378 KATHARINE FOOT. 



glass in even a fraction of a drop of water, he cannot regain his 

 feet until the water dries and if the glass is not clean he adheres 

 to it and finally dies. 



After trying the usual method of keeping the lice on small 

 pieces of woollen or muslin cloth it occurred to me that a large 

 number of short pieces (about 8 mm.) of soft, coarse thread 

 would have many advantages. First they would be much more 

 sanitary for they can be changed every day if necessary without 

 disturbing the lice at all. When lice are on a small piece of 

 cloth, the cloth becomes filthy in a few days and it is exceedingly 

 difficult to remove the lice to fresh pieces. Further the thread 

 avoids all the difficulties encountered in transferring and counting 

 the lice. They cling to a thread with great tenacity; therefore 

 single lice can be carried on a thread any distance with perfect 

 safety. They deposit their eggs on the thread and therefore the 

 eggs deposited each day can be conveniently collected and iso- 

 lated. Using these threads made it a simple matter to record the 

 following life history of a single pair of lice. The pair was 

 hatched from eggs deposited in the laboratory and had their 

 third (final) moult August 19. They were seen mating August 

 22. The next day 4 eggs were deposited and thereafter 4, 5 or 6 

 were deposited daily until the female died. 



RECORD FL. D. 



1918. Eggs. Hatched. 



Aug. (Mated Aug. 22) 



23 Mated 4 



24 3 



25 5 



26 4 



21 ... 4 



28 5 



29 5 



30 4 



31 5 



Sept. 



1 5 



2 Hatched the loth day 6 i 



3 5 3 



4 54 



5 (Mated) 5 3 



6 (Male dead each daily deposition of eggs kept separate 



from death of male) 5 7 



7 5 3 



