SCIENTIFIC COMMITTEE, JUNE 14. 



Xli 



Scientific Committee, June 14, 1904. 

 Dr. Masters, F.R.S., in the Chair, and seven members present. 



Death of B. McLachlan, Esq., F.B.S. — Dr. Masters made a few 

 remarks upon the loss to science occasioned by the death of this eminent 

 member of the Scientific Committee. He was one of the very few left of 

 the earliest members of it, and until failing health prevented him, he was 

 a most regular attendant at its meetings. He was always most courteous 

 and willing to give his assistance whenever questions arose in the 

 department of entomology, in which he was an expert ; the suggestions 

 he made for the treatment of insect attacks were marked by caution and 

 sound judgment. 



Oak Tree "Spangles." — To an inquiry from Purnell Purnell, Esq.. 

 Streatham, as to the origin of these galls, Mr. Saunders, F.L.S., supplied 

 the following life-history : — " They are formed by the grubs of one of the 

 many kinds of gall-flies which infest the Oak. Most of the species, this 

 one (Spathegaster baccarum) among the number, do not complete their 

 life-cycle until they have gone through two generations ; this peculiarity 

 is generally spoken of as ' the alternation of generations.' In the case of 

 the species which forms the galls sent, the flies which are hatched from 

 them are of both sexes ; and, after pairing, the females pierce the under- 

 sides of the leaves and lay their eggs just below the surface. The grubs 

 hatched from these do not form spherical galls, as the grubs of the last 

 generation did, but make the little flat brown galls which are so common 

 on the under- sides of Oak leaves, and are commonly known as 

 1 spangles.' The flies from these galls emerge in the following spring, 

 but, strange to say, in appearance they are quite unlike the flies of the 

 previous generation which laid the eggs ; and there are no males, only 

 females. These 1 parfchenogenetic females ' for many years were known as 

 Neuroterus lenticularis, and were considered to be a distinct species ; they 

 lay their eggs more commonly on the male flowers of the Oak, when they 

 are known ac 1 Currant galls ' on account of their resemblance to a small 

 bunch of Currants ; but they often lay them on the leaves. The life- 

 cycle is now complete, and begins again as soon as the flies emerge. In 

 some species the life-history of the two generations is even more different 

 than that just described, the sexual generation laying its eggs on the 

 roots of the trees, and in due time galls are formed. The asexual 

 generation which emerges from these galls are wingless, crawl up the 

 stems and branches of the trees, and lay their eggs generally in the 

 terminal bud of the shoots ; the galls there formed are the well-known 

 ' Oak-apples,' the flies from which are of both sexes : the males are 

 winged, but the females have only rudimentary wings, or are wingless. 

 The only means which I can suggest for preventing the Oaks from being 

 attacked by the Spathegaster baccarum is by destroying the galls ; this 

 would be almost impossible in the case of the galls formed in the spring ; 

 but the second generation of galls, which remain on the leaves till after 

 they have fallen, may easily be destroyed by collecting the fallen leaves 

 and burning them. If this were done thoroughly, there would be a 



