N. J. Mosquito Extermination Association 73 



Table L 



Plants from Bayou Walnut, 1915. 



Species. Common Name. Location. 



Spirogyra sp., Algae, Submerged. 



Lemna valdiviana, Lemna 

 gibba, Spirodela polyrhiza 



and WolMa columbiana, . . . DuckAveed, Floating on water. 



Jussiaea diffusa, Aquatic plant, In water, roots in bed. 



Zizaniopsis miliacea, Aquatic grass, In water, roots in bed. 



Cephalanthus occidentalism ...Button-ball, In water, along margin. 



Salix nigra, Swamp willow, Margin, overhanging. 



Bignonia radicans, Trumpet-creeper, . . . Margin, overhanging. 



Brunnchia cirrhosa, Vine, Margin, overhanging. 



Persicaria opelusana, Smartweed, ..' Margin. 



Phytolacca americana, Pokeberry, Margin. 



Bchinochloa colona. Cockspur-grass, Margin. 



Asclepias pereniiis, Milkweed, Margin. 



Ampelopsis arborea, Shrub, Margin. 



Buphorbiaceae, Spurge, Margin 



A point of special interest in connection with the natural con- 

 ditions of the bayou is the fact that the top-minnow, Gamhusia 

 affinis, is found in connection with general breeding of Anopheles. 

 The breeding of these mosquitoes in the presence of compara- 

 tively large numbers of this minnow is accounted for by reason 

 of the protection aiforded the mosquito larvae by the aquatic and 

 marginal vegetation and the vegetable debris upon the surface of 

 the water. Further, the bayou under natural conditions is par- 

 tially dry at certain seasons of the year, and in these dry sections 

 there are isolated pools, mud-cracks and hoof-prints of animals, 

 which become filled with water by the rains, and to which these 

 fish do not have access. 



A comparison between the numbers of Gamhusia in the natural 

 bayou and in all other places shows an average of 25 specimens in 

 the bayou for each collection and an average of 63 per collection 

 for all other classes of surface water. These figures indicate that 

 these little fish are very abundant and very generally distributed 

 in the region. The larger numbers for all classes of water, as 

 compared with the natural bayou, is explained by the fact that 

 certain collections in the general survey were made at the season 

 of the year when the surface water was at a low stage, which 

 found these fish highly concentrated in some localities. 



The clearing of the bayou was done during August, 191 5. It 

 was accomplished at that time of the year for the reasons that the 

 water in the stream was at its lowest level for the season and the 



