ENTOMOLOGICAL NEWS. 



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PHILADELPHIA, PA., APRIL, 1900. 



In January, 1891, through the kindness of Mr. Julius F. 

 Sachse, a well-known scientific and literary gentlemen of this 

 city, we published a half-tone of the larva of Cithcronia n-oalis. 

 As far as we know this was the first time that this process of 

 photography had ever been used in a natural history journal. 

 Since then the use of half-tones for illustrative purposes has 

 become general. In December, 1891, we also published "A 

 Suggestion for a Possible Method of Identifying the Colors 

 Photographed." This work was also done by Mr. Sachse and 

 was a step in advance. Since 1891 photographic processes 

 have been improved in various ways, and in this number we 

 give illustrations of the so-called three-color process. Three 

 negatives of the objects are made, each one through a different 

 'color screen," respectively, red, yellow and blue. Three 

 half-tones are then made from these negatives, and then by 

 making an impression on the paper from each half-tone block, 

 and using for each block one of the three inks yellow, red 

 blue the perfect print is obtained. Great care must be taken 

 in registering the blocks, so that each color shall properly 

 cover the figures. The process is a wonderful one and is 

 beautifully adapted for natural history work, as it gives me- 

 chanically correct maculation and is practically correct for 

 color. This is our first plate of the kind, and was made here 

 in Philadelphia. 



