— 157— 



in a decapitated Periplanata. (This idea had been previously advanced 

 by Dr. Packard. Anier. Nat. iv, 1870, p. ). 



6. Insects have no special organ of smell. 



The studies of Ecner, communicated to the Vienna Academy in 

 1875, led to the rejection of t!ie mosaic theory of vision in insects as 

 necessarily attendant upon their compound eyes, and to its replacement 

 by the theoretical deduction that they do not distinguish the form of 

 objects, but that their vision consists mainly in the perception of move- 

 ments and of colors. Their facetted eyes are not complete visual organs, 

 but simple organs of orientation. 



In a subsequent communication by Plateau to the Rciyal Academv 

 of Belgium, he has presented the following conclusions drawn from 

 studies of Diptera, Hymenoptera. Lepidoptera. Odonata and Coleoptera. 



In diurnal insects with compound eyes, the simple eyes offer so 

 little utility, that it is right to consider them as rudimentary organs. 



Insects with compound eyes do not notice differences of form exist- 

 ing between two light orifices, and are deceived by an excess of luminous 

 intensity as well as by the apparent excess of surface. In short, they do 

 not distinguish the form of objects, or if they do, distinguish them very 

 badly (Amer. Naturalist, xx, p. 69). 



The structure of the halteres of Diptera has been studied bv Mr. A. 

 B. Lee, who finds them to embrace two distinct organs, one an auditory 

 organ, and the other of problematical function, which may be olfactory 

 (Entomologische Nachrichten, for August, 1885). 



Sir John Lubbock records as an instance of remarkable longevity in 

 ants, that two queens oi Formica fusca had been kept alive by him with- 

 in their nests for twelve years (Contemporary Review, for Nov., 1885). 



Returning to our own country, unmistakable evidence of rapid 

 progress in our science is to be found in the explorations by private indi- 

 viduals, institutions and government surveys, of almost every portion of 

 our country for unknown species and the prompt study of the material 

 obtained, by competent specialists. 



Our lists of species are rapidly augmenting. 



In a paper recently read by me, not yet published, on the Present 

 Status of Etitomoloi;ical ScieJice in the United Stites, I had occasion to 

 state the number (as near as could be) of the described species of North 

 American Insects, North of Mexico. As it contained some estimates 

 made for the paper, it may be of interest to present the table at the 

 present time. 



Entomoloi^ica Americana. 22 Oct. & Nov. iii86. 



