2CXf 



SCIEXCE-GOSSIP. 



PRESERVATION OF COLOURS OF DRAGONFLIES. 

 Bv W. H. Ndnney. 



T^ROM the time when first dragonflies came to 

 be collected there has been almost unceasing 

 outcry against the extremely fleeting nature of 

 their colours during preservation, and various have 

 been the devices by which it has been attempted to 

 provide a remedy, with, however, but little success. 

 Although in certain species the brilliant colours 

 may be retained for perhaps a few days after the 

 death of the insect, the majority, so distinct in their 

 colouration whilst in life, eventually by its total 

 loss, become reduced to one dead and monotonous 

 level. No sadder thing occurs in natural history, 

 and in order to obviate this, I, some two or three 

 years ago, entered upon a series of experiments 

 which have extended almost to the present time. 

 Although the results have by no means been 

 entirely successful, they have been sufficiently 

 so to warrant the hope that in time we may be 

 able to retain in our cabinet-specimens the colours 

 in their pristine beauty. 



The older methods of preservation are in general 

 well known, but may perhaps be reiterated here, 

 inasmuch as they necessarily formed the starting 

 point for my own experiments. The method most 

 in vogue for the larger species of dragonflies is to 

 carefully remove the contents of the body by way 

 of a slit down the entire length of its underside, 

 and to afterwards insert a roll of cotton wool or 

 paper, both to act as a support, and to bring into 

 relief what little of the insect's colour may remain 

 after the operation. Some collectors remove the 

 pigment altogether (delightfully Yandalic idea) 

 replacing it by means of a coloured powder loosely 

 shaken into the body cavity, by a coloured paper 

 roll, or, what is better, by painting the required 

 tones directly on the epiderm itself. These methods, 

 however, are but of colour substitution, not preser- 

 vation ; I therefore pass on. 



With the introduction of the method invented 

 by Professor Steffanelli, described in the Bulletin 

 of the Italian Entomological Society, a new era 

 may be said to have commenced. His method is 

 that of desiccation of the insect under the receiver 

 of an air-pump, the exhausted air being replaced 

 by the fumes of sulphuric ether, well known for its 

 desiccating and preservative properties. The re- 

 sults are in general nearly all that ean be desired. 

 An air-pump is, however, not at everyone's com- 

 mand, and the colour-preservation of the insects 

 is thus rendered unnecessarilv complicated and 

 expensive. Sulphuric ether alone, injected into the 

 bodies of dragon-flies, will frequently preserve the 

 colours. 



My own method is the direct antithesis of that of 



Professor Steffanelli. Instead of desiccating the 

 insects, I endeavour to keep them in a constant 

 condition of moistness. For this purpose I have 

 tried many chemical substances, amongst others 

 chloride of calcium and glycerine alone, or com- 

 bined in varying proportions, and a preparation 

 known commercially as Professor Barfi's boro- 

 glyceride. In the use of the calcium chloride I 

 have been fairly successful ; it has, however, a 

 tendency to discharge instead of preserve certain 

 colours. With the boro-glyceride I have been 

 successful almost to the elimination of failures, 

 some of the results being extremely fine. 



After making the usual longitudinal slit in the 

 under side of the creature's body, I withdraw so 

 far as possible the contents, and afterwards fill the 

 cavity with the boro-glyceride of the ordinary com- 

 mercial strength, without allowing the chemical 

 to in any way soil the outside of the bod} 7 . The 

 result is, that winist the colours are preserved, the 

 body never entirely dries, and consequently cannot 

 be broken off by any shock given to the cabinet, 

 drawer or store-box, this last being another great 

 advantage of the use of a slightly deliquescent 

 antiseptic. 



In the case of the smaller Agrionidse, I inject the 

 boro-glyceride, slightly weakened by the addition 

 of water, with a very fine hypodermic syringe into 

 the bod}- extremity, and, if necessary, run in the 

 usual bristle for strengthening purposes. 



In concluding, I may mention that the colours of 

 the body of znJEschna cyanea, treated by my method 

 somewhat over two years ago, are at the present 

 time as bright as when the creature was alive. 



I have also applied this method of colour pre- 

 servation to the delicately coloured Ephemerida 7 :, 

 or day-flies, with, in some instances, better results 

 than with the dragonflies, this probably being 

 due to the usual freedom of the abdominal cavity 

 from elements of corruption. 



The method is, of course, equally applicable to 

 the preservation of such soft-bodied creatures as 

 lepidopterous larvae and spiders, being, however, 

 more useful for the latter. 



Upon receiving two specimens of a species, to- 

 gether with stamps necessary for transmission, I 

 shall be pleased to return one of them, treated by 

 my method, in the order of arrival. The dragonfly 

 season being now past, quite fresh specimens are, 

 of course, oat of the question. Those sent should, 

 however, be as nearly fresh as possible, in order to 

 obtain good results. 



25, Tavistock Place, Bloomsbury, W.C.; 

 September yth, 1895. 



