260 ENTOMOLOGICAL NEWS. [July, 'l8 



local habitat, but my good friend, Wm. T. Davis, of Staten 

 Island, New York, wbo has taken these insects in numbers, 

 assures me that this is not a tree species. The following quo- 

 tation is from a recent letter from him on this question: "I 

 have collected a great many females of the Manoincra that 

 occurs about New York, and have seen a great many more 

 that I let stay in the low vegetation, so that they might not 

 be exterminated. I have always found the insects on golden 

 rods, Asters and such like plants, and can assure you that it 

 isn't a tree species." This conforms with the known habitat 

 of more western material and seems to make rather sure the 

 determination of these eastern specimens as blatchlcvi. It is 

 certainly singular that among the somewhat ample material 

 of Atlantic Coast specimens found in various eastern collec- 

 tions not a single male is to be found. Can it be that this in- 

 dicates parthenogenesis ? 



The Lake Mosquito, Mansonia titillans Walk., and 

 its Host Plant, Pistia stratiotes Linn., in the Canal 

 Zone, Panama (Dip. : Culicidae)."" 



By L. H. DUNN, formerly Entomologist of Board of Health 



Laboratory, Ancon, Canal Zone. 



That the formation of Gatun Lake introduced new elements 

 creating prominent changes in the flora and insect fauna of 

 the Canal Zone, Panama, is manifest beyond all doubt. Prior 

 to the beginning of the construction of the Gatun Dam and 

 the Spillway, the area now covered by the lake was traversed 

 by the swift-flowing Chagres River and the numerous smaller 

 rivers forming its tributaries. The Chagres afforded good 

 drainage throughout its valley with the exception of a low 

 marshy area south of Gatun. This area was known as the 

 "Black Swamp." It was several square miles in extent and 

 of irregular formation. In the dry season this region con- 

 sisted of a series of small lakes, pools and sluggish streams. 



* Read before the Medical Association of the Isthmian Canal Zone, 

 January 18, 1918. 



