COLLECTING DIPTERAHYMENOPTERA. 287 



gives full directions, in which the chief points are that they 

 must not be pinned in the middle dorsal line of the thorax; 

 and that they should not be killed with alcohol, while killing 

 with potassic cyanide is not recommended. 



Very small Diptera should not be killed when they can- 

 not be immediately pinned; too much material should not 

 be collected in the net at one time; and hairy flies should 

 not be taken in the hand to pin, but handled with fine for- 

 ceps, while lacquered-iron needles or lacquered-iron wire 

 should be used for pinning instead of common insect-pins 

 or silver wire (which contain copper and are therefore 

 liable to corrode) ; wire should be used for all flies under 

 3 mm. in length. (Abstract in Psyche, iii. 226.)* 



Aquaria are necessary for the maintenance of aquatic 

 larvge. If quantities of swamp-mud and moss with decaying 

 matter are kept in boxes and jars, multitudes of small flies 

 will be hatched out. Leaf-mining and seed-inhabiting 

 species can be treated as Micro-lepidoptera, and earth-in- 

 habiting larva? like ordinary caterpillars. Dung, mould in 

 hollow trees, stems of plants and toadstools, contain numer- 

 ous larvae or maggots, which must be kept in damp boxes. 



COLLECTION AND PRESERVATION OF HYMENOPTERA. 



These insects are exceedingly abundant, and especial at- 

 tention should be paid to collecting the smaller species. 

 They should be pinned through the thorax, high up on the 

 pin, and those that are not hairy collected in alcohol. In 

 fact, as much depends on the study of the softer parts of 

 the mouth-appendages, specimens of each species so far as 



* Dr. Williston tells me that " Prof. Mik advises ordinary sulphur- 

 matches to kill specimens, and the process has some merits, though I 

 think it is inferior to a lined cyanide bottle. He uses an oval tin box, 

 in which there is left an opening between the opposing edges that will 

 admit a match. The fly is put in the box, the match struck and in- 

 serted till the sulphur is consumed, then withdrawn and the cover 

 fully closed till the fly is dead." 



