92 Animal Micrology 



are floated out properly, then add more balsam, and put on. a 

 cover-glass. 



V. OPAQUE MOUNTS 



Some objects are mounted to be viewed by reflected instead of trans- 

 mitted light. They may be mounted in the ordinary way, and when 

 examined as opaque objects, the light from the mirror should be turned 

 away and, if necessary, a strip of dark paper placed under the slide to 

 shut off all light from below. 



A. Beetles. Choose a shallow cell for mounting the wing cases and 

 legs of one of the Curculionidae, preferably Curculio imperalis, the 

 South American diamond beetle. 



1. Soak the part in cedar oil or turpentine for half an hour, then 

 place it in the cell in the proper position, the outer side of the case 

 toward the observer. 



2. Fill up the cell with balsam and add the cover. 



B. Wings of Moths or Butterflies. Prepare parts of the wings of moths 

 or butterflies as in A. The wing of the clothes moth makes a good 

 opaque mount. 



C. Head of a Fly. 1. Secure the specimen (preferably one having 

 colored eyes, as one of the gad-flies) and choose a cell of the proper size 

 for it. The cell should be of such a depth that the cover will rest lightly 

 upon the object and retain it in the center of the cell. The head should 

 present the front view when mounted. 



2. Spin a very thin coat of gold size on to the dry edge of the cell so 

 that the cover will adhere. 



3. Soak the head of the fly for a couple of hours in equal parts of 

 glycerin and water. 



4. Moisten the cell by breathing into it, fill it with glycerin and 

 transfer the object to it. 



5. Breathe on the cover-glass and apply it very carefully to avoid 

 air-bubbles. When the cover settles into place, press it down gently to 

 make it adhere to the cement. 



6. Set it aside to harden. When hard, seal on the turntable with 

 gold-size followed by Bell's cement when the gold-size is dry. 



D. Foreleg of Dytiscus, the Great Water Beetle. 1. Detach the foreleg 

 of a male, and soak it in 10 per cent, potash solution (see Appendix B, 

 reagent 76) for a day or two. 



2. Wash it in water, run it up to 95 per cent, alcohol, and leave it 

 there for 24 hours. 



3. Pass it through absolute alcohol and clear in cedar oil, turpentine 

 or xylol. 



