VORACITY OF jVIAGGOTS. 



271 



elevates into the air, that he may not be disturbed with 

 its struggles, and soon devours. Tlic havoc which 

 these grubs make amongst the aphides is astonishing. 

 It was but last week that I observed the top of every 

 young shoot of the currant-trees in my garden curled 

 up by myriads ot' these insects. On examining them 

 this day, not an individual remained; but beneath 

 each leaf are three or four full-fed Itrvae of aphidivor- 

 •ous f^ics, surrounded with heaps o' the skins of the 

 slain, tlie tro|)iues of their successful warfare.''*- 



Tile larvie of the lace-winged flies {Hcmevobidce, 

 Leach) are even more destructive to the aphides than 

 either of the preceding; insomuch tiat R aumur was 

 induced to call them the lions of tie aphides. The 

 mandibles of the larva of Hemerob us are somewhat 

 crescent-shaped, and, like those of the ant-lion, are 

 hollow, by means of which they sack the juices of 

 their victims. U'hese are rarely so numerous as the 

 two preceding families, but they nake up for their 

 fewness in the voracity with which they devour the 

 little destroyers of our vegetables. 



Intr. i, 264. 



I.aee-wiiiged fly ; 4, the grub of the same, magnified ; c, 

 syiphus ; d, larva of the same devouriig the aphidea of the eld- 

 n ; I, the head magnified, to show the mouth. 



