DIPTERA (two-winged FLIEs). 71 



specimens, the ultimate condition of which, when so treated, is rarely 

 as satisfactory as if they had been brought home alive in pill-boxes. 

 If, however, it is necessary for any reason to dispense with pill-boxes, 

 and to use the killing-bottle in the open, a little crumpled tissue- 

 paper should be placed inside it ; this affords a lodgment for the 

 specimens, and so lessens the risk of their being injured by rolling 

 about. It may be noted that Anthracinse when placed in pill-boxes 

 are very apt to inj ure their wings by buzzing about, and large Tabanidce, 

 (EstridcB^ and certain other Diptera are liable to snfter in the 

 same way. On the other hand, the hairy and scaly body-covering 

 of Anthracinse is very easily rubbed off, so that if carried in the 

 killing -bottle they must be treated with special care. It is always 

 advisable when out collecting to carry a killing-bottle for use 

 in case of need, in the event of the supply of pill-boxes running 

 short. Diptera on windows may be captured in pill-boxes ; if the 

 edge of the box be slightly raised from the glass on one side, 

 and a piece of thin card passed under so as to shut the fly in 

 the box, or a little tobacco smoke blown into it so as temporarily 

 to stupefy the fly, it will be found easy to slip on the lid without 

 allowing the insect to escape. 



Spirit not to be Used. 



Unless intended for dissection, Diptera must on no account be 

 placed in spirit. Since all descriptions of Diptera have been based 

 upon dried specimens, flies in spirit have to be taken out, dried, and 

 pinned before they can be examined and compared with descriptions. 

 In drying, however, they invariably shrivel ; while immersion in 

 spirit often causes colour-markings to disappear, and inevitably 

 results in hairs, scales, etc., being washed off or matted. Sj^ecimens 

 intended for dissection (as when it is desired to examine some specially 

 remarkable structure, such as the proboscis or genitalia) should, 

 however, always be placed in a small tube of spirit, with a plug of 

 cotton-wool on the top of them to prevent their being injured by 

 washing about. Before being preserved in spirit (90 per cent, 

 alcohol) specimens should be fixed by being brought to boiling 

 temperature in a test-tube of water, or preferably a mixture of 

 equal parts of 90 par C3nt. ^,lcohol (ordinary rectified spirit) and 



