ON COLLECTING, PREPARATION,. AND MOUNTING. 383 



and prepare it for mounting, under side upwards, as in the previous 

 method. By this method we get a better slide for recognising special 

 structural points. 



If a specimen of a gall insect l)e required for general entomological 

 cabinet purposes, the following method of mounting may be adopted : 

 In addition to preparing the insect as in the first method, get a piece 

 of clean white cardboard, punch a hole in it with a | in. or | in. punch, 

 then attach with seccotine a piece of thinner cardboard to the punched 

 portion, and lay the amalgamated cardboard aside to get thoroughly 

 dry. Thus we have a circular cell of cardboard ; in this place the 

 previously prepared insects, and according to space fix them neatly in 

 the prepared cell with a very tiny drop of seccotine. Lay the insects 

 aside for a time, see that they are kept free from dust, and then finally 

 seal them over with a microscopical cover-glass, a shade larger than the 

 cell. The latter should be done with considerable care, and either of 

 two fixing mediums may be used— viz., Kay's Coaguline, or "brown 

 cement." In either case place a series of tiny drops around the edge of 

 the cell, but not quite touching one another; then let a cover-glass, 

 well cleaned and warmed over a spirit-lamp, fall on the edges of the 

 previously laid drops, again lay it aside until partially dry, and then 

 warm a glass microscopical slip over a spirit-lamp and press gently on 

 the cover-glass, and finally run a ring of the medium round the edge 

 of the cover-glass, and the whole is completed. This method of prep- 

 aration makes an excellent opaque microscopical slide for revealing 

 the natural' colours of the insect. 



The small Cecidomyidee may also be made to " set themselves " for 

 microscopical slides. First stupefy them with chloroform, then pick 

 a single specimen, male or female, place it on a clean cover-glass, 

 place a drop of absolute alcohol on the insect, allow it to evaporate, 

 and then mount in balsam in the usual way. The placing of the 

 alcohol on to the tiny insect is, however, rather difficult. It should, 

 as it were, be allowed to creep under the insect, and so let the delicate 

 wings adhere gently and properly to the cover-glass. If, on the other 

 hand, the alcohol were allowed to drop on to the tiny insect, the 

 wings would double up, and, as a microscopical slide, we should have 

 a complete failure. The alcohol dehydrates the natural moisture 

 in the body of the insect, and as the insects are very delicate, it is 

 well to move them about as little as possible. As the Cecidomyidaj 

 change colour rapidly after death, it is best to examine the unpre- 



