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Outline of Life-liistory 



Peculiari- 

 ties of 

 t'resli- 

 hatched 

 larva. 



Some com- 

 mon species 

 of Chiro- 

 nomus. 



the form of a double cord, which traverses the egg-mass 

 and projects beyond it at one end (fig. ii6). During the 

 process of oviposition the female is not easily induced to 

 break off'; if she is forcibly removed from the surface of 

 the water, she sometimes flies a short distance with the 

 egg-mass protruding, which disproves the statement 

 formerly accepted, that she begins by making fast the 

 end of the cord ^ The eggs are almost transparent, and 

 can be studied microscopically while still alive. They 

 hatch out in three to six days. 



When fresh-hatched, the Chironomus-larva is some- 

 what less peculiar than after its first moult ; it has at first 

 no red colour, and no blood-gills on the last segment but 

 one ; the brain is not retracted into the prothorax, but 

 enclosed in the head, and the nerve-cord is visibly'' 

 double throughout its whole length. This is an ex- 

 ample of what zoologists call Recapitulation, the earlier 

 stage retaining more of what we take to be the primitive 

 structure. 



There are many species of Chironomus, and it is 

 remarkable that while the flies are very similar, the 

 larvae are sometimes notably different. Two forms 

 occur frequently. In one group of species the larva often 

 has four long tubules (blood-gills) on the under- side of 

 the body at the tail-end (fig. i) ; the pupa bears bunches 

 of long filaments (tracheal gills) behind the head, and 

 has a fringed tail-plate (Plate, figs. 5, 6). To this group 

 belong the comparatively large red larvae, which are 

 called blood-wormfi. In a second group the larval tubules 

 are absent ; the pupa has a pair of short and simple 

 trumpets in place of the bunches of filaments (fig. 7) ; the 

 tail-plate is not fringed, but merely furnished with two 

 bunches of short bristles ^. 



Most of the larvae of the first group burrow; the larvae 



' Eitter. 1890, p. 411. - Meinert, 1886, p. 75. 



