384 



Handbook of Nature-Study 



their size. The dragon-fly's eggs are laid in the water; in some 



instances they are simply dropped and sink 

 to the bottom; but in the case of damsel-flies, the 

 mother punctures the stems of aquatic plants and 

 places the eggs within them. The nymph in no 

 wise resembles the parent dragon-fly. It is a 

 dingy little creature, with six queer, spider-like 

 legs and no wings; although there are four little 

 wing-pads extending down its back, which encase 

 the growing wings. It may remain hidden in the 

 rubbish at the bottom of the pond or may cling 

 to water weeds at the sides, for different species 

 have different habits. But in them all we find a 

 most amazing lower lip. This is so large that it 

 covers the lower part of the face like a mask, and 

 when folded back reaches down between the front 

 legs. It is in reality a grappling organ with hooks 

 and spines for holding prey; it is hinged in such a 

 manner that it can be thrust out far beyond the 

 head to seize some insect, unsuspecting of danger. 

 These nymphs move so slowly and look so much 

 like their background, that they are always 

 practically in ambush awaiting their victims. 



The breathing of the dragon-fly nymphs is peculiar; there is an 

 enlargement of the rear end of the alimentary canal, in the walls of which 

 tracheae or breathing tubes extend in all directions. The nymph draws 

 water into this cavity and then expels it, thus bathing the tracheae with 

 the air mixed with water and purifying the air within them. Expelling 

 the water so forcibly, propels the nymph ahead, so this act serves as a 

 method of swimming as well as of breath- 

 ing. Damsel-fly nymphs, on the other 

 hand, have at the rear end of the body, 

 three long, plate-like gills, each ramified 

 with tracheae. 



Nymphs grow by shedding the skin 

 as fast as it becomes too small; and when 

 finally ready to emerge, they crawl up on 

 some object out of the water, and molt for 

 the last time, and are thereafter swift 

 creatures of the air. 



References — American Insects, Kellogg. 

 Comstock's Manual 



Nymph of a damsel-fly. 

 Outdoor Studies, Needham. 



Nymph of a dragon-fly. 



Seen from the side, showing the position 



of the great lower Hp when folded 



beneath the head. 



From Outdoor Studies, Needha m. 



LESSON LXXXV 



The Dragon-flies and Damsel-flies 



Leading thought — ^The dragon-flies are among the swiftest of all winged 

 creatures and their rapid, darting flight enables them to hawk their prey, 

 which consists of other flying insects. Their first stages are passed in the 

 bottoms of ponds where they feed voraciously on aquatic creatures. The 

 dragon-flies are beneficial to us because, when very young and when full 

 grown, they feed largely upon mosquitoes. 



