362 INSECTS. 



pupa case of this insect may be frequently found attached 

 to the leaves which the larva (whose skin now forms this 

 pupa case) has but lately cleared of the infesting Aphides. 

 The larva is a slimy, whitish, slug-like, or rather leech- 

 like grub, with a curious habit of seizing its victim and 

 holding it raised in the air until all its juices are ex- 

 tracted. 



The many genera which this family contains present 

 numberless varieties in form, colours, and marking. 

 Thus, as described above, some are Bee-like in form, 

 others compact, with oval or nearly globular abdomen, 

 others are long and narrow, and others again have a 

 somewhat club-shaped abdomen (see PI. XV., fig. 5, 

 Melithneptus menastri). In some of the more slender 

 species, the thighs are swollen, giving the Fly the appear- 

 ance of a leaping insect ; others have peculiar tarsi. 

 The colours also vary : they are black and yellow, black 

 and dull red, black and white, black and grey. Some 

 species are black only, others lustrous and metallic, while 

 others have black and green, yellow, or metallic and 

 glittering heads with black and yellow banded bodies. 



Notwithstanding all these variations in form and 

 colour, there are characters which make it easy to dis- 

 tinguish the Syrphidae. The head is convex in front 

 and flat behind, so as to be nearly all face a large round 

 face almost covered by the eyes, which are especially 

 large in the males. The tongue, which is large and well 

 developed,* is bent about the middle when at rest, and 

 the front of the head sometimes forms a sort of pro- 

 jecting beak or snout (very conspicuous in a large, dull, 

 red Fly, the Rhingia rostrata. The antennae are, almost 



* The tongue of the larger Syrphidae is one of the most beautiful and 

 most easily prepared for the microscope, of the tongues of the Diptera. 



