94 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 2 



can be cut to fit in the end of the bellows nearest to the plate, but 

 never to be used in the plate holder. 



In ease one is using the ordinary photomicrographic stand it is 

 very convenient, by means of tAvo millimeter rules, to ascertain and 

 mark upon a stick just the exact bellows length required for various 

 enlargements for the various lenses at hand. In this way much time 

 will be saved, since the length of bellows for any desired enlarge- 

 ment can be readily determined. 



Photomicrography 



The same photomicrographic stand mentioned above is available 

 for this work, but no special lenses excepting those furnished with 

 the compound microscope are absolutely necessary. The objectives 

 and oculars furnished with the microscopes of years ago were not 

 properly corrected for photomicrographic work, but very good work 

 can be done with the lenses of very recent years without purchasing 

 special photomicrographic lenses. The object to be photographed 

 should first be focused through the microscope in the ordinary man- 

 ner, and the lower diaphragm should be stopped down to the light 

 which is best for ordinary examination of the specimen. The micro- 

 scope is then placed beneath the bellows and the hood attached to the 

 tube, and by shortening or lengthening the bellows, the image can 

 be arranged at the proper size on the ground glass. The amount of 

 light passing through the high power lenses is so slight that a focus- 

 ing glass is absolutely necessary to see the image. It is frequently 

 necessary to refocus the microscope so as to bring the object into 

 sharp outline on the ground glass. Then by stopping down the lower 

 diaphragm slightly and reducing the light, a greater depth of focus 

 can be obtained, although requiring much longer exposure to obtain 

 a good negative. In order to obtain the greatest depth of focus pos- 

 sible, it is advisable to use the lowest power objective which is suit- 

 able, and a long bellows rather than a short bellows and a high power 

 objective for the same picture. 



Better results can frequently be obtained by the use of stained 

 specimens. The stain should be one of the colors which will repro- 

 duce in black on the sensitive plate, the red tints being preferable. 

 The plate which has been exposed for a photomicrograph should be 

 developed rather slowly and carried to the limit, being careful lest 

 in overdeveloping detail may be lost. 



A ]\Iember : I wish to ask how you avoid reflections in alcoholic 

 specimens from the blacks. 



