GNATS 25 



normal food, and why they should seize the opportunity of 

 sucking blood is a mystery. 



Chironomus. The eggs of chironomus are laid in gelatinous 

 rope-like masses about f inch long, each of which contains a 

 large number of them. Their arrangement differs in the various 

 species, but in those which frequent flowing water the mass is 

 attached by a tough thread to some fixed object and is then 

 secured against the currents. The eggs are elliptical in outline, 

 and so transparent that the formation of the embryo within 



FlG. 14. A, spawn of chironomus : the mass is divided into sections so as to show 

 both sides ; B, twisted fibres which traverse the spawn-rope. (After Miall.) 



can be watched through the microscope. The larvae hatch in 

 under a week from the time of egg deposition. At first they 

 are of a transparent grey colour, and have a moderately large 

 head. After the first moult of the skin the head becomes relatively 

 smaller, the brain retreating into the prothorax, and a red tinge 

 pervades the whole body. The full-sized larva is about an inch 

 long and of a brilliant red colour, whence the popular name 

 of " blood-worm." The animal constructs a tube for itself by 

 glueing together particles of earth and vegetable matter, or of the 

 green slime that often covers the sides of vessels which have 

 long contained water. It moves up and down rhythmically 



