INSECTS' EGGS 137 



check was placed upon their increase, all vegeta- 

 tion would soon be destroyed. Luckily, however, 

 there are numerous enemies that prey upon them. 

 Fig. 86 shows the pearly iridescent egg of one of 

 the hover-flies — wasp-like flies that are often seen 



Fig. 86. A]) egg of a hover-fly. ;■; 25 diameters 



poised by the rapid vibrations of their wings over 

 plants — these flies usually place their eggs singly 

 on stems and leaves amongst the aphides, and 

 when the voracious young larva of the hover-fly 

 emerges, woe unto those green-flies ! The larvae 

 of these flies are remarkable tor several curious 

 features, considering- the nature of their food. In 

 the first place, they are blind ; secondly, they are 

 footless ; and thirdly, they drop from leaf to 



