418 MEDICAL ENTOMOLOGY 



eggs. The formalin is then allowed to flow out, and as it does so it 

 leaves the eggs adhering to the sides of the tube, with a film of the 

 solution. The ends of the tube are then sealed in the flame in the 

 ordinary manner, so that the formalin cannot evaporate any further. 

 For most purposes the eggs can be examined sufficiently well through the 

 glass, but if a closer examination under a high power is required, they 

 may be washed out of the tube with five per cent, formalin. If a fairly 

 long piece of capillary tube is left at each end the same one can be 

 used after it has been opened several times ; care should be taken to cut 

 the tube with a file before attempting to break it. 



Larvae of diptera should be taken just before they become full grown, 

 but while still feeding, as the shape is apt to alter the last day or so 



. before pupation. They are best killed by dropping 



Larvae and pupae , 



them into boiling seventy percent alcohol, as this stret- 

 ches them out. The alcohol is heated in a small evaporating basin or 

 frying pan, thus minimizing the danger of it catching fire. The speci- 

 mens should then be transferred to fresh seventy per cent alcohol, and 

 preserved in small specimen tubes, the corks of which should be sealed 

 with paraffin. The spirit should be renewed every three months and 

 fresh corks inserted. A slip of paper with the details of the age, 

 species, where taken, etc., written in pencil should be placed in the 

 tube. Small larvae may be dehydrated, cleared in clove oil, and mounted 

 in Canada balsam. The cover slip may be supported, if necessary, with 

 fragments of glass or with two pieces of fine capillary tubing, in order to 

 prevent the cover slip from pressing on the specimen. Pupae can be 

 preserved in the same way as larvae. The puparia of the Muscidae 

 are best mounted on slips of card which may be pinned next to the 

 imagines in the store box. 



It is frequently necessary to make special preparations of particular 

 parts of the fly for purposes of identification, as for instance the exter- 

 nal genitalia of Glossina and Phlebotoimts ; the wings of the latter, the 

 heads of mosquitoe larvae, etc. The method of making cleared prepara- 

 tions is fully described in Chapter XL 



The isolated worker is often at a loss to know to whom to send his 

 specimens of blood-sucking diptera for identification. The following 

 addresses of well-known experts on each of the families and genera may 

 be found useful. 



Ceratopogoninae ... Professor J. J. Kieffer, Bitsch, Germany. 

 Simulium ... Professor Mario Bezzi, via Pio Quinto, No. 3, 



Torino, Italy. 



