10 Journal New York Entomological Society. tVoi. xxi. 



of the water serves to drive the larva forward in the water, a method 

 of swimming found otherwise in jellyfishes, cephalopods and salps. 

 The larvae of the demoiselles swim by an undulatory movement of 

 the body. 



The habits of the larvae vary considerably. Those of the demoi- 

 selles and certain of the larger forms, especially of the ^shninas, 

 climb about among water plants, and such forms are usually green- 

 colored as a protective adaptation. The larvae of the Gomphinae and 

 Libellulinae wander over the bottom, or partially or entirely bury 

 themselves in the mud and muck. These are brownish or gray, 

 neutral-colored forms and are usually covered more or less by par- 

 ticles of the debris among which they live. Many species are widely 

 distributed and are found in almost all sorts of localities, appearing 

 to have no special choice as to whether they inhabit streams or ponds. 

 Other species, again, are limited to particular habitats, such as spring- 

 fed brooks, rapid creeks or stagnant ponds and marshes. Some of the 

 species mature in a year, others, it is said, spend as long as three 

 years in the larval condition. 



Numerous species are known to breed in brackish water, and, as 

 the writer has shown (American Naturalist, Vol. XL, June, 1906, 

 pp. 395-9), they are capable of withstanding a salinity equal to about 

 half that of pure sea-water. Schwarz ("Preliminary Remarks on 

 the Insect Fauna of the Great Salt Lake, Utah," Canadian Entomol- 

 ogist, Vol. XXIII) has also recorded certain species as inhabiting 

 salt and sulphurous ponds in Utah, and the writer has observed others 

 in slightly alkaline ponds in North Dakota. These same species breed 

 also in pure fresh water and some of them are distributed from coast 

 to coast. Two species, Erythrodiplax berenice and Ischnura rani- 

 hurii, are restricted to a coastwise distribution along the Atlantic and 

 Gulf of Mexico. The exact reasons why these forms that may breed 

 in brackish water are unable to breed in water having a higher salin- 

 ity, such as pure sea-water, has not been determined. 



Before the time of transformation the larvae often crawl out of the 

 water for brief periods, breathing by means of the spiracles, and when 

 the time has arrived for shedding the larval skin the insect crawls 

 out upon the bank or upon a stick or waterplant projecting above the 

 surface, splits down the back of the thorax and emerges in the winged 

 condition. The adults of the larger species are, as a rule, strong 



