8i 



brushes and the currents they produce on the sur- 

 face of the water. Note the rotation of the head 

 so that, whilst feeding, the ventral surface of the 

 head is uppermost. 



3. The Food of Larvae. — Tear a larva to pieces 

 with a needle and remove a small portion of the 

 dark central mass of food material filling the 

 straight alimentary canal. Place in a drop of 

 clean water and crush under a coverglass. Note 

 what organisms form the chief bulk of the food. 

 Note the presence of sand grains — unicellular 

 plants and animals — short lengthsof alga, diatoms, 

 etc. Also bacilli. 



Determine the common foods of several species 

 of Anophelines. 



4. Desiccation of Larvae. — Celli and Casa- 

 GRANDi have found that Anopheline larvae can only 

 resist desiccation at 20° C. for two days, at 35° C. 

 for one day, and 40° C. for two minutes only. 

 Larvae of Anophelines stranded on moist mud will 

 live as long as four days, but in the tropics as 

 soon as the mud loses its glistening surface they 

 die. 



Culiciyie Larvae. — The larvae of the Culicidae, 

 with the exception of those of Anophelines and 

 possibly some other genera, are superficially much 

 alike. The conspicuous hairs and spines, and 

 even the complicated terminal segment, are very 

 similar in the different genera. There are, how- 

 ever, marked differences in some features on closer 

 examination. These differences are mainly to be 

 found in the syphon tube, the antennae, and 

 mental plate, but to a less extent in other 

 structures. 



