CHAP. XX 



SIALIDAE 



445 



orl-fly, and in "\Vales the humpback. It is very unattractive in 

 appearance, being of a blackish colour, with wings of a 

 yellow-brown tinge, and makes but a poor show when flying. 

 The female deposits patches of elongate eggs, placed on end and 

 packed together in a very clever manner (Fig. 287). These patches 

 of eggs, of a stone-gray colour, are common objects on rushes 

 or stems of grass near water, and it is stated that there may 

 be no less than 2000 or 3000 eggs in one of them. Our 

 figure gives some idea of the mode in which the eggs are arranged, 



FIG. 287. Portion of a row of eggs of 

 Sialis lutaria. (After Evaiis.) 



FIG. 288. Sialis lutaria, 



larva. 



and the curious narrow process that exists at the end of each. 

 The eggs are said to be sometimes placed at a considerable distance 

 from water, so that when the tiny larvae are hatched they 

 must begin their lives by finding the way to a suitable pool or 

 stream. The larvae (Fig. 288) are objects of very great interest 

 owing to each of segments 1 to 7 of the hind body being furnished 

 on each side with a jointed filament, while the last segment ends 

 in a still longer, but unjointed process. These filaments are 

 branchiae by means of which the Insect obtains air, being, as we 

 have said, destitute of spiracles. It is an active creature and 

 waves its filaments in a very graceful manner ; this process no 

 doubt aids the branchiae in their respiratory work. These larvae 

 are well able to exist out of water if they have a sufficiently 

 damp environment. They live on animal matter, but their life- 

 history has not been followed in much detail and it is not known 



