SUCKERS OF INSECTS. 



201 



evolutions, which they frequently continue for hours together 

 with unwearied zest, while their far longer forefeet are no less 

 admirably formed for seizing their prey. 



Like them, the Hydrometridse may be met with in every pond 

 or stream, skimming along the surface, 

 and turning with the greatest rapidity. 

 The body is boat-shaped, the hind-feet 

 serving a a rudder ; while the two middle 

 feet brush along the surface of the water, 

 and give the required motion. The under 

 side of the body is clothed with a thick 

 coating of fine hairs, evidently intended to 

 prevent the insect from coming in contact 

 with the water. 



By means of the strong hooks or 

 claws with which their feec are usually 

 armed, most insects are able to climb with great facility on 

 a rough surface ; while others are provided with a more com- 

 plicated apparatus, which enables them to ascend vertically on 



Hydrometra stagnorum. 



Foot of Domestic Fly. 



Foot of Bibio febrilis. 



the surface of glass, or to remain suspended in an inverted 

 position from the ceiling. We have a familiar example in 

 the house-fly, which has the extremities of its feet furnished 

 with two funnel-shaped membranous suckers, moveable by 

 muscles in every direction, by which they are capable of ex- 

 hausting the air on very smooth surfaces thus causing the 

 pressure of the atmosphere to sustain the weight of the body. 

 The area of these suckers is so beautifully adjusted to the 



