42 



Though in many species the flashing of the male is so regular as 

 to suggest its being due to reflex rather than to voluntary action, yet 

 in the female the light appears to be more under the control of the 

 insect. In many species the light may be emitted after the death of 

 the insect, but in the case of males of the flashing species the light 

 is then constant instead of intermittent and less intense than in life. 

 While searching for the females of Litciola italica, I was several 

 times deceived by the constant faint light of a dead fire-fly caught in 

 a spider's web near the ground. 



Another group of beetles whose light-giving properties have 

 caused them to be very widely known — at any rate by name — are 

 the " Fire-flies " of Tropical America, Fi/rophonts. These must not 

 be confused with the " Fire-flies " of Italy and southern Europe, 

 which as I have said are really winged glow-worms allied to the 

 lightning-bugs of the United States. The fire-flies of tropical 

 America and the West Indies, the creatures that the local belles 

 wear in their hair and about their persons as a kind of living jewellery 

 known locally as Cucujos, belong to a very different famil}'^, the 

 Elateridje or Skip-jacks. They are considerably larger than the 

 glow-worms and their light organs are differently situated. The 

 most obvious are a pair of large yellowish spots on the thorax, one 

 near each of the posterior angles. If the beetle is examined alive, 

 these spots, the " eyes " as they are called, will at first be quite dull 

 and opaque ; but when the insect is handled they will soon be ob- 

 served to kindle, the glow increasing gradually in intensity till it 

 reaches its maximum. This light is only emitted by the fire-fly 

 when stimulated by some excitement, such as that caused by hand- 

 ling, and glows steadily so long as the excitement continues ; as this 

 wanes the light gradually dies away. 



When the insect is on the wing the light seen is net that emitted 

 from these eye-spots, but originates from another light organ at the 

 base of the abdomen. This organ is usually concealed between the 

 abdomen and the thorax, and is only exposed when the elytra are 

 open so that the abdomen can be bent back. The light is of a 

 redder or yellower colour than that emitted from the thoracic spots, 

 and is intermittent instead of continuous, the flashes being caused 

 by the light being alternately exhibited and concealed by slight 

 movements of the abdomen. The bionomic value of the light in 

 these insects is not at all understood, but it does not seem to have 

 any sexual function in this case. 



The larvte of these fire-flies are also luminous. They are of 

 typical elaterid form and live in rotten wood. In the young larvae 

 the light is emitted from the junction of the head with the bodj'', 

 but in the older larva it is emitted also from the junctions of the 

 segments all along the body. The eggs also are stated to be 

 luminous. 



Various beetles of other families have been recorded as luminous, 

 but all these records want confirmation, and some of them were 

 certainly only accidental. 



