'""*'! SitARLE, The Pond and its Inhabitants. 21 



1917 J ' 



the plant on which they were bom in search of other creatures 

 upon which to feed. Unlike the larvae of the beetles just 

 described, who have to come to the surface at intervals to 

 breathe, the larva of the dragon-fly is able to extract the 

 oxygen needed for respiration from the water, mucli in the 

 same manner as a fish does, but with this difference, that the 

 gills of the larva are in the end of its abdomen, the leaf-like 

 blades in which the abdomen terminates also probably acting 

 as external gills in many species. Being voracious feeders, 

 their bodies soon fill out, and after their first ecdysis, or moult, 

 the increase in size is very noticeable. It is provided with a 

 very remarkable organ for the capture of its prey. From its 

 position when at rest it is called a mask, as it covers the mouth 

 and front part of the head of the insect. Anatomically, it is 

 the lower lip of the insect, which has been modified into a 

 prehensile organ. It is jointed in such a manner that part of 

 it folds back rmder the chin, while the end with its claw-like 

 appendages fits closely over the front of the head. But should 

 some unfortunate insect come within striking distance, the 

 joints straighten out with lightning rapidity, and the insect 

 is clasped in its pincer-like extremity. The joints are then 

 folded back, and the larva, at its leisure, feeds on its prey. 



When describing the water-beetle we saw that its meta- 

 morphosis was complete — that is. that the full-grown larva 

 changed into an inactive pupa, from which in due time the 

 perfect beetle emerged. But in the dragon-fly the meta- 

 morphosis is incomplete — there is no resting stage in its life- 

 history^ the nymph, or pupa, being just as active and rapacious 

 as the larva, the difference in appearance being the gradual 

 growth of the wing-cases enclosing the rudimentary wings of 

 the future dragon-fly. When the time comes for the insect's 

 final change, the pupa creeps up the stem of a plant out of 

 the water, and, clasping the stem (nearly always the under side) 

 firmly with its legs, rests in this position until the outer skin 

 becomes dry and brittle, and soon, helped probably by the 

 muscular contraction of the insect, the skin splits down the 

 back, and through this opening the head, with its large com- 

 pound eyes, is drawn. The thorax and legs are next freed from 

 the pupa skin, and the newly-born insect, with soft, limp body 

 and crumpled wings, hangs head downwards from the pupa 

 case. Presently it begins to move its legs about, and grasping 

 the stem creeps up an inch or so, thus detaching the rest of the 

 abdomen from the pupa case, for which it has no iurther use. 

 While in this position the wings straighten out, dry, and 

 harden, and probably other most important changes are 

 taking place at the same time. 



We must remember that while the nymph was a pond- 



