Litter to tin Surgeon (leuernl of the Army accompanying eleven miscellaneous photographs of inserts mill 
ports of insects. 
Ah mv Medical Museum, 
January 20, 1872. 
BRIGADIER GENERAL .J. Iv. BARNES, 
Surgeon General. I'. S. Army. 
General: I transmit herewith prints of eleven miscellaneous photographs, of insects and parts of 
insects, made during the late Christmas holidays under the circumstances explained in my letter accompa- 
nying certain photographs of the Mosquito. 
The following is a brief description of the present series. 
No. 1. Clawed Water-bug (larva of Xaucoris cancroid es) magnified 19 diameters. Negative No. 
503, new series. This is the aquatic larva of an hemipterous insect. The posterior four legs are used in 
swimming. Anteriorly are two powerful grasping claws. 
No. 2. Sailor beetle (a species of Jlydroporus ) magnified 19 diameters. Negative No. 504, new 
series This is a small carniverous aquatic beetle. The preparation was so yellow that many details are 
lost, but the head with its forceps-like mandibles or jaws and its many jointed antenme, the anterior dense 
wing cases or elytra;, the posterior more delicate wings, and the six legs are tolerably well indicated. 
No. 3. Head of beetle magnified 15 diameters. Negative No. 513, new series. In this view of the 
head and anterior portion of the body of an unidentified beetle (probably a species of Tenebrio ) the toothed 
forceps-like mandibles, and the jointed antennae are more plainly shown. The mandibles or jaws of these 
insects work sideways, and not as in vertebrates up and down. They- are flanked by the jointed palpi or 
maxillary feelers, while externally the many jointed antenna) come into view. 
No. 4. Part of the Eye of a beetle, magnified 400 diameters. Negative No. 517, new series. Few 
objects connected with entomology are more wonderful than the compound eyes of insects. The optic 
nerves instead of leading to vast numbers of rods and cones united into a siugle layer as in the eyes 
of the higher animals, terminate in a rather smaller number of cones and rods, each of which corres- 
ponds to a separate lens covered by a separate hexagonal segment of cornea. Considerably over a hundred 
of these segments are shown in the photograph, which represents a very small portion of one of the 
compound eyes. The precise number has been differently estimated by entomologists but in many species 
amounts to several thousands. 
No. 5. Foot of Cockchafer (. Melolontha vulgaris ) magnified 80 diameters. Negative No. 514, new 
series. This beetle, so famous in the child-literature of Europe, is interesting in many particulars. The 
specimen from which the present photograph was taken serves to exhibit the anchor-like terminal hooks of 
one of the legs. 
No. 0. Belted Wasp-fly ( Syrphus balteatus') magnified 12 diameters. Negative No. 511, new series. 
This small but graceful fly exhibits at a glance many of the characters of dipterous insects. The head 
bears two long jointed antennae between which projects a needle like lancet or sting. The sucking tube 
to which this lancet belongs has been displaced in making the preparation and is seen externally to the 
left antennas. 
No. 7. Buccal organs of llmiey-bee (Apis mellijica) magnified 38 diameters. Negative No. 51G. 
4 he photograph exhibits the following parts. Centrally is seen the long flexible tongue or 
new series. 
