[7] COLLECTING AND PKESEEVING INSECTS RILEY. 



insects and how to study them becomes important, almost necessary, 

 to every farmer. 



The scope of the science may best be indicated by a statement of the 

 number of species existing, as compared witli other animals. The 

 omnipresence of insects is known and felt by all ; yet few have any ac- 

 curate idea of the actual numbers existing, so that some iigures will not 

 prove uninteresting 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 thirty thousand species have already been described 

 from North America, while the number of species already described or 

 to be described in the Biologia Centrali- Americana, i. e., for Central 

 America, foot up just about the same number. Lord Walsingham hav- 

 iug estimated them at 30,114 in his address as j)resident of the Loudon 

 Entomological Societj" two years ago, neither the Orthoptera nor the 

 ISTeuroptera being included in this estiniate. By way of contrast the 

 number of mammals, birds, and reptiles to be described from the same 

 region, is interesting. It foots up 1,937, as follows : 



Mammals, 180; birds, 1,600; reptiles, 157. 



If we endevor 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. Linnaeus knew nearly 3,000 species, of which more than 

 2,000 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. Sharif's 

 and Walsingham's estimates in 1889 reached nearly 2,000,000, and the 

 average number of insects annually described since the imblication 

 of the Zoological Eecord, deducting 8 per cent for synonyms, is 6,500 

 species. I think the estimate of 2,000,000 species in the world is ex- 

 tremely low, and if we take into consideration the fact that species 

 have been best worked ui) in the more temperate i)ortious 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 con- 

 sideration the fact that many portions of the globe are yet unexplored, 

 eutomologically, that even in the best worked up regions by far the 

 larger portion of the Micro-Hymenoptera and Micro-Diptera remain 

 absolutely undescribed in our collections, and have been but very par- 

 tially collected, it will be safe to estimate that not one-fifth of the 

 species extant have yet been characterized or enumerated. In this 

 view of the case the species in our collections, whether described or un- 

 described, do not represent perhaps more than one-fifth of the whole. 

 In other words, to say that there are 10,000,000 species of insects in 

 the world, would be, in my judgment, a moderate estimate. 



