HARDWICKE'S SCIENCE-GOSSIP. 



179 



■confinement is obvious, and the consequent impossi- 

 bility of keeping them invariably exposed to the 

 weather under natural conditions must be equally clear. 

 There is, however, no practical reason why, where the 

 name and life-history of a species is perfectly known 

 to the breeder, the pupa; should not be exposed under 

 natural conditions* until within a few days of the date 

 when the perfect insects may be expected to emerge ; 

 and I am of opinion that this method might with ad- 

 vantage be adopted to a much greater extent than it is 

 at present. 



It may be argued against this suggestion that 

 some species are very erratic as to time in the 

 emergence of the imago, but in such cases a sufficient 

 margin of time should of course be left to render the 

 loss of specimens by this means impossible. 



The real difficulty we have to contend with is to 

 find a place where the boxes will remain undisturbed, 

 and not be subjected to the occasional predatory visits 

 of centipedes and other dangerous intruders. 



Even when the collector is prejudiced against com- 

 ■pletely exposing his pupre to the weather, under the 

 conditions before mentioned, the process may be 

 modified to a considerable extent, and yet be used with 

 advantage — such for instance as keeping the pupce 

 cages always in the open air. 



It is a common thing for lepidopterists to keep 

 their pupae inside the house, and often in a room the 

 temperature of which is usually several degrees 

 higher than the outside air. This is a mistake which 

 should be studiously avoided, as to it may be referred 

 the loss to young collectors of many valuable speci- 

 mens, to say nothing of the disappointment oc- 

 casioned by their want of success. We need not 

 go far for an explanation. The heated air of the 

 room dries the pupre to a much greater extent 

 than is natural, and the inevitable result is that 

 the pupee case becomes unusually hard, and often 

 unbreakable to the imago, which either does not 

 make its appearance at all, or ultimately emerges 

 deplorably crippled, as the result of ignorant and 

 inconsiderate manipulation. 



Dr. H. G. Knaggs, F.L.S., in his "Lepidopterists' 

 Guide," p. 69, says, "I have long been satisfied that 

 <lamping is as a rule a great mistake," but I hardly 

 think the reasons t given by Dr. Knaggs sufficient 

 to support such an opinion. Although there are 

 numerous entomologists who endorse Dr. Knaggs' 

 remarks, I think by far the greater number are in 

 favour of damping, and I may safely say that the 

 process is coming almost universally into use. 



Some pupK of course require much more moisture 

 than others ; take for instance the pupae of Calli/iior- 



* Exposed to the rain, &c., in shallow open boxes, the cocoons 

 being undisturbed as far as possible, and care being taken 

 to have the bottom of the boxes abundantly perforated for the 

 outlet of moisture, the accumulation of which would probably 

 be fatal.— W. J. V. V. 



t As I presume almost every lepidoptenst possesses a copy 

 of the invaluable " Guide," it is unnecessary to quote thera 

 here.— W. J. V. V. 



p/ta Jacohatv, which, under natural conditions, pass 

 the winter underground, generally in very moist and 

 swampy places. 



I have found the larvcc of this pretty insect in 

 places where its pupas must occasionally, during the 

 winter months, become actually submerged in water j 

 and the absurdity of keeping such pupae in a dry 

 place, without ever introducing any moisture into 

 their cage, appears to me to be abundantly apparent. 



A large proportion of lepidopterous insects pass 

 the winter underground, in the pupae state, and it is 

 therefore evident that they must be influenced by rain, 

 snow, &c., to a very considerable extent. Too much 

 moisture should of course be avoided, as it is likely 

 to produce "mould " and thus destroy our specimens ; 

 but any person would be able to regulate the supply 

 sufficiently to avoid this undesirable result. During 

 frosty weather, damping should of course be discon- 

 tinued, as it would not be at all surprising if a col- 

 lector who damped his cages during a frost, ultimately 

 formed an opinion adverse to the process. 



The plan generally adopted by lepidopterists, 

 with insects that pass the winter in the pupae state, is 

 to keep them among layers of moss, &c., in a breeding- 

 cage, or box, which is usually placed in an outhouse 

 where it will be exposed to the natural changes of 

 temperature and most other meteorological conditions, 

 except rain and snow. 



Towards the end of winter, when the weather 

 begins to become warmer, and the amount of evapo- 

 ration consequently greater, it is advisable to slightly 

 damp the pupae, which can easily be accomplished 

 by sprinkling a little water on the surface of the 

 moss, &c., with the aid of a house-painter's brush. 

 (71? be continued.) 



NOTES ON SOME COMMON SEA-SLUGS. 

 By Dr. p. Quin Keegan. 



THE great group of animals popularly called shell- 

 fish (MoUusca), is one of the most interesting 

 and most familiarly known departments of the king- 

 dom of Nature. To the eye of childhood nothing is 

 more fascinating than the beauteous and ever-varied 

 shells which lie storm-cast in countless thousands on 

 our sea shores ; while to the man of science few 

 researches are more instructive and impressive than 

 that into the structure, habits, and economy of the 

 flabby animals who have fabricated these shelly 

 homes. Stored up in the cabinet, their aspect imme- 

 diately carries away the thoughts to the sea, its 

 many-murmuring voice, its keen freshness of air, its 

 infinite tints and hues of colour and transformations 

 of form. The Mollusca are found in the greatest 

 numbers within the realms of the ocean. From the 

 upmost high -water mark down to abysmal depths thej'' 

 abound in lavish profusion. Sometimes they lie 

 buried deep in the sea-slime, sometimes they cling to 



