330 



Marvels of Insect Life. 



a minute what may have taken the green-fly hours to pump up through its hair-fine 

 sucking apparatus. All day, and night, too, for about ten days the hover-fly grub 

 pursues this course, and destroys many hundreds of green-fly. Then it feels it has 

 reached the end of its labours. 



It now attaches itself to the stem of the plant, contracts its length, and the 

 skin becomes taut and polished. In shape it becomes much like a grape-stone. 

 \A'ithin, the grub has turned to a chrysalis, from which it emerges about ten days 

 later as a black and yellow banded fly. These are bright little creatures, and they 

 may be seen frequently with their wings at rest upon flowers, when they are engaged 

 in feeding upon pollen and nectar. When so engaged, their characteristic markings 

 and the very distinct arrangement of the wing-nervures may be closely examined 

 bv those who have no desire to capture them, but to studv the living Insects. For 



this purpose no flowers offer a better 



opportunity than those of the Michael- 

 mas-daisies in gardens, which swarm 

 with various species of hover-flies. 

 Most of them bear either bands or 

 spots of yellow on a black ground, 

 and those that differ from this style 

 of colouring may be detected bv the 

 wing-neuration. What this is may 

 be learned much better from a glance 

 at the photograph of the pear-tree 

 hover-flv ^ on this page than from 

 any detailed description. 



A singular fact about these flics 

 is that the mouth is furnished with 

 cutting lancets, as though they were 

 blood-sucking flies requiring instru- 

 ments for cutting the skin of the 

 higher animals ; but we believe they 

 have never been known to draw blood. 

 Such a type of mouth is not the best 

 fitted either for sucking up nectar 

 or for eating pollen. It is probable that some important habit in which the lancets 

 are brought into use awaits the discovery of keener observers tlian have yet applied 

 themselves to its study. 



The eggs are laid singly, alwa\'s in the ncighbourliood of green-llw 

 is badly infested with these pests, many eggs may be laid upon it, but 

 be distributed over all the affected leaves, the stem, and the flowers 

 the green-fly are on these parts. An estimate of the work accomplished may be 

 formed by a sight of the empty green-fly skins still adhering to the plant, but many 

 of them fall to the ground when the hover-flv grub casts them awa\-. 



We have many species of hover-fly, but though they may difter in detail, what 

 we have described applies in general to them all. 



Photo hyl 



[E. Step, F.L.S. 



Pear-Tree Hover-Fly. 



A common species enlarged four times. It has tlie yellow and 

 black banding of the hind-body common to all the species. 

 Another feature shared by them all is well exemplified in this 

 photograph — the pecuhar pattern formed by the nerves of the wings. 

 The hind-body, too, when viewed from the side will be foimd to 

 be excessively thin. 



If a plant 

 they will 

 jorovided 



Catabomba jniastri. 



