THE UrMENSE N"UMBER OF IN-9ECTS. 13 



immense, and the new species that are being continnally added to our 

 lists, as the results of an increased number of observers, more thorough 

 collections, and more extended explorations, is constantly enlarging 

 tlie estimate which naturalists from time to time present of the proba- 

 ble number occurring throughout the world. The discovery of new 

 Ibrms is ever in advance of the ability of entomologists to give them 

 description, name, and classification. There are to-day in the British 

 Museum no less than 12,000 species remaining undescribed, and like 

 un worked material is to be found in every collection of any extent in 

 both hemispheres. Fifty years ago, 70,000 species had been described, 

 and it was then thought that there were at least twice that number in 

 existence. The scientific activity of the past half century has more 

 than quadrupled that number, and there are now 330,000 de- 

 scribed species. In view of this rapid increase, it will not be safe to 

 assume that even yet one-half of the actual number have been de- 

 scribed. From our present knowledge, and from the vast extent of the 

 globe which is still, in natural science, terra iiicognita, it does not seem 

 improbable that the number of insects in the world may reach a mil- 

 lion of sperAes. 



Leaving the species and passing to individuals — if we proceed to a 

 calculation of number, we almost question the results shown by our 

 figures. Dr. Fitch has given us a computation of the number of 

 cherry-tree aphids — Aphis cerasi Yixhw — occurring upon some trees 

 upon his grounds. He writes:* "Among the cherry-trees alluded 

 to, was a row of seven young ones which had attained a height of about 

 ten feet. By counting the number of leaves upon some of the limbs 

 and the number of limbs upon the tree, I find a small cherry-tree of 

 the size above stated is clothed with about seventeen thousand leaves. 

 These loaves could not have averaged less than five or six hundred lice 

 upon each, and there was fully a third more occupying the stems and 

 the tips of the twigs. Each of these small trees was, therefore, stocked 

 with at least twelve millions of these creatures," 



Even our knowledge of insect fecundity fails to explain such wonder- 

 ful multiplication, and our reason cannot assign the 2:>urpose for which 

 such seeming excess is designed. It is related of a little midge {Chiron- 

 oinus nivoriuudus), that, on one occasion, in traversing a forest it was 

 observed in such countless myriads as to prove of the greatest annoy- 

 ance to the tourist, getting into Ixis mouth, nostrils, and ears at every 

 step, and literally covering his clothing, f 



The Rocky Mountain locust, in its migratory flights, hides the sun, 

 and fills the air as far as tlie eyft can reach. From the highest peaks 



* Fird mid Second Report on the Insects of New York, lS5i5, p. \'2T. 

 +Fitch : Winter Insects of Eastern New York ; Ainer. Jour. Agr.-Sci., v, 1S4G, p. 2S2. 



