BLOOD-SUCKING NEMATOCERA : CHIRONOMID^ 121 



3rd, 4th, and 5th longitudinal veins may all be forked. The 

 family is a very large one and is represented in all parts of 

 the world and at all altitudes, the commoner species occurring 

 in dancing swarms near water. The larvze are mostly aquatic, 

 but some live in the sap that flows from diseased trees, and 

 in decomposing vegetation. Only the females of certain 

 species of the subfamily Ceratopogonince suck blood. 



The eggs of Chiro7tomus are laid in strings or lumps 

 of transparent jelly-like mucus, in stagnant water, and the 

 aquatic larvae — which, from the hsemoglobin contained (in 

 solution) in the blood of many species, are often red, and 

 hence are known as " blood-worms " — may come to the 

 notice of the medical officer when they are found, as they 

 often are, in the settling-tanks of waterworks, or in water 

 stored for domestic use. The larva (Fig. 27), which resembles 



eyes 

 anr 



saJiv.gl jj//^ 



anrrlegs fioshUjs 



Fig. 27.— Head and after end of Chiroiwmus Larva. 



a small river-worm, may sometimes be seen writhing through 

 the water, but it often lives in temporary tubes formed of 

 mud and fine debris entangled in slime secreted by the 

 large salivary glands (Fig. 22). It is composed of a head and 

 twelve segments ; on the head there are two pairs of small 

 eye-spots, a pair of antennse, and mouth-parts formed for 

 biting ; on the first and last segments of the body there are 

 two short legs ending in a ring of booklets ; on the ventral 

 surface of the penultimate segment there are four longish 

 filaments, and at the end of the last segment there are four 

 shorter filaments ; these act as true gills, the tracheal air- 

 system being not functionally developed. Different species 

 of Chironomus larvae have different habits ; some common 

 species are found in ditches, ponds, and water-butts ; other 

 species live at the bottom of deep lakes, or even at the 

 bottom of the sea. The pupa of Chironomus has a general 

 resemblance to that of Culex, but breathes by a pair of thick 



