92 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 2 



Illumination. — Various radiants may be used for illuminating the 

 object to be photographed, namely, — sun, calcium, electric, gas, or 

 kerosene light, named in the order of their actinic power. In using 

 daylight, north or east light is preferable for photographic work of 

 this kind. Specimens photographed in direct sunlight frequently 

 cause reflections and halation on the sensitive plate, and hence it is 

 not so satisfactory as a more subdued constant light. To secure even 

 illumination on all sides of an object where the light is admitted at 

 but one side of the room, the entire apparatus may be suspended so 

 that it may be revolved during the exposure of the plate. Special 

 light may be thrown upon any portion or all of an object by means 

 of a concave mirror such as is provided with the ordinary compound 

 microscope ; or a paraboloid lens may be used to concentrate the light. 

 A softer light reflected from a half cylinder of white paper is often 

 more 'desirable. 



Background. — Faulty and imperfect backgrounds ruin the appear- 

 ance of more amateur pictures than any other of the minor defects. 

 If the glass plate mentioned above is always used, with the background 

 either white or black, at some distance below, perfect negatives with- 

 out shadows may be secured. The best black background can be made 

 by lining a deep box with black velvet, or dull black paper such as is 

 used in packing photographic plates. Covers to the box with orifices 

 of various sizes to suit the specimens add to the intense blackness of 

 its interior. In case a black background is used great care in arrang- 

 ing the specimens on the glass plate is necessary to prevent accumula- 

 tion of bits of dust or lint. Such particles of dust or lint are strongly 

 reproduced on the black background, though scarcely visible on a 

 white background. 



Plates.^ — Any of the standard plates are good for this work, but 

 special brands are preferred by some. Seed's Gilt Edge No. 27, a 

 very rapid plate costing a few cents more per dozen than others, has 

 given complete satisfaction. A slow plate may be preferable in many 

 cases, but where time is a factor a fast plate is a time saver, especially 

 in photomicrography, where exposures of several minutes are often 

 necessary. Orthochromatic, color corrected and non-halation double 

 coated plates often give better results than the ordinary single coated 

 plates. It should be remembered that one-half strength developer 

 should be used on double coated plates. 



Developer. — A most satisfactory single solution non-staining plate 

 and film developer which will keep indefinitely in stoppered bottles, 

 and may also be used for developing Velox and kindred papers, can 



