86 PROCEEDINGS OF THE NATIONAL MUSEUM. 



for study Working with such small insects, it is difficult to arvangc 

 them satisfactorily upon the slide, but with patience and care this can 

 be accomplished fairly well. The wings shouhl V,e spread, and this 

 condition has, as a rule, been most easily obtained by transferring the 

 insect from the xvlol to the center of a clean slide, and then teasing 

 the wings out to the desired position by means of a tine bristle. The 

 balsam is then placed on the cover and gently lowered onto the insect 

 As the balsam spreads it tends to carry out the wings, legs, and 

 antennae so that they are in a position for study. It is a conveniencr 

 in study to have two specimens on the same slide, one ])eing dorsal, 

 the other ventral side up. Specimens of different species should not 

 be placed upon the same slide. If it is desired to keep a large nun. 

 ber of duplicates, it is not, perhaps, advisable to mount them all u. 

 this way, as they can be fairly well preserved by placing the living 

 insects ^directlv in about 80 per cent alcohol. Alcohol is, however, 

 liable or even likely, to cause an abnormal distension of the body, 

 especially wi^h Tubulifera, and if some of these distended specmiens 

 are afterwards mounted permanently for study it Nvill be found that 

 their o-eneral appearance has become so changed that the species is 

 scarcely recognizable. For this reason I can recommend alcohol only 

 for duplicates of well known species and never for undescribed 



material. 



While balsam mounts, made as described, seem to be best tor pre- I 

 serving the general natural appearance of the insect, mounts made in 

 anothel- way are more useful for study of the chitinous structur.^ 

 Everything but the chitin is dissolved by allowing the specimen to 

 mascerate for from twenty-four to thirty-six hours in a cold 1»> per 

 cent solution of caustic potash, or by boiling for a few minutes in a 

 little of the same solution. When thoroughly cleared the specimen 

 may be mounted directly in glycerin, or washed in water, dehydrated 

 in alcohol followed by xylol, and then mounted in balsam. Such 

 mounts can be examined under high-power lenses and reveal many ■ 

 fine details of chitinous structure which can not be seen m ordinary ^ 



mounts. . 



A few words in regard to glycerin mounts may save some one such 

 disappointment and loss as my experience with them has caused me. 

 During one summer quite a large number of mounts were made by 

 placing the insect directly into glycerin contained in a low cell, made 

 either^of white zinc cement or hard glycerin jelly, the cover ghis^ 

 being carefully sealed on with the white zinc cement in each case. 

 Thei. mounts were beautifully clear at first and were placed aside for 

 study during the winter. When examined again after a few months 

 they were found to be ruined and worthless. Nearly every specimen 

 was more or less thickly covered, especially around the spiracles and 

 thin membranous areas, with dense clusters of white, needle-like 



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