14 Outline of Life-history 



The pupa has a tail-fin composed of thirty to forty long 

 setae, and the abdominal segments are laterally expanded. 

 On the second abdominal segment are paired postero- 

 lateral transparent appendages of small size, enclosing- 

 minute blood- spaces. There are two conical prominences, 

 each bearing a long seta, on the vertex of the head. 

 Corresponding structures were not found in the ^y. 

 The tracheal gill divides into three primary branches as 

 usual. The secondary branches are comparatively few ; 

 each encloses a number of tracheae, which pass to the 

 ultimate branches. 



In the legs of the fly the variety of colouration, noted 

 by Zetterstedt, was very apparent, though all the speci- 

 mens were taken at the same time and place (Meanwood 

 Beck, June, 1899). 

 chirono- Lyonet met with a tube-dwelling larva, of which an 



Sadii?s)* "' account is given in his Anafomie et JSIetamorphoses de 

 nvon%iro- difere7ifes especes d'Insectes, a posthumous work edited 

 "^''^' by De Haan. He speaks of the tube as formed of silk and 



a sort of moss, plentiful in ditches ; it is open at both 

 ends, enlarged in the middle, and sufficiently transparent 

 to allow the movements of the larva to be watched. 

 Unlike most other tubes secreted or built up by insect- 

 larvae, the one in question is so flexible as to follow the 

 bendings of the body when this is energetically contorted. 

 He describes the method of feeding of the larva, which 

 seizes the moss between its mandibles and fore-legs, and 

 drags it into the tube, and its way of moving about, by 

 grasping with the mandibles and fore-legs alternately. 

 If the tube becomes lodged so as to be immovable, the 

 larva quits it and makes another. When free, it swims with 

 a looping action. The full-fed larva pupates in its tube. 

 Beyond this point the description does not go. as Lyonet 

 had mislaid his notes. He figures the tube, the larva, the 

 pupa, and the male and female fly. De Haan identifies 



