IX 



DRAGON-FLIES 34i 



crept an inch or two out of the water they return 

 thither, after taking a breath of air ; but those which 

 have made a longer excursion, it may be several feet 

 upon the land, and especially those which are found 

 clinging fast to stems or branches, are making ready 

 to cast their skin and to become flies. 



" I have found larvae belonging to the same species 

 which underwent their transformation an hour or two 

 after issuing from the water, while others passed a 

 whole day before liberation. The operation takes 

 some time, but the observer will be so much occupied 

 by the interest of the details, that he will not willingly 

 leave it half finished. One can read, so to speak, in 

 the eyes of the larva, whether it is ready for trans- 

 formation or not. Within a quarter or half an hour 

 of the time of liberation the eyes, which were pre- 

 viously dull and opaque, become bright and trans- 

 parent. This change does not really take place in 

 the larval eyes themselves, but is due to the pressing 

 close against them of the eyes of the fly, which have 

 already acquired all their brilliancy. 



" In order to enjoy again and again the spectacle 

 of the transformation, it is desirable to collect a con- 

 siderable number of larvae of the same species and 

 to keep them in water. When the cast skins show 

 that some of the flies have emerged, the margin of 

 the water should be searched at different hours of the 

 day for larvae which have crept out. They commonly 

 rest some time in order to dry themselves thoroughh^ 

 before proceeding further. At length the larva begins 

 to seek a place convenient for its operations. It often 

 grasps a plant and holds on to it with its head 



