PRESERVING OVA, LAEVM AND PUP^E 131 



injector of small size the contents of the eggs can be removed ; and 

 then, by the same instrument, a warm solution of gelatine, coloured 

 in such a way as to restore the natural tint, may be forced into the 

 empty shell. As the gelatine cools and hardens, it prevents any 

 shrinking of the shell, and thus both form and colour are well 

 preserved. 



For the preservation of larvse you will require one or two 

 simple appliances. 



The first of these is a suitable glass blowpipe, one form of which 

 is here illustrated. It consists of a glass tube, one end of which 

 has been drawn out very fine ; a piece of watch spring tied to it in 

 such a manner that it will hold the skin of a larva at the small end, 

 and a piece of india-rubber tubing at the other end, pressed by 

 means of a brass spring clip. 



A little drying oven is also very useful, but not absolutely neces- 

 sary. If you decide to have one, any square box of sheet iron (not 



FIG. 64. A BLOWPIPE FOR LARVAE. 



soldered tinned iron) may be readily converted into one. It must 

 be provided with a hinged door in the front with a ventilator at the 

 bottom, a hole for the escape of hot air at the top, and a tripod^vire 

 stand inside on which to rest the specimens while drying. The 

 whole should be supported on a wire stand, so that heat may be 

 applied below. 



Each larva to be preserved should be dealt with in this way. 

 First kill it by means of any one of the killing bottles or boxes already 

 described, or by immersion in spirit of wine. When quite dead, 

 enlarge the anal orifice by thrusting a needle into it, and then lay 

 it on a piece of blotting paper with its head toward you. Now 

 take a round ruler, previously covered with blotting paper, and roll 

 the larva gently from head to tail till all the contents of the skin 

 have been expelled. Next fix the skin on the fine end of the blow- 

 pipe, by thrusting the point of the latter into the opening, and 

 allowing the spring to press gently on its edge. Gently blow into 

 the skin till it is inflated just to a little beloiv natural size, then 



K2 



