230 MOSQUITOES OF NORTH AMERICA 



that the larva can turn it completely around with the utmost ease; it feeds 

 habitually with the under side of the head towards the surface of the water 

 whereas the upper side of the body is towards the surface. In this customary 

 feeding position, the mouth-parts are working violently ; the long fringes of the 

 mouth-parts cause a constant current towards the mouth and the particles float- 

 ing on the surface of the water in the neighborhood thus gradually converge to 

 the mouth opening and enter the alimentary canal. The spores of algge, bits of 

 dust, minute sticks, bits of cast larval skins, everything in fact which floats, 

 follow this course, and, watching the larva under the microscope, they can plainly 

 be seen to pass through the head into the thorax until they are obscured by the 

 opaque color of the larva's back. This is the common method of feeding when 

 full grown; however, the larva will descend in the shallow water and mouth 

 over the slime on pebbles at the bottom. Occasionally a fragment, too large to be 

 swallowed with ease, clogs the mouth. Sometimes it enters the mouth and sticks. 

 In such cases the head of the larva revolves with lightning-like rapidity until 

 the top of the head is upwards, and the fragment is nearly always disgorged, 

 although sometimes it is swallowed with an evident effort. 



As indicated, the larva feeds upon everything that floats. It is especially often 

 found in stagnant water on which there is more or less of an algal scum ; there- 

 fore a very frequent food consists of algal spores, and the color of the larva is 

 influenced more or less by the character of the food, green algae making it green. 

 Daniels, in his African investigations found that the contents of the intestines 

 of the larvae are mainly vegetable matter, in some cases entirely so. " Occasion- 

 ally limbs of minute insects or crustaceans are found as well as scales of mos- 

 quitoes or other insects. On watching them feeding, it is seen that all minute 

 particles are drawn to the mouth, but many of them are rejected. This rejection 

 is somewhat arbitrary, as a particle at first rejected is often subsequently swal- 

 lowed. Amongst the bodies seen to be swallowed I have seen living minute crus- 

 taceans and young larvse, both of anopheles and culices, but, as a rule, living 

 animal bodies either escape or are rejected." Christophers and Stephens state 

 that in their observations in Sierra Leone the food of the Anopheles larvae seemed 

 to be an unicellular organism. James and Liston state that the food of Anoph- 

 eles larvae consists chiefly of minute water animals which abound among algae 

 and other water plants. They believe that the larvae can not subsist upon vege- 

 table diet alone and that the duration of the larval stage depends chiefly upon the 

 supply of animal food. When this is small in proportion to the number of larvae, 

 they state, the stronger larvae kill and eat the weaker. The cause for the dis- 

 crepancies in these observations undoubtedly lies, at least in part, in the fact that 

 different species were under observation. Thus we have found that the tree-hole 

 inhabiting larvae of our Gododiazesis harberi are very largely predaccous and 

 prey upon other culicid larvae associated with them. The species inhabiting 

 bromeliads have similar habits, as has been recorded for Anopheles cruzii by 

 Peryassii. 



