90 THE ENTOMOLOGIST. 



perforated zinc, with a layer of plaster of Paris at the bottom, and 

 covered at the top, if necessary, with a sheet of glass. It is intended 

 to be used in aquaria, and particularly for eggs or very young nymphs. 

 These are to be placed in the cylinder, while the food supply is outside 

 in the body of the aquarium, and, the perforations being small, animals 

 likely to prey on the little nymphs are not able to get in. 



Not every one will agree with Dr. Needham when he says that to 

 get good specimens of the largest dragonflies it is easiest to breed 

 them. They will not feed in captivity, and therefore die before their 

 colours are matured. 



Besides the points called attention to above, this interesting paper 

 contains many other hints on collecting, breeding, and preserving 

 Neuroptera with aquatic nymphs. — W. J. Lucas ; Kingston-on-Thames, 

 February 10th, 1900. 



The use of "Formalin" as a Preservative of Insects. — Now that 

 this liquid is coming so much to the front as a universal antiseptic, it 

 behoves entomologists to ascertain how far they can apply it to their 

 own ends with advantage. There appears to be some doubt as to its 

 suitability for preserving museum specimens in place of spirit (see 

 'Nature,' 61, 204), and, on account of the rigidity imparted to the 

 insects, formalin would be an obviously unsuitable medium in which 

 to collect Coleoptera, or for killing purposes either. On referring to 

 past volumes of the ' Entomologist,' I find that formalin has been 

 used with success to retain the natural form and colour of larvae and 

 pupje after death (xxxii. 132, 188), but no account is given of 

 employment as a preservative for the collection, although suggested 

 by Mr. Blandford (xxx. 21). Having myself had some acquaintance 

 with the remarkable germicidal property of formalin, which is stated 

 by some of the best authorities to be second only to sublimate, I have 

 used it to destroy mould among my insects, with results which are to 

 me quite satisfactory. Every entomologist living in a damp locality 

 will know how easily boxes of insects become infested with this plague, 

 and when once established how difficult to eradicate. Painting with 

 sublimate solution is sure but troublesome, and does not add to the 

 beauty of the specimens ; carbolic acid also must be applied directly to 

 the insect. As far as my experience goes, formaldehyde (of which 

 formalin is a forty per cent, solution in water) is the only substance 

 completely efficacious as a vapour. The method I employ is to render 

 the infested box or drawer as nearly as possible air-tiyht, and to enclose 

 in it a piece of cotton-wool on which are poured from six to twelve 

 drops of formalin according to size. This is then set on one side for a 

 week, when the spores should all be killed. If any mouldy insect is 

 then examined, it will be seen that the mycelium has shrivelled up, 

 and, in the case of Coleoptera, may be removed with a brush. As it 

 is generally more satisfactory to destroy at once Lepidoptera which are 

 attacked to any extent, it is rather as a preventive than a cure that 

 I would suggest its use to collectors of this order. By treating all 

 drawers and boxes two or three times a year in the way recommended, 

 and submittmg all fresh specimens to a dose, one may, I think, be 

 reasonably sure of not seeing mould or mites either, though ordinary 

 care is sufficient to prevent the appearance of the latter. A natural 



