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. An egg of a hover-fly, x 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 for 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 



