84 



Dragon-flies and Damsel-flies 



each female. Needham counted 1 10,000 eggs in a single egg-mass of Libellula. 

 Sometimes the eggs may be laid on wet mud or attached to moist water- or 

 shore-jjlants. The damsel-flies and a few of the dragon-flies insert the eggs 

 in the stems of dead or living water-plants below the surface of the water. 

 To do this they have to cling to the stem, with the abdomen or sometimes 

 the whole body under water, and cut slits in it with the sharp ovipositor. 

 The eggs are sometimes laid on submerged timbers and moss- or alga-covered 

 stones. Kellicott observed females of A rgia putrida (a damsel-fly abundant 

 along Lake Erie) to remain wholly under water for from five to fifty-five 

 minutes at a time. These females were accompanied by males which also 

 stayed under for similar lengths of time. 



The eggs hatch after various periods, depending on the species of dragon- 

 fly and on the time of year of oviposition. In midsummer Needham found 

 the eggs of some species to hatch in from six to 

 ten days, while others laid in autumn did not hatch 

 until the following spring. In the same lot of eggs 

 the period of incubation may vary even in midsum- 

 mer from a week to more than a month. 



From the eggs come tiny, spider-like nymphs 

 with long, slender legs, thin body, and no sign of 

 wings. Even in the largest dragon-fly species the 

 just-hatched young are only about one-twelfth of 

 an inch long, while the nymphs of the common 

 Libellulas are only one-twenty-fifth of an inch long 

 at hatching. They begin their predatory life, con- 

 fining their attention at first to the smaller acjuatic 

 creatures, but with increasing size and strength 

 and confidence being ready to attack almost any of 

 the under-water dwellers. Even fish are seized by 



Fig. 115. — The young jj,g larger nvmphs, Needham having seen the 

 {nymph) of a damsel- , r ' 



fly (narrow-winged dra- nymphs of one species seize and devour young 



gon-fly), Usies sp. The brook-trout as long as themselves. 



three leaf-like processes _,, . ,.„ . . ,.„ . , 



at the tip of the abdo- The young of different species dilTer consider- 



men are gills (Twice ably in size, shape, and duration of their nymphal 

 na ura size.) e.xistence. The nymphs of some species require 



more than a year to develo]) into adults, while those of some others arc ready 

 to transform in a few months, not a few dragon-fly species having two gener- 

 ations a year. The one-year life cycle, however, is usual among the more 

 familiar dragon-flies, the eggs laid during midsummer hatching in late sum- 

 mer, the nym])hs hibernating and being ready to emerge the following sum- 

 mer. Needham thinks that the damsel-flies have a number of broods in 

 a season, the processes of transformation and oviposition beginning as soon 



