32 THE LIFE-STORY OF INSECTS [CH. 



imago and tlic larva. An adult may-fly is one of the 

 most delicate of insects ; the head has elaborate 

 compound eyes, but the feelers are very short, and 

 the jaws are reduced to such tiny vestiges that the 

 insect is unable to feed. Its aquatic larva is fairly 

 robust, with a large head which is provided with 

 well-developed jaws, as the larval and nymphal stages 

 extend over one or two years, and the insects browse 

 on water- weeds or devour creatures smaller and 

 weaker than themselves. They breathe dissolved air 

 by means of thread-like or plate-like gills traversed 

 by branching air-tubes, somewhat resembling those of 

 the demoiselle dragon-fly larva. But in the may-fly 

 larva, there is a series of these gills (fig. 9b) arranged 

 laterally in pairs on the abdominal segments, and 

 C. Bonier (1909) has recently given reasons, from the 

 position and muscular attachments of these organs, 

 for believing that they show a true correspondence 

 to (in technical phraseology are homologous with) 

 the thoracic legs. One feature in which the larva 

 often agrees with the imago is the possession on the 

 terminal abdominal segment of a pair of long jointed 

 cerci, and in many genera a median jointed tail- 

 process (see fig. 9) is also present, in some cases both 

 in the larva and the imago, in others in the larva 

 during its later stages only. The prolonged larval 

 life in may-flies often involves a large series of moults ; 

 Lubbock (1863) has enumerated twenty-one in the 



