582 STATE BOARD OF AGRICULTURE. 



no appreciably measurable amount would be given off again when once 

 it had passed into the insect. 



Continued respiration in oxygen was no more rapid than in air. 



The oxygen used for these experiments was obtained either from 

 electrolysis of water or by the use of "Oxoue" (i. e., fused sodium per- 

 oxide) and water. 



Now, when air or oxygen was transferred to insects previously con- 

 fined for several hours in carbon dioxide, nitrogen or hydrogen, it 

 should be noted that the first rapid exchange of gases took place while 

 the insects were lying entirely helpless without any noticeable respira- 

 tory movements. Visable proof of the passage of oxygen (without the 

 aid of respiratory movements) into insects was obtained in the follow- 

 ing manner: The wing covers of specimens of P. cornutus were re- 

 moved and nearly one-half cubic centimeter of a saturated solution of 

 Indigo Carmine was injected through a fine hypodermic needle, into 

 the body cavity of each. The insects were then put into glass con- 

 tainers in pure carbon dioxide, so as to exclude all oxygen. At that 

 time the abdomens, as seen from above, were intensely dark blue. After 

 twelve to fourteen hours without air, however, the tissues had reduced 

 all the Indigo Carmine to its leuco compound and the internal organs 

 of the beetles could be seen again (through the dorsal sui'face) en- 

 tirel}^ white to yellowish white. ^Vhen the beetles were then removed 

 to air, the abdomens began coloring almiost at once. Within five min- 

 utes the blue color had extended and deepened so that the abdomen Avas 

 as blue as when first placed in the carbon dioxide. The coloration be- 

 gan most noticeably at the sides near the spiracles. As is well known, 

 Indigo White becomes blue Indigo Carmine as soon as oxj^gen reaches 

 it. The experiment therefore, afforded visible proof that oxygen passed 

 to all internal parts of the abdomen without the aid of respiratory move- 

 ments — the heart was not beating even, when the blue color was re- 

 appearing. 



Methylene Blue could be used in the same way, but the reduced, white 

 compound of this dye does not reoxidize so rapidly as the reduced 

 Indigo Carmine. 



INFLUENCE OF CARBON DISULPHIDE UPON THE LUMINOSITY OF THE PHOTO- 

 GENIC ORGANS OF PHOTURUS PENNSYLVANICA LARVAE.* 



The larva of P. pennsi/lvanica has a pair of Photogenic organs on 

 the ventral outer portions of the eighth abdominal segment. When 

 pure carbon dioxide was rapidly admitted to living specimens of the 

 larvae in a respiration container above mercury, the phosphorescent 

 light — even when in full glow — would quickly die out. When air or 

 oxygen was admitted again, the glow would reappear. Also, if the 

 organs were cut out separately when the insect was causing them to 

 glow brightly, the light would continue for some time. 



Organs cut out in this way and placed at once on wet blotting paper 

 would give off light in a dark room for thirty minutes or more. When 

 these organs on wet paper were placed in a respiration container above 

 mercury, the light would cease in pure carbon dioxide just as in case 

 of the living insects. Upon admitting air the glow reappeared again 



♦Specimens were obtained from Mr. C. S. Brimley, Raleigh, N. C. 



