970 The American Naturalist. [ November, 
Directions for Collecting Insects.—Dr. C. V. Riley has pre- 
pared and the National Museum has published (Bulletin No. 39, Part 
F), an admirable pamphlet entitled Directions for Collecting and 
Preserving Insects. It contains 147 pages and almost as many illus- 
trations, and covers the field in a thorough and systematic manner. 
It will prove invaluable to all young entomologists, and there are few 
older ones who cannot derive useful hints from it. 
Number of Insect Species.—In the introductory portion of 
the bulletin just referred to Dr. Riley writes: “ The omnipresence of 
insects is known and felt by all; yet few have any accurate idea of 
the actual numbers existing, so that some figures will not prove unin- 
teresting in this connection. Taking the lists of described species and 
the estimates of specialists in the different orders, it is safe to say that 
about 30,000 species have already been described from North Amer- 
ica, while the number of species already described or to be described 
in the Biologia Centrali-A mericana, i. e., for Central America, foot up 
just about the same number, Lord Walsingham having estimated them 
at 30,114 in his address as President of the London Entomological 
Society two years ago, neither the Orthoptera nor the Neuroptera 
being included in this estimate. By way of contrast the number of 
mammals, birds, and reptiles to be described from the same region is 
interesting. It foots up 1937, as follows: 
“Mammals, 180; birds, 1600; reptiles, 157. 
“If we endeavor to get some estimate of the number of insects that 
occur in the whole world, the most satisfactory estimates will be found 
in the address just alluded to and in that of Dr. David Sharp before 
the same society. Linnzeus knew nearly 3000 species, of which more 
than 2000 were European and over 800 exotic. The estimate of Dr. 
John Day in 1853 of the number of species on the globe was 250,000. 
Dr. Sharp’s estimate thirty years later was between 500,000 and 
1,000,000. Sharps and Walsingham’s estimates in 1889 reached 
nearly 2,000,000, and the average number of insects annually de- 
scribed since the publication of the Zoological Record, deducting 8 
per cent for synonyms, is 6500 species. I think the estimate of 2,000,- 
000 species in the world is extremely low, and if we take into consid- 
eration the fact that species have been best worked up in the more 
temperate portions of the globe, and that in the more tropical portions 
a vast number of species still remain to be characterized and named, 
and if we take further into consideration the fact that many portions — 
of the globe are yet unexplored entomologically, that even in the 
