THE VICTORIAN NATURALIST. 97 



be one of the uses of the secretion, for, from various observations 

 made at different times, the centipede is more than usually 

 luminous when attacked. One case {Nahcre, January, 1902 (32)) 

 was observed in the summer of 1897 in England. The centipede 

 had evidently been attacked by about a dozen ants, and was 

 seen ridding itself of its enemies by excreting a luminous material 

 over them. 



Now we come to the glow-worms and fire-fiies, which are much 

 brighter than any of the forms with which we have been dealing. 

 The glow-worms (8) are so called on account of the worm-like 

 form of the female, which is wingless and crawls about on the 

 ground. The male is winged and has the luminous organs more 

 restricted in area, and in consequence its light is not so bright. 

 They are situated at the hinder end of the abdomen, at the very 

 ends of the minute tracheal or air tubes, which branch in all 

 directions over the body of the insect. Experiments show that 

 the light is under tiie control of the nervous system, which 

 regulates tiie supply of air in the tracheal tubes. 



The fire-flies are more numerous in warmer climates, and are 

 found nearly everywhere in the tropics. In this case also (31) it 

 is the male which flies about, and is much more often found. In 

 a great number of countries they are used for decorating and 

 lighting purposes. Some friends who travelled in Japan a year 

 or two ago told me that fire-flies there were sold in little cages, 

 one, two, or three in a cage, according to the price paid. To 

 give some idea of the light emitted by these beetles, they said 

 that travelling once at night the second class railway carriages 

 were not provided with lamps. The Japanese passengers, how- 

 ever, carried two or three fire-flies each, and the light given by 

 these was quite sufficient to enable my friends to see the faces of 

 all the people in the carriage. 



One of the best known of the fire-flies is the so-called Mexican 

 fire-fly, Pyrophorus, which is supposed to give a light quite 

 strong enough to read by, from two oval patches on the thorax. 

 Darwin describes immense numbers of these insects seen in a 

 few days' journey from Rio Janeiro. Another South American 

 beetle is Phengodes, which shows the curious larva-like form of 

 the female with the luminous organs arranged at the sides of the 

 body, one in each segment of the abdomen. The light in many 

 cases is different in colour in the different species — green in the 

 glow-worm and some fire-flies, blue in the Italian fire-fly, and 

 purple in the lantern-fly, Fulgora, of America and China, which 

 has luminous organs at the tips of its long proboscis. 



One more instance of a luminous insect comes from New 

 Zealand, this time belonging to the Diptera, or flies. The life- 

 history of this was first observed by Mr. Hudson (19), of 

 Wellington, and was complete as to facts, though he stated that 



