154 ENTOMOLOGICAL NEWS [May, '22 



are given illustrating the metamorphosis of eacli of the Orders of 

 Insects that come under these two headings. This leads, in Chapter V, 

 to the consideration of wingless insects and the effect of parasitism on 

 the form of an insect, and this secondary winglessness is then con- 

 trasted with the primitive unaltered winglessness of the true Aptery- 

 gota, the Spring-tails and Bristle-tails. The ground thus covered enable* 

 the author to give in Chapter VI a concise classification of the Insecta, 

 in which twenty-three Orders are recognized. Chapter VII deals with 

 the correlation between the growing insect and its surroundings, and 

 we are here introduced to the secondarily aquatic larvae of certain 

 Diptera (sandfly, mosquito, etc.), the habits of burrowing and sucking 

 the juices of plants, the formation of galls, the parasitism of one insect 

 by another, and finally the care of the helpless young by the adult, as 

 in the case of ants. The last chapter deals with the general -problems 

 of insect transformation, and emphasizes the apparent paradox that, 

 whereas, in other groups of animals, low-grade forms are found to 

 undergo more profound changes than high-grade forms, yet in the case 

 of insects the reverse is true, metamorphosis becoming more and more 

 complete as we pass upwards to the more highly evolved forms. The 

 reason for this is very clearly explained, and we can recommend th.b 

 part (Chapter VIII) as the best in the book, particularly the illuminat- 

 ing discussion as to the probable primitive type of insect larva, the 

 evolution of the two types of wing-growth, and the short but excellent 

 summary of the palaeontological evidence. 



Any book dealing with so large a subject can scarcely claim to be 

 original, but the author certainly has as much claim as anyone to be con- 

 sidered an authority on his subject. Thus we note, as we should expect, 

 that he has introduced illustrations and examples from a number of 

 recent researches by modern authors, which greatly enhance the value 

 of the book. While the general conception and detail of the book are 

 alike excellent for the beginner, the more advanced student will note 

 some omissions of considerable importance. For example, in dealing 

 with the problem of wing-growth, no mention is made of the turning 

 o\er of the wing-buds in Odonata and certain Orthoptera, in which the 

 hindwing sheath conies to overlie that of the forewing. In dealing with 

 the evolution of the pupal state (Chapter II) the author passes in 

 review the various larval forms found in the Hymenoptera, but quite 

 fails to mention the praepupal or subpupal stage, which is the most 

 significant of all facts in connection with this problem, and so misses 

 the clue to the explanation of the reduction of the number of instars, 

 without which a true view of the meaning of the pupal state can 

 scarcely be attained. Again, much has been written in late years on 

 the internal changes accompanying metamorphosis, yet this fascinating 

 and intricate subject is dismissed in ten pages at the end of Chapter IV. 

 There are many students of insects at the present day who would be 



