

 from the parent by a process of budding. 



The local characteristics of galls on the same tree, so long well 

 known, appear to have some connection with this curious function, 

 and is therefore worthy of illustration. The brown oak spangle, 

 which is seldom ever met with on any part of the leaves, appears 

 in September. Many galls, like the artichoke gall, are exclusively 

 confined to the bud ; whereas the currant galls found in the 

 months of May and June are got not only on the lower surfaces of 

 the leaves, but also above, usually confining themselves to the 

 male inflorescence. Some galls appear in the spring or early 

 summer, and the insects emerge from them usually in ]\Iay, June, 

 and July. Autumn galls become developed before winter, during 

 which they are found, fallen from the tree, on the ground, where 

 they increase in size, after which the insects emerge at latest in the 

 early spring. ISTo two broods of a gall have come out in the same 

 summer. From the spring galls insects emerge in July. AVhence 

 then the insects thus without images of the subsequent season? 

 Thus, the currant galls of the oak cannot have been formed at the 

 time of the flight of the gall-flies of the previous year ? So, too, in 

 regard to the autumn " oak spangles " ? The result of experiments 

 either on young oaks in pots, or of galls placed on the branches of 

 mature trees, but carefully covered with wire gauze so as to prevent 

 the escape of the insects under observation, has led observers to the 

 conclusion that the liroods issuing, for instance, as in the suliject of 

 our illustration, iu June and October are the products of two kinds 

 of reproduction as already described. The ovipositors of the young 

 insects appear to have a peculiar function in relation to the different 

 oak galls, also varying with the season. 



At the first sale of the Califoruian redwood in London, the price 

 per foot cube for plants averaged fully 3s. 6d., against an average of 

 2s. lOd. at the Glasgow sale. The whole of the lots were sold. 



