PREHENSION OF LIQUID FOOD. 



87 



ordinary mouth, a tube also provided for suction, in a dif- 

 ferent part of the body, and leading into the same stomach.* 

 When the instrument for suction extends for some length 

 from the mouth, it is generally termed a proboscis: such is 

 the apparatus of the butterfly, the moth, the gnat, the house 

 fly, and other insects that subsist on fluid aliment. The pro- 

 boscis of the Lejjidoptera, (Fig. 266,) is a double tube, con- 

 structed by the two edges being rolled 

 longitudinally till they meet in the 

 middle of the lower surface, thus form- 

 ing a tube on each side, but leaving 

 also another tube, intermediate to the 

 two lateral ones. This middle tube is 

 formed by the junction of two grooves, 

 which, by the aid of a curious appara- 

 tus of hooks, resembling those of the 

 laminae of a feather already described,! 

 lock into each other, and can be either 

 united into an air tight canal, or be instantly separated at 

 the pleasure of the animal. Reaumur conceives that the 

 lateral tubes are intended for the reception of air, while the 

 central canal is that which conveys the honey, which the 

 insect sucks from flowers, by suddenly unrolling the spiral 

 coil, into which the proboscis is usually folded, and darting 

 it into the nectary.! 



In the Hemiptera, the proboscis is a tube, either straight 

 or jointed, guarded by a sheath, and acting like a pump. 

 The Diptera have a more complicated instrument for suc- 

 tion, consisting of a tube, of which the sides are Mrong and 

 fleshy, and moveable in every direction, like the trunk of 

 an elephant: it has at its extremity a double fold, resemb- 

 ling lips, which are well adapted for suction. The gnat, and 

 other insects which pierce the skin of animals, have, for this 

 purpose, instruments, termed, from their shape and ofiice, 



* Phil. Trans, for 1822, 442. 



•f Volume i. p. 393. 



\ Kirby and Spcnce's Entomology, vol. ii, p. 390. 



