POND LIFE. 



107 



to an insect that falls into the water where there are 

 water-striders ? 



6. Watch the water-striders and learn if they will 

 jump from the water to catch insects that fly near it. 



7. Remain quiet at the shore of the pond or 

 stream till the water-striders approach near enough 

 to be observed closely and determine what portions 

 of the body rest upon the water. 



8. Observe the dimples in the water where the 

 feet rest on the surface. 



9. When the sun is shining brightly, find some 

 water-striders where the water is shallow and ob- 

 serve on the bottom of the pool the shadows of the 

 dimples in the water made by the feet of the insects. 

 Note that each shadow is surrounded by a golden 

 ring of light. The more advanced pupils should be 

 able to explain the cause of this ring of light. Note 

 that there is no ring of light about the shadow cast 

 by the body ; why is this so ? 



10. Make a sketch showing the outline of the 

 body and the position of each of the legs and the an- 

 tennae when the insect is at rest. 



11. Discover which pair of legs are the chief 

 organs of locomotion in the striding of these insects. 



12. Collect as many kinds of water-striders as 

 possible, saving several specimens of each species. 

 Kill them in your cyanide bottle and then pin them 

 on your return home. 



Water-striders are dimorphic — that is, there are 

 two distinct forms of fully developed individuals in 

 each species. One form is winged, the other wing- 

 less. Try to procure both the winged and the wing- 

 less form of each species collected. The presence 



