1891-92-] Dragon-Flies : their Life-History. 5 



expelled from the tube. There are also the periodical expan- 

 sions and contractions of the abdomen, in which the breadth is 

 slightly increased and the length slightly lessened, indicating 

 the regularity of the function if the currents cannot be seen. 

 When lying quiet and undisturbed, these movements, I find, 

 number about thirty-two to the minute, but should the insect 

 be disturbed and excited they are much quickened. The 

 power of this wonderful apparatus is twofold. It not only 

 primarily carries on respiration, but at the same time it 

 enables the animal to progress at pleasure by swimming as 

 well as by crawling. Its method of swimming, however, is 

 somewhat jerky, though swift, as the expulsions are not con- 

 stant, there being a pause between every stroke of the internal 

 piston for the inrush of water. The legs are not adapted for 

 swimming, and do not assist in this mode of progression, being- 

 kept close to the sides of the body. On taking the larva out 

 of the water for a little, the respiratory action immediately 

 ceases, but on replacing it, the water is expelled or respired 

 with much more force than usual — equal, I would suppose, to a 

 gasping for breath, accompanied, on regaining the water, by a 

 slight clicking noise. The larvae, however, do not all respire 

 in this way. In the Agrionidae they do so by three flattened 

 plates or false gills, very like leaves, attached to the extremity 

 of the abdomen. Their edges, like leaves, are serrated, but only 

 half-way down, with a sharp prickle or hair at each point. 

 These plates are ramified by tracheae which extract air from 

 the water and convey it to the larger internal tracheae. They 

 also at the same time assist in locomotion. In Calopteryx 

 they are excessively long, nearly equalling the abdomen. 



An idea of the tenacity of life in the larvae may be had 

 from the fact, that after I had placed three, in different stages 

 of development, in methylated spirit, for one hour, they re- 

 gained their ordinary activity on being retransferred to fresh 

 water, and lived thereafter for a couple of days until finally 

 placed in spirit. 



On the approach of the great transformation, the pupa of 

 the dragon-fly crawls out of the water, and fixes itself by its 

 claws to some water-plant or other object, and makes ready 

 for the final ordeal. Within a longer or shorter time, the 

 pupa- skin once more splits along the back ; but on this occa- 



