[83] 



COLLECTING AND PRESERVING INSECTS RILEY. 



existence, the heat must not be slight, but a little practice shows the proper tem- 

 perature required. If the heat be insufficient, a drying up instead of a natural dis- 

 tention ensues. The insect to be roasted is to be pierced by a piece of silver wire 

 on the under side of the thorax, but it is not to be inserted so far as to damage 

 the upper side, and the wire should then be carried through a disk of pith, placed 

 beneath the insect, on which the legs should be set out in the desired position. 

 But with some objects, such, for instance, as a young Strachla, the drying pro- 

 ceeds very quickly, so that if distention be not observed then the heat is too great, 

 for the expansion of the air inside will force off the head with a loud report ; also, 

 with softer, thicker Pentatoniidse care must be taken to begin with a heat only so 

 strong that the internal juices do not boil, for in such case the preparation would be 

 spoiled. It is of advantage to remove the cylinder from time to time, and test, by 

 means of a lens, if a contraction of the skin has taken place on any part ; if so, the 

 roasting is to be continued. The desired hardness may be tested with a bristle or 

 wire. 



For Aphides the living Aphis is to be put on a piece of white paper, and at the mo- 

 ment when it is in the desired position it is to be held over the flame, and in an in- 

 stant it will be dead and will retain the attitude. Then put it, still on the paper, 

 into the oven ; or, still better, hold it over the heated tin. carefully watching the 

 drying and rnaving the paper about in order to prevent it getting singed. The roast- 

 ing is quickly accomplished in either way, but somewhat slower out of the oven es- 

 pecially in the larger kinds, such as Lachnus. If the paper turn brown it is a sure 

 sign that caution is requisite. To pierce these brittle preparations for preservation 

 is hazardous, and it is a better way to mount them with gum on card, placing 

 some examples on their back. 



For Cecidomyida?,Agromyzidse,Cynipida?, and other small insectsliable to shrink, yet 

 containing but little moisture, such as Podurida?, Pediculida3, Psyllidse, etc., another 

 method is adopted. Over the insect, mounted on a wire, etc., as above directed, a 

 thin chemical reagent glass or glass rod, heated strongly at one end, is held, and the 

 heat involved is generally sufficient to bring about the immediate drying and dis- 

 tention, but if the heat be too little the process must be repeated; and, although by 

 this method the danger of burning is not obviated, yet the position of the legs is 

 maintained much better than by the aforesaid roasting. 



Larva; of all kinds, up to the size of that of Astyiwmus cedilis, even when they have 

 long been kept in spirits, may be treated successfully by the roasting method ; but 

 with these objects care must be taken that the heat is not too strong or else the 

 form will be distorted. For small larva? it is preferable to use a short glass, in order 

 better to erTect their removal without touching the upper part, which becomes covered 

 with steam, and contact with which would cause the destruction of the preparation. 

 Larva? of Coleoptera, which contain much moisture or have a mucous surface, must 

 lie on a bed of paper or pith in order to prevent adhesion and burning, and these 

 may be further avoided if the cylinder be slightly shaken during the process, and the 

 position of the object be thereby changed. 



Many Aphides aiid Coccids are covered with a waxy secretion which 

 interferes very materially with their easy examination. Mr. Howard 

 has overcome this difficulty by the following- treatment : 



"With Aphides and Coccids which are covered with an abundant 

 waxy secretion which can not be readily brushed away, we have adopte< 1 

 the plan of melting the wax." We place the iusect on a bit of platinum 

 foil and pass it once over the flame of the alcohol lamp. The wax melts 

 at a surprisingly low temperature and leaves the insect perfectly clean 

 f< >r study. This method is particularly of use in the removal of the waxy 

 cocoon of the pupse of male Coccidie, and is quicker and more thorough 



