302 



Marvels of Insect Life. 



the water and urge itself along ; but it can on occasion make a spurt in a double 

 sense by ejecting water forcibly from its breathing chamber in its hind-body, and 

 so propel itself. 



In the photograph of the nymph it will be seen that the hind-body terminates 

 in several wedge-shaped " tails " guarding the entrance to a chamber in which 

 is contained organs through which the blood courses, and through whose walls ox^^gen 

 dissolved in the water can be taken up by the blood. When the nymph expands 

 its hind-body these " tails " separate widely and the chamber is filled with a fresh 

 supply of water. Then the tails close up and constitute a valve, keeping the water 

 in. When the water is exhausted of its oxygen, the valve is opened, the water 

 ejected, and another supply taken in. If the nymph wishes to reach the other 



' side of the pond quickly, it has onlv to 

 eject the water under great pressure and 

 lift its feet, when the force of the outward 

 stream sends the nymph forward rapidly. 

 Another remarkable item in the struc- 

 ture of the dragon-fly nymph is the develop- 

 ment of its lower lip to almost half the 

 entire length of the body. But it is hinged 

 to the mouth and again near its middle, so 

 that when not in active use it can lie packed 

 close under the head. At its front this 

 structure ends in two curved hooks which 

 fit against the face like a mask. Creeping 

 quietly up towards its prey, it suddenly 

 extends this mask to its full length, secures 

 the victim with its hooks, and holds it close 

 against the real jaws whilst it is consumed. 

 We have elsewhere spoken of com- 

 plete and partial metamorphoses, and have 

 explained that where the food of the Insect 

 is of the same nature throughout life, 

 involving no change in the digestive system, 

 there is no need for a resting period 

 known as the chrysalis-stage. The dragon-fly is carnivorous throughout life : 

 therefore, its acquisition of wings is gradual as in the grasshoppers, and until it 

 leaves the water to fully develop these organs it leads an active life. 



After a year or two of this kind of life — the period varies in different species — 

 the nymph crawls up a water-plant that has aerial stems and climbs right out of 

 the water. Hooking its feet into the plant it takes firm hold, for it feels that 

 something important is going to happen. Of course, like other Insects, it has had 

 to moult several times in order to allow of an increase of size. Now the change 

 is to be not merely a more roomy jacket of the same pattern as the last, but some- 

 thing more striking. The skin of the fore-body splits above, and the Insect walks 

 out of it, the old shells of its feet retaining their hold of the plant. Its long hind-body 



Photos by] [H. Main, F.E.S. 



Egg-Capsules. 



The common cockroach lays her eggs in parcels of sixteen, 

 two rows of eight being enclosed in a horny capsule, which 

 is carried about by the female until she can find a suitable 

 crevice in which to hide it. The upper photograph shows the 

 capsule of the common species {" black-beetle "), the lower 

 that of the smaller " croton-bug." 



