March, 1913.] GrOSSBECK: MosqUITOES AND ENVIRONMENT. 55 



and Philhydnis they are attached to plants and in Helocharcs are 

 carried on the abdomen until hatched. The cocoons are formed by 

 the secretions of two glands discovered by Stein. 



Differences in color in Hclophorus may be caused by the sur- 

 roundings; darker specimens are found late in the fall by sifting and 

 collecting in the woods, while lighter ones occur more in the open 

 field. The species prefer sandy shores of slow running water, but 

 are also found in stagnant water. 



I was fortunate enough to capture one specimen of Ochthcbius 

 foveicollis Lee. for the first time in New Jersey by sweeping in clear 

 stagnant water on MyriophyUiim. Most of the species are Pacific 

 and are said to prefer clear, running, shallow water, in which they 

 may be found adhering to the underside of stones, preferably those 

 partly out of water. Frequently they are found in small colonies. 



The species of Hydrccna are found here in stagnant water, but in 

 California are said to occur in clear brook water, not under stones 

 but in sand. 



THE RELATION OF MOSQUITOES TO THEIR 

 ENVIRONMENT. 



By John A. Grossbeck, 

 New York, N. Y. 



So far as known all mosquitoes are aquatic in their larval and 

 pupal stages. Only a comparatively few, however, are able to exist for 

 an indefinite period beneath the surface of the water, nearly all being 

 forced to rise periodically to the top for a supply of oxygen. For 

 this purpose a tube of varying length, according to the species, has 

 been developed in the larva, and a pair of them, differently placed 

 however, in the pupa. These tubes are in nearly all species thrust 

 through the surface film and oxygen is obtained by direct contact with 

 the outer air. In a few species, only one of which is found in the 

 vicinity of New York, these tubes have become modified for a wholly 

 underwater life. In these the tubes are so constructed that their 

 tips may be inserted into the roots of plants and air obtained from or 

 through the plants. In addition to the tube the larva is provided with 

 four tracheal gills situated at the anal end of the body, and in a very 



