m 



COLLECTING DEAGON AND MAY FLIES — NEEDHAM. 



The resident collector who knows the season of flight for any com- 

 mon species may get nymphs of that species by going out at the begin- 

 ning of its season and picking them up as they crawl from the water. 

 If on going out the first time he finds the most recently emerged ima- 

 goes are ready to fly, he must go again at an earlier hour. 



The invitation to collect by this method comes oftenest from the flut- 

 tering of a limp and half-colored imago before one's feet. Near to the 

 place whence this one was flushed and in similar places one may look 

 with some confidence for others still in process of transformation. 

 This method alone will not satisfy the thoroughgoing collector, but, 

 because he may sometimes accumulate a large amount of valuable 

 material in a few minutes and with no more apparatus than may be 

 carried in a single pocket, it deserves to be better known. 



REAEING NYMPHS. 



The best way to rear nymphs is to let them rear themselves. Locate 

 them, collect a few from time to time to watch their growth, preserve 

 the young ones for specimens, and do not take any for rearing until 

 about grown. Their development can be gauged by the length of the 

 wing cases. For species that seem common, and that live in accessible 

 places, there is no advantage in early collecting; they will seem to 

 become more common as the season of their transformation approaches, 

 because, first, they get larger and are more readily seen; and, secondly, 

 they approach the margin of the water and are more easily taken. 



The best rearing device is the one that keeps, its inmates under con- 

 ditions most nearly natural. A cage for aquatic insects that hardly 

 disturbs such conditions at all con- 

 sists of a cylinder of galvanized wire 

 screen, open at both ends, having 

 a loose screen cover with a rim of 

 heavy wire. One end of the cylinder 

 is pushed down into the mud of the 

 bottom in shallow water, the cover 

 is laid on and all is ready. Such a 

 cage merely incloses a small water 

 area with its natural vegetation, 

 and nymphs placed inside live their 

 natural lives and obtain for them- 

 selves their accustomed food. Of 



course the size of the mesh must be adapted to that of the insects to 

 be reared — small enough to confine them and large enough to admit 

 their x)rey. Fifteen inches is a convenient height. 



For burrowing nymphs it will be necessary to set the lower edge of 

 the cage down into the mud of the bottom 2 or 3 inches; this is easily 

 done with a garden trowel. 



It is better, owing to danger from freshets, not to plant such a cage 

 in the rapids in the direct course of a stream, biit to divert a small arm 



Fig. 4. — Cage for rearing nymphs under natu- 

 ral conditions. 



