MISCELLANEOUS NOTES. 885 



purpose and making traction upon both wings at the same time. The legs 

 are now carefully arranged and put down into the celloidin solution on the 

 cover slip, more solution being added if necessary. 



If the legs have fallen into the celloidin solution before the wings have 

 been arranged in their proper places, a little careful manipulation with the 

 needles will enable one to pass the wings under the legs or vice versa and a 

 few final touches to the antennse, etc., will bring all the parts into their 

 proper relation. 



Another drop of celloidin solution is now put over the specimen, which is 

 then allowed to dry. After about half an hour a further drop of the solu- 

 tion is placed over the thorax, and this again is allowed to become nearly 

 dry. 



This specimen is then ready for mounting, either in ordinary balsam, or 

 in the mixture of zinc oxide and balsam, which is less liable to penetrate 

 the celloidin than ordinary balsam, and at the same time shows up the 

 points of the specimen to advantage. 



To prepare this zinc balsam, the zinc oxide should be sifted through fine 

 muslin and a sufficient quantity added very gradually to xylol balsam until 

 a thick uniform opaque white mixture has been obtained. 



A big drop of this zinc balsam is placed in the hollow of a slide, which is 

 then inverted upon the specimen ready prepared on the cover slip. The 

 hollow of the slide prevents the crushing of the specimen and saves the 

 bulky thorax from damage. 



Although an advantage, hollow slides may be dispensed with, if the 

 thorax of the fixed mosquito is carefully snipped off by means of a pair of 

 fine iris scissors. 



As zinc balsam takes some time to harden, specimens should be kept face 

 downwards for several days until hardening has taken place. 



Pkecautions. 



Strength of celloidin solution to be used. — This will depend largely upon the 

 atmospheric conditions, a weaker solution being necessary when drying is 

 rapid. The point to be aimed at is to obtain a solution which will allow 

 sufficient time for manipulating the specimens with needles, and at the 

 same time will afford an adequate coating. 



The tendency at first will be to use too strong a solution of celloidin. 

 Ethereal solution should on no account be used, as the rapid evaporation 

 leads to the formation of air bubbles which ruin the specimen. 



Drying of the specimen before mounting. — If the specimen be allowed to dry 

 for too long before the final mounting, the contraction of the celloidin will 

 result in the formation of cracks through which the balsam will subsequently 

 penetrate, or it may be found that separation of the mosquito from the sur- 

 face of the cover slip is taking place. 

 43 



