go 



By keeping under observation a number of 

 nymphae, some will be seen to become less 

 inclined for active movement, and the abdominal 

 segments (tail) may be extended horizontally. 

 Soon after these changes the adult insect emerges 

 through a crack in the chitin of the back of the 

 thorax. The process as seen in Anopheles is very 

 fully described by Nuttall and Shipley.' 



Examination of Nymphae 



1. Note the effect of tapping the glass vessel 

 and the rapidity with which the nymphs regain 

 the surface. 



2. Observe that when first they appear the 

 nymphs are light in colour, but darken very con- 

 siderably later. 



3. Note that just before the hatching of 

 mosquitoes the nymph lies with the tail extended, 

 and that silvery marks may be seen, due to air 

 lying under the chitin. 



4. Observe the emergence of the imago. 

 Examine the nymphs of Anophelines, Culex, 



Taemorhynchus, etc., and observe that to the naked 

 eye they are very similar. 



1. Note that the nymphae of Anophelines lie 

 less vertically in the water than those of Culex. 



2. Observe that the nym.ph.sof Anophelines are 

 more elongated antero-posteriorly and compressed 

 laterally than those of Culex and Taeniorhynchus. 



3. Observe the very large nymphs of some 

 common species of Taeniorhynchus and the great 

 length of air tubes which are directed straight 

 forwards in a very characteristic manner. 



1. journal Hygiene, vol. 1, part H. 



