88 THE MOSQUITOES OF NEW JERSEY 



and sometimes remain in the same position for days ; but would quickly 

 let go and wriggle away if disturbed. Before piercing the plant tissue 

 the larvae often move along a root, tipping the tube against it as if 

 feeling for a soft spot. After such a performance a favorable spot was 

 usually located in a crotch where a rootlet divided from the main 

 branch. 



Just how far the larvae go down into the swamp in winter, if they go 

 down below the point at which they were collected at all, is not known 

 at this time, and how the adult emerges from the pupa in late spring, 

 is also a question which cannot be answered at present. 



In collecting at Lahaway, November 10, I found that the heavy 

 rains had raised the July level of the small pond where I found the 

 egg boats over six inches, and that this had resulted in lifting the 

 bottom vegetation so that it floated, leaving about six inches of open 

 water between the bottom of the sod and the mud of the pond bot- 

 tom. By getting the net through the floating sod and sweeping the root 

 mass underneath, larvae were obtained in every dip ; but no larvae were 

 found in the bottom mud. The roots, then, are essential to the larvae 

 and they seem not to occur where none are present. This is also borne 

 out by the observations made by me in the Trenton swamps. 



Mansonia perturbans is probably the nastiest of the inland mosqui- 

 toes with which we have to deal. It has for its home just those kinds of 

 swamps that are free from other mosquito life, and probably also the 

 shallow borders of lakes which support a heavy vegetable growth. Such 

 places are usually well supplied with predaceous water insects as well as 

 other natural enemies of mosquito larvae and even Anopheles is unable 

 to maintain itself to any extent. But perturbans selects for its breeding 

 spots so thickly overgrown with vegetation that very few insects and no 

 fish are able to penetrate. Thus the egg boats are left unmolested and 

 the larvae as soon as hatched bore down into the mass of roots away 

 from all ordinary foes. Hard bottomed tussock swamps probably never 

 breed perturbans. Such swamps as are apparently bottomless, that is, 

 they are so boggy that solid footing cannot be gotten at any depth, 

 serve as the haunts of the larvae of that species. 



Owing to the fact that the larvae are not dependent upon atmos- 

 pheric air for their supply of oxygen, and that they penetrate silt for 

 some distance, they cannot be reached with the ordinary petroleum oils 

 and lime mixtures. Draining the swamp by means of deep ditches, or the 

 removal or thinning out of the vegetation to give fish and other enemies 

 an opportunity to enter would be the most effective method and, in the 

 long run, the least expensive in eradicating breeding areas. Nevertheless 



