442 



NA TURE 



[September io, 1908 



This part of the work we shall hope to see thoroughly 

 revised in a future edition. The figure (lo, p. 9) of 

 typical mouth parts of insects is very poor, and the 

 figure (2, p. 4) of the eggs of the lackey moth are 

 certainly not typical of that insect, if they are the 

 eggs of it at all. Several other figures in this section 

 are also very unsatisfactory, such as Fig. 3, showing 

 typical forms of larvee ; in this latter we see no 

 caterpillar, no sawfly larva, and those that are shown 

 are very unnatural. The first chapter deals with the 

 Eriophyidae or gall mites. The more common species 

 that we find in woods and forests have their galls 

 figured. In reference to the literature consulted and 

 quoted, it is a pity the most important writings on 

 the big-bud mite of Lewis and of Warburton are 

 not mentioned. 



There are two chapters on Coleoptera, the first 

 dealing with chafers, long-horns, and weevils, in- 

 cluding the troublesome pine weevils (Hylobius 

 abietis) and the two Pissodes ; we should like to have 

 read a good deal more concerning these and the de- 

 structive beech Orchestes (Orchestes fagi). 



The second chapter, of forty-five pages, deals en- 

 tirely with bark beetles (Scolytidse). The wood sculp- 

 turing of these destructive insects is shown by means 

 of photographic reproductions. This part of the book 

 is nearly complete, and alone makes it of value to 

 the forester. 



Pages 130 to 163 deal with oak galls formed by the 

 Cynipidas, and the chapter contains a useful synoptic 

 table. Chapter v. deals with sawflies, including de- 

 scriptions of the injurious pine sawflies (Lophyrus pint 

 and L. rufus) and the large larch sawfly (Nematus 

 erichsoni); the same chapter contains all that is 

 essential for the forest student on the Siricida or 

 wood wasps and the strange Megastigmi, parasitic 

 on the seeds of the Douglas and silver firs. 



Scale insects or Coccidse form the subject of 

 chapter vi. ; the more important forest species are 

 brielly described, including the ash scale {Chionaspis 

 salicis) and the felted beech coccus (Cryptococcus 

 fagi). Nothing is said about the great harm done 

 by the former, or any suggestions as to how we may 

 easily check its ravages. Regarding the felted beech 

 coccus, the author writes : — 



" A most interesting remedial measure has been 

 brought under my notice at Blagdon, in Northum- 

 berland. With an inch auger bore three holes at 

 about equal distances right into the centre of the 

 trunk about three feet from the ground and sloping 

 slightly towards the root of the tree. Into those holes 

 fpla_ce] as much ' flowers of sulphur ' as can be con- 

 veniently got in and then cork them firmly up with a 

 plug of soft wood. This should be done' in autumn 

 and will be found successful." 



We may point out that this has been tried frequently, 

 and the coccus has not been affected in the least, 

 except about four inches around the auger holes ! 

 A comparatively small number of Lepidoptera are 

 described in chapter vii., but some of the more im- 

 portant ones are mentioned, such as the goat moth, 

 vapourer, winter moth, oak tortrix, pine shoot tor- 

 trix, larch coleophora, and the new larch pest, 

 Argyresthia lacvigateUa. The chapter on aphides, 

 NO. 2028, VOL. 78] 



a family of insects at present little understood, con- 

 tains an account of the pine chermes, six species 

 being detailed and their general effects well illus- 

 trated. The recent valuable work of Borner ' will, 

 however, have to be included in a subsequent edition. 

 Naturally, Diptera take up only a few pages, mostly 

 on gall-flies or Cecidomyiida, which cause various 

 deformities or galls on leaves, buds, wood, &c. 



Several Psyllidae are detailed in chapter x., includ- 

 ing species on the ash, hawthorn, alder, and box. 



There are also chapters on collecting and preparing 

 insects, one on insecticides and general remedies, and 

 also a list of trees with injurious insects. 



The subject of beneficial insects is very cursorily 

 dealt with, only four pages being devoted to this 

 interesting part of economic entomology, but the 

 author tells us that " the field of beneficial beetles 

 in forest entomology is rather an unworked one," 

 and probably the same may be said of the other 

 groups, and hence, wisely, a few pages only are 

 allotted to this subject, which is of more interest than 

 any practical importance. There are two points we 

 are very disappointed with in this work, and these 

 are that the author, with all his wide, practical know- 

 ledge, has not told us, firstly, more of his own ideas, 

 and, secondly, more of how we can prevent and de- 

 stroy these interesting forest insects, which levy such 

 a heavy toll amongst our forests, woods, and planta- 

 tions. 



Had this been done, the work, coming as it does 

 from such an authority on forest insects and their 

 ways, would have been of much greater value. 



Fred. V. Theobald. 



OUR BOOK SHELF. 



An Introduction to the Theory of Groups of Finite 

 Order. By H. Hilton. Pp. xii + 236. (Oxford: 

 Clarendon Press, 1908.) Price 14s. net. 

 In many ways this book will prove a useful com- 

 panion to treatises already available ; especially, 

 perhaps, on account of the large number of examples 

 which it contains, and the hints for their solution. It 

 may be confidently asserted that no example in group- 

 theory is too elementary to be useful ; the subject is 

 on one side so very abstract, while on the other the 

 individual properties of groups are numerous, and the 

 protean disguises of the same group are amazingly 

 varied. 



The scope of Mr. Hilton's treatise may be indicated 

 by stating that there is a chapter on Sylow's theorem, 

 one on composition-series, and one on the character- 

 istics of an Abelian group. All the main properties of 

 Abelian groups appear to be mentioned; other groups 

 that receive attention are those of the regular solids, 

 and those known as Hamiltonian, linear homogeneous, 

 and quaternion groups. 



The chapter on characteristics is the last one, and 

 does not profess to be more than a preliminary out- 

 line; it marks very well the limits of the author's 

 plan, and will serve to induce the student to proceed 

 to the very remarkable papers on this part of the sub- 

 ject by Frobenius, Burnside, and others. It is a pity 

 that Mr. Hilton has not given a reference to these 

 and some other of the most important memoirs ; of 

 course, no elaborate bibliography is expected in a work 



1 "Eine moncgr.aph!sche Studie iiber die Chermiden." By Dr. Carl 

 Burner. (Berlin, 190S. ) 



