THE ATTRACTIONS OF ENTOMOLOGY 167 



is sprinkled over a table, on which a pound of plasticene is 

 then rolled out with a rolling pin or bottle, and another 

 i ounce of the napthalene having been sprinkled on the top 

 of this, is well rolled in and kneaded up. This will probably 

 make the plasticene dry and crumbly, in which case it must 

 be moistened with glycerine or liquid paraffin until it regains 

 its former sticky condition, suitable for modelling. 3 This 

 material, which may be called "napthaplas," should be kept 

 m a covered tin, and not be exposed to strong sunlight or 

 other source of heat, as this makes it soft and messy. 



The rings of "napthaplas" are best prepared by putting 

 a small piece, — about the size of a bean, but varying with 

 the size of the insect, — on a flat surface, and covering it with 

 a glass plate, or one of the above slides, which is then rolled 

 backwards and forwards a few times, under gentle pressure, 

 until the "napthaplas" takes the shape of an elongated roll 

 of the required thickness; viz., about once and a half the 

 thickness of the specimen. The two ends of this roll are 

 taken up between the finger and thumb and the loop so 

 formed is cast round the insect as it lies in position on the 

 slide, making a complete circle wide enough to allow for the 

 spreading of the insect's limbs, etc., under the pressure of 

 the upper slide; the superfluous stalk of the loop is then 

 detached, and at this point where the ends meet on the slide, 

 a secure joint is made by a few touches with a blunt stick 

 or pen handle, care being taken to make it the same thickness 

 as the rest of the ring; the specimen is then completed as 

 previously described. With a very little practice the whole 

 process can be neatly carried out in a few minutes, and when 

 complete, the little preparation permits the most fragile 

 insect to be handled with impunity, enables every part of it 

 to be readily examined with the naked eye, lens, or micro - 



3 If the very poisonous substance, cyanide of potassium, be incor- 

 porated with the plasticene in an exactly similar manner to the above, 

 the resulting material, which may be called "cyanoplas," can be spread 

 out in a thick even layer on the bottom of a tin with a tightly fitting 

 lid, so as to form a very effective killing receptacle for freshly caught 

 insects. The layer of "cyanoplas" can with advantage be covered 

 over with a sheet of perforated tin so as to prevent the insects adhering 

 to its sticky surface, and a further improvement consists in dividing 

 the interior into four compartments by means of two thin plates at 

 right angles to each other, so that, say, moths, beetles, flies and spiders 

 may be kept separate from each other. This forms a very convenient 

 killing and collecting box combined, and inside it insects remain 

 perfectly fresh and supple for an indefinite period pending mounting. 

 A few little glass tubes, each fitted with a plug of "cyanoplas" 

 (wrapped in muslin to facilitate removal) are very useful for tiny, 

 delicate specimens which would be lost or damaged in the large tin. 



