. DIPTERA. 



toadstools contain numerous larvae or maggots, as the young 

 of flies are called, which must be kept in damp boxes. 



Flies can be pinned alive, without killing them ~by pressure, 

 which destroys their form ; and numbers may be killed at once 

 by moistening the bottom of the collecting box with creosote, 

 benzine or ether, or putting them into a bottle with a wide 

 mouth, containing cyanide of potassium. Minute species can 

 be pinned with very slender pins, or pieces of fine silver wire, 

 and stuck into pieces of pith, which can be placed high up 

 on a large pin. In pinning long-legged, slender species, it is 

 advisable to run a piece of card or paper up under their bodies 

 upon which their legs may rest, and thus prevent their loss 

 by breakage. Of these insects, as with all others, duplicates 

 in all stages of growth should be preserved in alcohol, while 

 the minute species dry up unless put in spirits. 



In the genuine flies the thorax is highly centralized ; the 

 maxilla} are covered by the labrurn, and the lab him is not pro- 

 vided with palpi. The females lay eggs from which the larva' 

 are hatched. They are also divided into the Nemocera, com- 

 prising those flies having long, thread-like, many-jointed an- 

 tennae, and embracing the higher families, i.e. the C-nUcidw, 

 Tip u 1 i d w , Bibion i d ce and E h yp li i d vc ; while the remain- 

 ing families of this division are included in the Brachyceru. or 

 flies with short antenna, such as the Muscidce, etc. But the 

 fossil genera, Electra and Chryothemis, discovered b t y Profes- 

 sor Loew in the amber of the Tertiary formation, and a North 

 American genus of Xylophagidw , and the genus Rachieerus, 

 have intermediate characters combining these distinctions, 

 which are thus shown to be somewhat arbitrary. 



Latreille. The family of Mosquitoes or Gnats 

 have the mouth-parts very long and slender ; the maxilla? and 

 mandibles are free and lancet-like. Figure 274 (A, larva ; c, 

 its respiratory tube ; B, pupa ; c?, the respiratory tubes ; o, the 

 end of the abdomen, with the two oar-like swimming leaves, 

 seen in profile at B, from drawings made by Mr. E. Burgess,) 

 illustrates the transformations of a species inhabiting brackish 

 water in the vicinity of Boston. The larva 1 remain most of 

 the time at the bottom feeding upon decaying matter, thus act- 



