﻿NOTES AND OBSKRVATIONS. 41 



New Work on British Butterflies.— It is no doubt some- 

 what of an open secret that for some thirty years or more Mr. F. W. 

 Frohawk has been collecting first-hand material for a complete 

 history of the British Butterflies. In all some 1400 coloured 

 drawings, delineating the various stages of each species from ova to 

 imago, have been prepared in Mr. Frohawk's best style, together 

 with copious explanatory manuscript. The whole was in order for 

 the printer, and arrangements for publication were being made when 

 the unfortunate outbreak of war rendered it impossible to proceed, 

 and the publication of the complete work will, therefore, have to 

 stand over until things have settled down again, when it is hoped 

 that it may be produced in a style worthy of the labour that has 

 been spent upon it. As, however, there is no guarantee when this 

 opportunity may occur, it has been thought desiral)le that the whole 

 of the vast information contained in the work should not be longer 

 withheld from present-day entomologists. Arrangements have, 

 therefore, been made with the proprietors of the ' Field ' to publish 

 it in an abridged form, and the first instalment appeared in the issue of 

 that journal for December 26th last, and has since been continued 

 weekly. In all some five hundred black-and-white reproductions of. 

 the more important of the original drawings, from photographs by 

 Mr. A. W. Dennis, will appear, together with an abridged account 

 of each species. The parts already published cover the introductory 

 remarks and descriptions of the species of the PieridiE, and are in all 

 respects satisfactory. The present issue, although admittedly but an 

 instalment of what it is hoped may follow later on, when it is possible 

 to pubHsh the complete work, bids fair to be a valuable addition to 

 our knowledge of this interesting group of the British Lepidoptera, 

 and as such we heartily commend it to our readers. — E. A. 



Use op Formalin in Setting Insects. — In reference to the 

 notes on this process which have been published recently in the 

 ' Entomologist ' (xlvii. p. 325, and xlviii. p. 19), it may be of interest 

 to offer some explanation of the action of formaldehyde on insect 

 tissues. In the first place, formaldehyde is only known in solution, 

 usually of about forty per cent, strength, and this is the " formalin " 

 of commerce. " Formalin " liberates formaldehyde as vapour on 

 evaporation, or more rapidly by boiling. Formaldehyde has the 

 property of uniting chemically with gelatin and albumen ; also with 

 the animal tissues from which these are derived. It also, apparently, 

 unites with chitin, the skeletal tissue of insects. The effect of this 

 union of formaldehyde with any animal tissue or product is to 

 render the latter insoluble in and resistant to the action of water ; it 

 is this property which no doubt explains the fixation of " set " 

 insects, since after treatment with formaldehyde vapour these do 

 not soften under the influence of moisture. With regard to the 

 suggestion of Messrs. St. John and Kershaw, that this might be used 

 also to prevent " grease," so far as I know formaldehyde does not 

 combine with fats, but it is possible that it might prevent the decom- 

 position which produces these undesirable greasy substances in the 

 insects' bodies. In this connection I might again draw entomolo- 

 gists' attention to the use of formalin as a preventive of mould 



ENTOM. — FEBRUARY, 1915. ' E 



