78 



Dragon-flies and Damsel-flies 



streams impregnated with sulphur from sulphur springs. Nor do dragon- 

 flies like cold weather. Although a few species are found in the far North 

 (recorded at 70° N. in Norway, 65° N. in Alaska, and 63° N. in Siberia) 

 and a few at high cold altitudes (as high as 10,000 feet) on mountain flanks, 

 the great majority of them need considerable temperature for growth and 

 development and even for activity during adult life. Calvert says that but 

 one species is known which regularly pa.s.ses the winter in adult stage, and 



that most dragon-flies live as adults from 

 but twenty-five to forty-five days, and 

 these in the summer. In California, where 

 the winter temperature at sea-level only 

 occasionally falls to 32° F., adult dragon- 

 flies can be found in most of the months 

 of the year. 



The adult dragon-llies are to be seen 



pursuing their prey, like hawks, with 



//llljlfl ^S^^i r-^a. swift darting flights over ponds, along 



'Liu\f/« l'^^^^^-^. streams, and even scattered widely inland 



over fields and in woods. A few kinds 

 have a liking for the vicinity of houses. 

 Needham, a careful student of these 

 insects, has found that the hunting region 

 above arid along the shores of a pond may 

 be imaginarily divided into zones one 

 above the other, each zone characterized 

 by the presence of a few particular 

 dragon-fly species. "So, in fact," he writes, "we find the smaller damsel- 

 flies flying over the water in a straight course an inch or less above the 

 surface, and rarely venturing higher; the larger damsel-flies a little higher; 

 the amber wings at an average of about si.\ inches; the larger skimmers 

 a foot or more from the surface, and upland skimmers and darters still 

 higher. One has only to stand a little while by .some small area of water 

 where all these are flying to see that each keeps rather closely to his proper 

 altitude. Why do damsel-flies keep so close to water? The reason is 

 not far to seek. Dragon-flics cat one another — the strong destroy the 

 weak. If to venture up into the altitude of the larger species means to run 

 the risk of being eaten, we can readily see why the damsel-flies should 

 stay down below. The hawk may roam the air at will, but sparrows must 

 keep to the bushes." 



We think of dragon-flies, as of albatrosses and Mother Carey's chickens, 

 as being always on the wing. They catch their prey while flying, eat it 

 while flying, mate while flying, and some of them deposit their eggs while 



Fin. 113. — Oamsel-flies (narrow- 

 winged dragon-flies). (Natural 

 size; from life.) 



