April, '09] JOURNAL OF ECONOMIC ENTOMOLOGY 91 



illumination and arrangement of background. For a large amount 

 of work it is preferable to obtain a photomicrographic stand. The 

 Bausch & Lomb Optical Company, of Rochester, N. Y., has produced 

 one of the best simple stands available for this work. This stand 

 is adjustable for inclination to any angle from horizontal to vertical, 

 and is provided with a 24 inch bellows, with adjustable lens board 

 and ground glass, and carries 4x5 inch plates. 



There are numerous lenses on the market which may be available 

 for enlarging work. The Bausch & Lomb firm has produced in their 

 Micro-Tessar series the best lenses for this work that are known to 

 the writer. The 72 mm. lens (nearly 3 inch focus), which is extremely 

 rapid, working at f-3.5, is the most serviceable one for ordinary 

 work. "With the above photomicrographic stand and 72 mm. lens, 

 photographs ranging from one-half natural size to 8 diameter enlarge- 

 ments can be secured. The 48 mm. and 32 mm. lenses are of higher 

 power. With the latter lens fitted in the above stand 20 diameter 

 enlargements can be made. 



The ordinary dissecting stand, with rack and pinion, will be found 

 very useful for focusing. A piece of plain glass to which has been 

 glued a cork fitting the lens holder of the dissecting microscope, can 

 be used for carrying the specimens. When the bellows has been ad- 

 justed at the proper length to secure the desired magnification, the 

 focusing can be done with the above arrangement without further 

 change of the bellows. 



Preparation of subject. — As before stated, the specimens may be 

 dry or immersed in a watch glass or shallow glass dish, the latter 

 method being applicable to larva^ or specimens in preservative fluids. 

 The fluid has a buoyant effect on the hairs or spines of various hairy 

 larvae, causing them to assume a more natural appearance while im- 

 mersed. To prevent shadows, loose specimens should be laid upon a 

 very clear, clean glass as above mentioned, with the background some 

 distance below. For pinned specimens a tiny piece of cork should be 

 glued to the glass plate, thus preventing any shadow from specimen 

 or pin. An old photographic plate, cleared of the film with sulphuric 

 acid, will furnish a good grade of glass for this purpose. 



Whenever possible the pins should be removed from the specimens 

 to be photographed. Where this is not advisable, the head of the pin 

 should be cut off and the cut end blackened with India ink. The pin 

 can be almost eliminated in a photograph if its axis is arranged to 

 coincide with the axis of vision. Specimens to be photographed 

 should be cleaned of any particles of dust or lint by means of a small 

 camel's hair brush. 



