164 



while in the case of species that I have reared the notes furnish data 

 upon the habitat. This makes unnecessary preliminary details on 

 these points. In fact the Diptera have such a variety of habits in the 

 larval and imaginal stages, and are so generally distributed, that one 

 might be pardoned if he were to dismiss the subject with the laconic 

 remark, "omnivorous and omnipresent". 



METHODS OF COLLECTION AND PRESERVATION 



It is necessary, in my opinion, in papers of this nature to give 

 some general directions regarding methods of collecting and, as a 

 part of collecting, rearing species. 



For the ordinary collecting of forms that frequent manure, de- 

 caying wood, fungi, and mud or comparatively ^ry earth, as well as 

 phytophagous species, the best temporary receptacle is a small round 

 tin box about an inch and a half in diameter and three fourths of an 

 inch deep. Dealers in entomological supplies have these for sale, and 

 they may be obtained with a paper-covered lid, upon the surface of 

 which necessary data may be written. Many species may be reared 

 to maturity in these boxes, the principal objection to this course being 

 that it is not possible to learn whether the flies have emerged without 

 opening the box, and frequently the specimen escapes upon the remov- 

 al of the lid. 



I have had very satisfactory results with rearing-cages consist- 

 ing of Petri dishes, the upper dish fitting over the lower when inverted. 

 These cages, especially in the spring, proved all that were required to 

 produce imagines from the larvae of Empididae. Xylophagidae, 

 Syrphidae, and many other families. 



Aquatic species may be put in Mason fruit-jars or in small 

 bottles, a convenient size of the latter being two-ounce. If not too 

 tightly corked, specimens may be kept in such receptacles over night, 

 but I find it best to use a cotton stopper instead of a cork unless while 

 carrying the material in from the field. Many species, in fact most 

 of the smaller forms, may be successfully reared in the two-ounce 

 bottles, but I prefer to remove them during the pupal stage, or just 

 before they transform to that stage, to a two-dram vial containing a 

 little water and fitted with a cotton stopper. If transferred before 

 transforming to the pupa the larval skin may be more easily found 

 than in the larger bottle. 



A mistake frequently made by entomologists in preserving larvae 

 is to put the live specimens into 85% alcohol. This course almost in- 

 variably results in a shrinking of the skin and consequently seriously 



