AQUATIC LARV.E. 163 



according to the species, and forms an angle with 

 the last segment but one. The mouth of this 

 organ is funnel-shaped, and terminates in five 

 points like a star ; and by this it is usually sus- 

 pended at the surface of the water, 

 and preserves its communication with 

 the atmosphere. In its interior is a 

 tube which is connected with the 

 tracheae, and terminates in several 

 openings, visible under a microscope 

 at the mouth of the organ. The 

 points or rays of this mouth are used 

 to close it when the animal is dis- 

 posed to sink in the water, and thus 4*0*4* *t*j 



fY i i an aquatic Larva. 



cut on its communication with the 

 atmosphere. When the animal is immersed, a 

 globule of air remains attached to the end of the 

 tube, so that it is in fact of less specific gravity 

 than water, and it is not without some effort 

 that it descends to the bottom; but when it 

 wishes to rise again, it has only to unclose the 

 tube, and it rises without an effort to the surface, 

 and remains suspended for any length of time. 

 The extremity of the larva is clothed with bunches 

 of hairs, which are furnished with some repellent 



