BEETLES. 299 



one authoi'ity to be species will be only varieties in the estimation of another equally 

 able coleopterologist. Gemminger and Harold's catalogue of the Coleoptera of the 

 world, issued in parts between 1868 and 1876, contains 77,008 species described up to 

 the time of issue. Counting omissions from this catalogue, and species described 

 since its publication, the nuiAber of described species must jiow reach or exceed 

 100,000. In large collections there are, in all probability, between 20,000 and 30,000 

 more species still waiting description, and it would be rash to predict the number of 

 species which will be found later in parts of the world as yet insufficiently explored. 

 In North America, north of Mexico, Crotch's list, published in 1874, enumerates 7,450 

 species, and Mr. S. Ilenshaw, who has a manuscrij)t catalogue of beetles of the above 

 region kept up to date, informs me that the number is now (1884) about 8,950. 



Species of insects which feed upon substances of commercial value belonging to 

 one region are often transported, in one way or another, to other regions, where it is 

 not uncommon that these immigrants become serious pests until their natural enemies 

 are also imported, or until predaceous animals of their new home resort to them for a 

 food supply. Thus the Colorado potato-beetle {Doryphora decemlineata) has spread 

 from its original habitat in Colorado over the eastern United States, and its advent in 

 Europe is so greatly feared that it has been a subject of legislation in several coun- 

 tries. Our troublesome carpet-beetle (Anthrenus scrophularice) was jDrobably intro- 

 duced from Europe, and the asparagus-beetle of Europe ( Crioceris asparagi) was an 

 immigrant that landed on Long Island, near New York city, some time about 1860, 

 and has since done considerable damage to the market gardens which supply New 

 York city. So, too, the meal-beetle !( 7fe?ie5rio moKtor), and the grain-weevil {Calan- 

 dra oryzce) are of European origin. A few species of beetles have become, by mi- 

 gi-ation, almost cosmopolitan, but the greater number of species are confined to one 

 continent, often to some small part of a continent, although beetles are found in every 

 part of the world that has been explored. 



In geological distribution Coleoptera have been found as early as the carboniferous ; 

 they are more common, in Jurassic strata, and still better represented in the tertiary 

 and in amber. 



The modes of collecting and preparing beetles for the cabinet are very varied. 

 The beginner usually depends for specimens upon lucky finds, upon captures with the 

 net, and upon such modes of collecting as are used for all kinds of insects, and which 

 are described in most general works on entomology, while the experienced coleop- 

 terist studies the habits of rarer insects, and uses baits and traps to ensnare them. 

 Some of the less-known and useful ways of obtaining Coleoptera ior the cabinet are 

 the following. Beetles and their larvae which inhabit dung, earth, or other materials 

 heavier than water, float to the Surface of water, and can be easily discovered if the 

 earth or dung be broken up and placed in still pools, or in a trough filled with water. 

 For killing many kinds of beetles a ' cyanide bottle ' is very useful : this bottle is 

 made by putting a few pieces of potassic cyanide into the bottom of a lai-ge-mouthed 

 bottle — a horse-radish bottle will do very well, if no larger one can be found — and 

 covering the pieces of cyanide with dry plaster of paris ; after the plaster has been 

 evened down by shaking the bottle a little, water should be added, best a spray from 

 an atomizer. When the plaster sets a firm shell will be formed, which will hold the 

 cyanide in its place, while its poisonous vapors will slowly escape through the plaster. 

 If the moistened and subsequently hardened portion of the plaster is only about as 

 thick as is the glass of the bottle itself, a condition of affaii-s which can be regulated 



