Mr. P. H. Gosse on the Insects of Jamaica. 201 



displays the light within redly and dimly, as if the whole thorax 

 were red-hot, particularly at the edges, immediately beneath the 

 tubercles. When left alone, the insect soon relapses into stillness, 

 and the tubercles soon fade into darkness, either total, or re- 

 deemed only by a spark scarcely perceptible. 



I had been familiar with this firefly for some weeks, and had 

 made the above observations on it, without being aware that it 

 possessed any other source of light than the thoracic tubercles. 

 I had indeed remarked that when flying at liberty the light 

 which it difi"used was of a rich ruddy glow, and yet these indivi- 

 dual insects, if captured and held in the hand, showed only green 

 light. I much wondered at this, but knew not how to account 

 for it, until a friend explained it, illustrating his remarks by ex- 

 periment. On the ventral surface^ when the abdomen is extended, 

 there is seen, between its first segment and the metathorax, an 

 oval transverse space, covered with thin membrane, which glows 

 with orange-coloured light ; totally concealed however when the 

 abdomen is relaxed, by the overlapping of the metathorax. When 

 the insect is placed on its back it throws itself into the air like 

 other Elaters ; but if it be made to repeat this many times it ap- 

 pears to become weary, and endeavours to raise itself by bending 

 the head and the abdomen back, so as to rest on the extremities, 

 in hope to roll over. It is when thus recurved that the abdo- 

 minal light suddenly appears, the oval space being uncovered. 

 When held in the hand, the same efifect is produced by forcibly 

 bending back the abdomen with the fingers ; but this is not very 

 easy of accomplishment, on account of the resistance of the closed 

 elytra ; but if these be held open with one hand and the abdo- 

 men recurved with the other, it is readily shown. As the open 

 space, then, can be exposed only when the elytra are expanded, 

 the reason is manifest why the red light is never displayed by 

 the insect when walking or resting : the green thoracic light on 

 the other hand may be displayed at any time ; it is however very 

 rarely shown during flight. On one occasion two or three fire- 

 flies, having entered the sitting-room in the evening, gave out the 

 red light most brilliantly as they flew round near the ceiling, the 

 spectators being beneath them ; one of these, being alarmed by 

 my eff'orts to capture it, gave out the thoracic light also very 

 brightly ; and the mingling of the green and red light in the 

 evolutions of flight produced an efiect indescribably beautiful. 



That the thoracic light is subject to the will of the insect is 

 indubitable ; but whether the same can be predicated of the ab- 

 dominal light I am not assured. During flight it is every second 

 intermitted, as far as the observer can detect ; but its appearance 

 or disappearance may depend upon whether the dorsal or ventral 

 surface is presented to the eye. This is when, soon after dark, 



