CENSUS OF INSECTS. 



Dr. Imhoff, of Basle, has made an estimate of the number of insects now 

 known, and such as, in all probability, may yet be discovered. In the first in- 

 stance, he establishes a comparison between the number of insects mentioned in 

 different faunas — and particularly Stephens' Catalogue of British Insects — with 

 the probable number of insects now known, or yet to be found, in Germany. The 

 sum total of this comparison gives, according to Stephens, 9,791 for Great 

 Britain, and for Germany, according to the Doctor, 14,000 species. 



To arrive at a general result, Dr. Imhoff does not think it advisable to esti- 

 mate the number of insects as compared with species of plants, but he has chosen 

 reptiles, as a class of animals with which the comparison may more fairly be calcu- 

 lated. Admitting, therefore, that in Germany there exist thirty-five or forty 

 species of reptiles, and on the surface of the globe 1,500, that is, nearly forty 

 times the number ' of those in Germany, the application of this system of compa- 

 rison would give for the insect tribes the number of 560,000, being 14,000 multi- 

 plied by 40 ; an mount considerably short of the probable number of insects inha- 

 biting the world, since at least 2,500, or perhaps more, may be added to Stephens' 

 Catalogue. 



To this calculation we add those of some eminent entomologists, in order to 

 prove, as far as analogous reasoning goes, that something approximating a pro- 

 bable reality may be inferred by taking a medium or averaged computation. 

 Linneus, in his Swedish Fauna, 1761, described 1,700 species, and in the 

 twelfth edition of the Systema Natural the entire number of these animals, in- 

 cluding the Swedish and exotic species, he was then acquainted with, amounted to 

 3000. Since his time, however, and more particularly during the last half cen- 

 tury, the study of entomology has received such an impetus, that Mr. Leay, in his 

 Hor« Entomological, states that there are certainly more than 100,000 annulose 

 animals preserved in various cabinets, nearly synonymous with the Linnean insects. 



Dr. Burmeister, whose census of insects is the most recent, takes his point of 

 comparison with known plants, by which it will be seen that Dr. Imhoff's calcula- 

 tion produces a larger amount of insect creation, though we think even his numbers 

 short of the reality. In Germany, Burmeister states there are about 6,000 plants, 

 including Cryptogamia, and upwards of 12,000 insects ; thus, if the proportion 

 be a constant one, the number of insects known, according to the 60 — 70,000 

 described plants, will amount to 120 — 140,000 species ; and if the generally re- 

 ceived opinion of modern botanists is adopted, that only about a third of the col- 

 lective species of plants is known, the number of species inhabiting the earth 

 would amount to 360 — 420,000 species of insects. 



The venerable Kirby, in his calculation of the number of insect species, as- 

 sumes that there are, on an average, six species of insects to one phanerogamous 



