230 



SCIENCE-GOSSIP. 



castaneae ( '= arundinis ) , also the " burnets " the 

 genus Precis and Apoda testudo. Group seven is the 

 Tortricina, the arrangement of species therein 

 being entirely different to any previous formulation, 

 and we properly find among them Cossus. Group 

 eight is the Tineina, led by the clear- wings which 

 are followed by the Gelechias. Group nine are 

 the Micropterygina, which includes the swifts, and 

 the very different looking genera Micropteryx and 

 Eriocephala, at present to be found among the Tineina. 

 The plumes are among Pyralidina. Besides great 

 changes in arrangement, our author introduces 

 many alterations in nomenclature, some of which, 

 especially among the genera, can only be followed 

 by looking up the species included, for few 

 synonyms are given. 



The introduction to this work is evidently the 

 result of much thought, and as an essay upon the 

 Lepidoptera is well worthy of our consideration, 

 though we do not see in it much that has not 

 already been set forth by advanced thinkers and 

 workers in this division of biology. It was, how- 

 ever, only a question of time for such a book as 

 this to be produced, all others hitherto published 

 pertaining too much to the school of "collectors " 

 which became so active about the time when the 

 late Mr. Stainton published his " Manual," and 

 the days of the "Intelligencer." Stainton's- work, 

 from a scientific point of view, was a great advance 

 in its time, but with the organised plan of modern 

 research and correlation of the information gained 

 thereby, the arrangement at present adopted by 

 our lepidopterologists was bound to be revised. 

 For instance, it is only comparatively recently that 

 they have discovered a perfect method of denuding 

 the wings and studying the neuration of the 

 Lepidoptera. Until then it had not received the 

 attention which its importance demands. 



The author will, we feel sure, permit us to quote 

 from his introduction, paragraphs which will show 

 the foundation on which the book before us has 

 been raised. The introduction commences in the 

 orthodox manner of stating of what the Lepidop- 

 tera consist. Then comes the structure of the 

 imago, which is carefully worked out, each part of 

 the animal being separately dealt with in a scien- 

 tific manner, to quote, for instance, "the wings were 

 perhaps originally tracheal gills, respiratory organs, 

 afterwards modified for purposes of locomotion. In 

 form they vary from triangular to almost linear, 

 but the triangular shape may be taken as typical. 

 The junction of the wings with the thorax is the 

 base ; of the two other angles the upper is the apex, 

 the lower the tornus ; of the three sides the upper 

 is the costa, the lower the dorsum, and the outer the 

 termen," and so on. The neuration is carefully 

 described and illustrated by figures of the anterior 

 and posterior wings of a lepidopterous insect, with 

 each of the nerves numbered for reference. In 

 going through the work, it will be found that the 

 various families have the neuration typically 



figured ; as the system of arrangement is largely 

 founded on these features. 



Shortly dealing with the pupa the author treats 

 on the larva and ovum. Then comes variation, 

 on which he remarks: " Probably variability is an 

 original characteristic of all organisms ; but the 

 laws of inheritance, and the favouring of a 

 particular type by natural selection, have tended 

 to produce constancy. This constancy is, however, 

 often imperfectly realised ; that is to say, all insects 

 show more or less variation in some particulars. 

 Thus there is always some variability in size and 

 proportions, often also in colour and markings. 

 Variation in structure is less common ; in certain 

 groups there is variability in some details of 

 neuration. Allied species may be expected to vary 

 in the same way, but otherwise experience is the 

 only guide, the same characters which are 

 absolutely constant in one group being often 

 highly variable in another. Varieties may be 

 broadly classified as being of two kinds, viz., 

 gradual and sudden ; the former being connected 

 with the type form by numerous slight and inter- 

 mediate gradations, the latter not so connected. 

 The former kind represent the outcome of those 

 subjective tendencies to variation which have 

 not been eliminated by the working of natural 

 selection, and may be termed normal ; whilst the 

 latter are apparently due to some objective inter- 

 ference with the process of development, and are 

 in that sense abnormal, the line between these 

 two classes is not always easy to draw in practice, 

 but the distinction is real. Gradual varieties 

 attached to a particular locality or region are 

 called local or geographical forms ; those occurring 

 at a particular time of year seasonal forms. 

 Variation caused by the failure of colouring matter 

 is termed albinism ; that due to an excessive 

 prevalence of black pigment is melanism ; but the 

 application of these terms to varieties which are 

 merely lighter or darker than usual is erroneous. 

 Specimens showing sudden variation in colour or 

 marking are commonly termed aberrations ; in 

 structure, monstrosities. The most common ex- 

 amples of monstrosity are produced by multiplica- 

 tion of parts, as when an insect possesses an 

 additional leg or vein ; or by gynandromorphism, 

 the term used when an individual of one sex 

 exhibits on one lateral half the organic characters 

 of the other sex, more or less completely." 



In dealing with the principles of classification, 

 Mr. Meyrick remarks that: " (1) No new organ can 

 be produced except as a modification of some previ- 

 ously existing structure. (2) A lost organ cannot 

 be regained. (3) A rudimentary organ is rarely re- 

 developed. ... In applying the above-mentioned 

 laws in practice, it must be constantly borne in 

 mind that because two genera are more closely 

 allied together than to any other, it does not follow 

 that either is descended from the other ; it is very 

 frequently the case that both are equally derived 

 from a third genus now no longer existent. . . . 

 In determining the relative value to be assigned to 

 different characters for the purposes of classification, 

 those characters which are adaptive, i.e. liable to 

 be affected by external agencies through the means 

 of natural selection, are generally very untrust- 

 worthy. Conversely, a character which seems of 

 little physiological importance, and not easily 

 modified by ordinary external influences, is com- 

 monly of especial value. Thus colour and outline, 

 the hairs of larvae and the genital organs of imagos, 



