500 THE INSECT WOBLD. 



soft, which very soon hardens, and becomes of a bright tawny 

 colour ; it is called the pseudo-nymph (Fig. 545). It goes through 

 the winter in this state. In the spring comes forth a third larva 

 (Fig. 546), resembling the second. This one does not eat, and 

 moults after a time. It very soon changes into an ordinary 

 pupa (Fig. 547), of a yellowish- white, from which comes forth the 

 adult Sitaris, which lives only a few days, to ensure the propaga- 

 tion of its species, as is observed in the case of the Ephemerte. 

 The larvae of the Sitaris had for a long time been remarked 

 clinging on to the hairs of the Anthophoras; but they were always 

 taken for Acari, and they had been described as such. 



The Lampyridae have the elytra weak and soft, like the insects 

 of the preceding tribe. In their perfect state they frequent 

 flowers. The larvae are carnivorous, attacking other insects or 

 worms. It is to this group that the Lampyris noctiluca, or glow- 

 worm, which one sees shining during summer nights on grass 

 and bushes, belongs. It has the power of making this natural 

 torch shine or disappear at will, which is, by-the-bye, a property 

 common to all phosphorescent animals. 



The luminous properties with which these insects are endowed 

 have for their object to reveal their presence to the opposite sex, 

 for the females alone possess these properties. In the same way 

 as sounds or odours exhaling from some insects attract the one 

 towards the other sex, so with the Lampyris a phosphorescent 

 light shows the females to the males. The seat of the phos- 

 phorescent substance varies according to the species. It exists 

 generally under the three last rings of the abdomen, and the light 

 is produced by the slow combustion of a peculiar secretion. It 

 has been stated that it is evolved quickly when the animal con- 

 tracts its muscles, either spontaneously or under the influence of 

 artificial excitement. Some chemical experiments have been made 

 to ascertain the nature or the composition of the humour which 

 produces this strange effect ; but, up to this moment, they have 

 only enabled us to discover that the luminous action is more 

 powerful in oxygen, and wanting in inert gases. In the most 

 common species, the Lampyris noctiluca, or Glow-worm, the phos- 

 phorescence is of a greenish tint ; it assumes at certain moments 

 the brightness of white-hot coal. 



