Dec, 1920 Bulletin of the Brooklyn Entomological Society 137 



titles. Some years ago I tried some experiments on this point, 

 but failed owing to faulty technique. Just one experiment was 

 positive and seemed to indicate considerable carbon dioxide pres- 

 ent. This phase also needs further investigation. 



During the pupal period of histolysis a tremendous amount of 

 carbon dioxide and other wastes are accumulated and stored in 

 various ways, chiefly as carbonic acid and uric acid, and this is 

 voided shortly after ecdysis in the form of viscid, often colored 

 droppings, such as the brown, red, or green droppings of Chiro- 

 nomids, etc. These are usually acid in reaction, and the assump- 

 tion is that they are composed of carbonic acid, uric acid, and 

 other wastes. This is by no means clear, and needs further 

 attention. 



8. Storage of Air for Static Purposes. 



Most of the plastron insects, besides the sheet of air on their 

 sterna, store air under the elytra. The natural effect of the 

 sternal plastron would be to turn the insect upside down, be- 

 cause of the greater buoyancy of the air plastron. Brocher 

 working on beetles and Hemiptera found that buoyancy in the 

 upright position is due to the storage of air under the elytra. If 

 the air under the el37tra was removed the insect was unable to 

 maintain its proper position and was inverted. Brocher further 

 found that there is a delicate counterbalance between the amount 

 of air held for buoyancy and breathing and the weight of the 

 insect. In most cases the amount of air was sufficient to carry 

 the insects to the surface, so that if an insect were to remain sub- 

 merged it had to cling to some plant or other object to prevent 

 its ascent. 



Certain permanently water-breathing adult beetles (Elinis, 

 Stenelmis) have the power to increase or decrease the amount of 

 buoyant air and hence are able to raise or lower themselves at 

 will and to remain suspended in the water (Brocher). Air is 

 secreted and forced under the elytra and this automatically lifts 

 them in the water to any desired level. Suspension is most 

 highly developed in Corethra larvae. Corethra adjusts itself very 

 rapidly to change in pressure, requiring only a few minutes to 

 adjust to a decrease from 22 milligrams pressure to 10 mmg.. 



