clxiv GENERAL SUMMARY OF SCIENTIFIC AND 



jDlates, forming Vol. X. of Hayden's reports of the United States 

 Geological and Geographical Survey of the Territories. The de- 

 scriptive portion is preceded by chapters on the anatomy of the 

 head and thorax, on secondary sexual characters, etc:, while the 

 volume closes with an essay on the geographical distribution of 

 the species in this country. 



It is generally supposed that, while the tropics abound in large, 

 strong insects, there are not so many kinds like those of temperate 

 regions small and of modest colors. It appears, however, that the 

 number of small forms is as great as in the temperate zone. For ex- 

 ample, of the family of Rove beetles (Staphylinidae) Dr. Sharpe esti- 

 mates the probable number existing in the valley of the Amazon at 

 from 4000 to 5000. And Mr. H. W. Bates, who spent several years 

 (we believe nine) on the Amazon, states his belief that the propor- 

 tion the smaller forms bear to the larger is as great in Brazil as in 

 Europe ; but the larger forms were, of course, more commonly cap- 

 tured in a country where so many new and fine si^ecies were to be 

 found. 



New observations on the mode of respiration of the water-boat- 

 man {Notonecta undulata) have been i3ublished by the writer, in 

 '' Half- Hours with Insects." This insect is boat-shaped, the keel 

 of the boat being its back, the deck its ventral aspect. Along the 

 middle of the underside of the body is a longitudinal ridge ; a broad 

 gutter between this ridge and the sharp edge of the body is bridged 

 over from the head to the abdomen by a layer of dark, coarse, oblique 

 hairs, and a layer of less oblique hairs arises on each side from the 

 middle of the ridge. These hairs thus form a false upper deck. 

 The creature rises to the surfjice, the end of the body projecting 

 slightly out of water ; the air passes up on each side along the tun- 

 nel under the hairs, and collects in bubbles above the base of the 

 legs. Along the bottom of this tunnel are six pairs of spiracles into 

 which the air passes. The air in the specimens he observed did not 

 adhere to the hairs of the hind-legs, as Siebold says it does, nor, as 

 he states in his " Comparative Anatomy," translated by Burnett, does 

 the air for respiration as a rule pass under the elytra, since the spir- 

 acles are not situated on the upper side of the body, but on the un- 

 der, and quite a distance from the edge of the body. Nor does this 

 insect breathe at all, as Westwood states, like Dytiscus, in which 

 the spiracles are situated on the upper side of the body, so that the 

 air enters readily under the elytra. When it takes in the air, the tip 

 of the abdomen is thrust up just above water, and an orifice is formed 

 by the separation of the hairs at the end of the keel, which form the 

 larger part of the mouth of the orifice, the remainder being com- 

 posed of the hairs fringing the movable terminal plates of the bodj^ 

 The air thus passes in between the false deck of hairs and the under 

 side of the body. When the insect is taken out of the water the 



