EXTRAORDINARY ABUNDANCE 135 



At first sight these figures appear overwhelming; in fact, however, they are 

 insignificant. It must be remembered that the mosquitoes in a barrel are of all 

 stages, from egg to pupa, and that only a very small proportion reach maturity 

 each day. The greater the number of larvse present in a barrel the slower will 

 be their development, on account of the limited food supply, and it is by no means 

 certain that anywhere near all the larvae in such a barrel ever attain the adult 

 state. Moreover the above figures appear exaggerated; thus counts by others 

 show an average, in some cases of about 200 eggs, in other cases less, in the egg- 

 masses of the common species.* Experience has shown us that the amount of 

 annoyance to the inhabitants of a house, from the mosquitoes of a single well- 

 stocked rain-water barrel, is not so great as would be thought, and beyond a very 

 limited area there is no perceptible effect. 



One of us (Knab) has observed a case of extraordinary abundance of Culex 

 pipiens at Urbana, Illinois, due to unusual breeding facilities. A creek in the 

 vicinity of the town is practically stagnant in the late summer. At a certain 

 point this creek received the waste from an abattoir and, as a result, for some 

 distance was so charged with decomposing animal matter that no fish could 

 live in it. In this strongly polluted water immense numbers of Culex larvae 

 throve. They were so numerous that their breathing-tubes produced the appear- 

 ance of a scum upon the surface of the water. The imagos covered the foliage 

 of the trees and bushes along the stream ; they were present in millions and they 

 continued to reproduce until cut off by cold weather. Yet their presence was 

 not felt at even a short distance, and very few of these mosquitoes found their 

 way into the town — perhaps a mile away. 



Thus it will be seen that great mosquito abundance in any region is not the 

 result of the accumulated products of successive generations but the practically 

 simultaneous development of large numbers over a wide area. 



MOSQUITOES IN THE FAR NORTH. 



As is well known, mosquitoes abound, for a short season, even in arctic regions. 

 The writers have made a number of efforts to secure good mosquito material 

 from the arctic regions, but very few specimens have been sent in, so it has been 

 impossible to study the species. As a matter of fact, mosquitoes seem to be even 

 more numerous in individuals in the far north than they are in certain parts of 

 the tropics; in the tropics, on the other hand, there is a very much greater 

 variety and very many more species. Many accounts of arctic exploration and 

 of travels in the far north dwell upon the extraordinary abundance and ferocity 

 of the mosquitoes during the short arctic summer. Such accounts are merely 

 a part of the record of the travellers' experiences and are almost wholly prompted 

 by the discomforts endured. They contribute practically nothing beyond the 

 facts which were forced upon the travellers — abundance and ferocity. 



That mosquitoes should develop in such extraordinary numbers in the arctic 

 regions seems remarkable when we consider the extreme brevity of the summer 

 season. In fact, however, it is this brevity of the summer which brings about 



• Weber, S. E. : Entom. News, v. 17, pp. 214-217 ; Davis, J. J. : IMd., p. 369. 



