28 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



event some of the larvae within might escape, or others from outside 

 gain entrance to the bag. 



For Sarcophagidae and some other Diptera, Lopes (<5^) has used a 

 nutritive medium, common in bacteriological technique, consisting of 

 10 parts of nutritive agar to 1 part of normal horse serum. This me- 

 dium may be kept in 50-ml. ampules, dated, and thus preserved for 

 months. The puparia will be formed on the surface of the medium 

 or the walls of the tube. 



Special directions for rearing many other flies, including Tipulidae, 

 Phoridae, Psychoda, Tnbifera (Eristalis) and other Syrphidae, Pol- 

 lenia, Stomoxys, Musca, Muscina, Piophila, and Drosophila, are given 

 by Galtsoff and coworkers (44)- 



PRESERVATION AND MOUNTING 



Larvae may be killed by dropping them into water near the boiling 

 point and allowing it to cool. Some larvae may be mounted dry, but 

 the technique is not simple ; they should never be pinned in the same 

 fashion as an adult. The simplest way of preserving insect larvae is 

 to put them in TO- to 80-percent alcohol. For dipterous larvae alcohol 

 alone is sufficient ; if, however, glycerol is added at the rate of about 1 

 part to 25 parts of 80-percent alcohol, it will keep the larva moist 

 should the alcohol evaporate. Glycerol is objectionable for use with 

 larvae of some other orders, in which the hair pattern is of great value 

 in identification. 



The best way to preserve adults is to mount them while fresh on 

 insect pins. Only standard, noncorrosive pins should be used ; in nor- 

 mal times these may be purchased from any dealer in entomological 

 supplies. In pinning flies, the pin should be inserted through the 

 right side of the thorax, at a sufficient distance from the edge of the 

 body so that the sides of the thorax will not break, yet not so far to 

 the left that the bristle pattern of that side is disturbed (fig. 7, C). 

 About one-fourth the length of the pin. or enough to enable one to 

 handle the specimen without touching it with the fingers, should 

 extend above the insect. The size of the pin should depend on the size 

 of the specimen. It is dismaying to see a small fly speared with a 

 heavy pin and the thorax ruined; it is likewise annoying to find a 

 heavy-bodied fly on a 00 pin. For general purposes, number 2 or 3 

 pins are best. 



There are several ways of mounting small flies, and each method has 

 its adherents. The one most commonly favored is to cut a small 

 triangle of light white cardboard, insert the pin through the base, and 

 attach the insect to the apex (fig. 7, B) . A large triangle is unsightly ; 

 a desirable size is about 1.5 mm. at the base by 7-8 mm. long. Tri- 

 angles may be purchased from supply houses, or, if they are needed in 

 qualities, punches are available. Balsam or shellac is satisfactory for 

 attaching the insect to the point of the triangle, although some prefer 

 a more quickly drying adhesive. In mounting on triangles, one should 

 take care to limit the adhesive to structures on one side of the insect, so 

 as to leave the whole of one side intact and undamaged. 



If proper mounting equipment is not available, the flies may be 

 preserved in pill boxes between layers of Cellucotton, soft tissue paper, 

 lens paper, or a similar material. Tin boxes should not be used, espe- 

 cially in warm, wet climates, where mold and mildew are factors in 



