CLASS INSECTS. 423 



the folding or clapper of a door. A pair may generally be 

 seen on the lateral and upper parts of each ring ; but they 

 are often absent in the last two segments of the thorax. 



With regard to the mechanism by which the air is renewed 

 in the interior of this respiratory apparatus, it would seem 

 to consist generally in the movements of contraction and 

 dilatation of the abdomen. Thus, as we have already said 

 elsewhere, the respiration is very active in these animals. 

 They consume a considerable quantity of air, compared with 

 their bulk, and speedily asphyxiate when deprived of oxygen ; 

 but when they are in this condition of apparent death, they 

 can continue so for a great length of time without losing the 

 faculty of returning to life. 



528. Most insects produce but very little heat ; but 

 some of these animals disengage, under certain circumstances, 

 a sufficiency notably to raise their temperature. Bees offer 

 an example of this, especially when they are much agitated 

 in their hive ; and it is to be observed that the respiration 

 becomes then very active. 



529. Another and a more remarkable phenomenon, and 

 of which the cause is still unknown, is the production of 

 light observed in some insects. The lampyris or glow-ivorm 

 is an example of this, well known to all who frequent the 

 fields : the male (Fig. 444), which has wings, is but little 

 luminous ; the female (Fig. 445), which has no wings, and 

 which is often found during the warm nights of summer on 

 the thickets, spreads around a very lively phosphorescent 

 light. In another species of lampyris inhabiting Italy, the 

 individuals of both sexes are at the same time winged and 

 luminous ; but this singular property is especially remarkable 

 in certain taupins inhabiting the hot regions of America, and 

 which produce, whilst they vault in the obscurity, a natural 

 illumination of the happiest effect; the women frequently 

 place them in their hair as ornaments, and it is asserted that 

 the Indians make use of them to point out the way during 

 the night. In one lampyris, the light comes from certain 

 spots situated over the two or three last rings of the abdo- 

 men ; whilst in the taupins it comes from analogous spots 

 over the prothorax or corslet. It appears that the insect can 

 vary at will the intensity of the phosphoric light, and that it 

 is connected with the action of the oxygen upon a fatty 

 matter secreted by the phosphorescent organs. 



530. The sexes are distinct in these animals, and there 



