1886. ] Entomology. 809 
dorsal lamps on the prothorax near its margin, and a large ven- 
tral lamp on its abdomen. The organs are developments of the 
hypodermis, are largest in the male, and the abdominal one is so 
thin and transparent that we can see the ventral nerve-cord 
through it. Branches of the trachea end in the luminous cells; 
they are bordered by such cells, but no end-cell on the trachea 
could be made out. Internal to the luminous layer is a non- 
luminous layer, formed by tracheal branches and irregular cell- 
Masses, specially rich in urates. Though the light is usually 
nocturnal, yet if the animal is disturbed by day it will shine less 
brilliantly. Even a sleeping cucuyo will show in a dark cham- 
ber a mild light from the dorsal organs; the light of the abdo- 
minal organ cannot then be seen, as the insect rests with its 
abdomen doubled up against its sternum. If at such time we 
awake it, the breathing begins, whereon the light appears in its 
Splendor. There are two kinds, or rather two degrees, of lumin- 
Osity, one soft, the other bright, which may be termed respec- 
tively the cell-light and the tracheal-light. One may change into 
the other just as the dull glare of a smith’s coals will on the 
action of the bellows develop into a bright flame. In the abdo- 
men the lateral parts begin earliest to shine, and retain their 
luminosity the longest, because they occupy the place nearest 
the lateral tracheal trunks. During flight the abdominal organ 
iS In Constant activity (here differing from Lampyridz in which 
the light is intermittent), In a dark room the light appears clear 
green, inclining to blue; in daylight it is yellowish. The spectrum 
analysis has not been satisfactorily effected; but the light 
seems to produce a spectrum wanting half the blue and deficient 
in the red. An extracted luminous organ will continue to give 
red light for some hours (for twenty-four hours if kept in. moist 
air), No light-nerves were found, and so far there was no evi- 
dence of the luminosity being under control of the will. It is 
Said that in Lampyridz the will and the nervous system control 
the light. In Cucuyo the abdominal light at least depends only 
On the respiratory center, which is in the metathoracic ganglionic 
mass. The expiration only of the abdomen is active, and the in- 
SPiration is the passive act of the abdominal muscles returning to 
their place of rest. On every such inspiration the air brought 
by the trachez causes the luminous organ to give its bright, 
Steady light. It is manifest that the light depends on a process 
of oxidation. All experiments, mechanical irritation, chemicals, or 
mild cell-light. Buta stream of atmospheric air, and especially 
