Insects ami Parasitic Diseases. 85 



The history of another ,experiment similar to the above is 

 irecorded on p. 82, Experiment No. 5. In this experiment only five 



** ticks " could be traced at the end of the thirty-second day 



(February 24th), during which period the two surviving females 

 •each extruded two pupae. On February 24th these five "ticks" 



were liberated on a lamb previously freed of " ticks." On February 

 ■26th and two subsequent days only one female and two or three 



males could be accounted for. 



Three other similar experiments were commenced in February 

 .and March, but as satisfactory i-esults could not be obtained they 



were abandoned a few weeks later. 



4. To determine the number of pupae extruded by an individual 

 female and the time elapsing between each extrusion. 



Attempts to determine the length of life of the female Louse-fly 

 having failed, it is obvious that the number of pupae extruded 

 by an individual female could not be determined. The results of 

 two experiments, however, may be referred to again as indicating 

 the periods elapsing between extrusion of the first and subsequent 

 pupae. 



In Experiment No. 4 three young " ticks " which were liberated 

 ■on a lamb in mid-summer (January 12th) each extruded the first 

 pupa about the twenty-first day, the second pupa about the thirty- 

 first day, and the third pupa (in the case of two '* ticks ") about the 

 thirty-ninth day. In Experiment No. 5, two young " ticks " each 

 extruded the first pupa about the tAventy-third day, and the second 

 pupa about the thirty-second day. 



Thus the period which elapsed betAveen the extrusion of each pupa 

 was about nine days (9.14 days). These periods are reckoned from 

 the date of finding of the pupa, Avhich in some cases may have been 

 a day or more after their extrusion ; they should be regarded 

 therefore as approximate only. Swingle's investigations in 

 America (1913, pp. 19 and 20), showed that the average rate of 

 pupa laying was one about every eight days (7.89 days in one 

 experiment and 7.99 days in another). 



'5. To determine the period of viability of the Sheep Louse-fly when 

 removed from the host, (a) unfed flies under one day old, 



(b) flies from three to seven days old which had fed, 



(c) adult flies. 



A series of experiments with forty-six groups of Sheep Louse-flies 

 skept under thirteen different sets of conditions was commenced in 



