Dec, 1920 Bulletin of the Brooklyn Entomological Society 131 



THE RESPIRATION OF AQUATIC INSECTS. 

 A Collective Review. 



By Richard A. Muttkowski, Ph.D., University of Idaho. 

 {Continued from page g6.) 



5. External Oxygenation. 



(a) At the Surface. — External oxygenation is related to sur- 

 face-breathing. It is needful to consider the latter. Most in- 

 sects of this type must come to the surface at some time or other 

 for their oxygen. Many take the air directly into the body by 

 means of the caudal spiracles (larvae of Dytiscidse, Hydrophil- 

 idse, Stratiomyia, etc.), others form a plastron of air on the un- 

 derside and also store it under the elytra (adults of Coleoptera, 

 Corixa and Notonecta, nymphs of the latter two on the under- 

 side). The devices for clinging to the surface of the water while 

 breathing atmospheric air are too well known to need repetition. 

 But in surface-breathing the question of accidental entry of oil 

 and water through the caudal spiracles is important. It is prob- 

 ably a little known fact that dragonflies in the last instars are able 

 to breathe with their thoracic spiracles and wander freely from 

 both media (air and. water) without difficulty. In some experi- 

 ments with various insects in studying defensive devices against 

 oil and water Portier found that hydrofuge surfaces and special 

 absorptive tissues are the chief means of defense. The Odonata, 

 however, have thoracic spiracles which permit the entry of neither 

 oil nor water; that is, they are both oleofuge and aquifuge. In 

 the case of hydrofuge surfaces it has been found that mere con- 

 tact with oil will destroy the effectiveness of that surface. Hence, 

 it is not surprising that although the caudal spiracles of so many 

 aquatic larvae are 'surrounded with hydrofuge surfaces, oil and 

 water may get it in spite of these surfaces. (The chief means of 

 mosquito control is based on the foregoing principle.) In the 

 case of the Odonata the superposition of hydrofuge and oleofuge 

 surfaces in the form of superposed plates prevents the entry of 

 either oil or water (Portier). 



