104 Gerald F. Hill: 



experiments, during which the temperature ranged from 44° F. to 

 68°F., the first pupa developed into a young ** tick " on the sixth 

 day and the last on the eleventh day. In the other experiment, 

 during which the temperature varied from 34T. to 86°F., the first 

 ** tick " did not appear until the twenty-second day and the last 

 not until the thirty-fourth day. 



The experiment which gave the lowest percentage of emergences 

 was one in which the pupae were placed on dry sand and incubated 

 at a temperature of 96.8°F. Under these conditions 4 % of the 

 pupae developed into Louse-flies, namely two of a total of fifty. 

 Both emergences took place during the first day. 



Under the following five sets of conditions the development of the 

 pupa was absolutely inhibited, namely, (1) pupae on moist sand in 

 incubator at 96.8°F., (2) on sand on lawn at temperatures vary- 

 ing from 34°F. to 86°F., (3) on sand on lawn at temperatures vary- 

 ing from 47°F. to 84°F., (4) on moist sand in cellar at tempera- 

 tures varying from 50°F. to 59°F., and (5) on dry earth in cellar at 

 temperatures varying from 50°F. to 59°F. 



General Summary and Discussion. 



As is well known, the members of the family Hippoboscidae, to 

 Avhich the Sheep Louse— fly belongs, are all parasitic in the adult 

 stage upon birds or mammals, and as in the other families of the 

 Sub-order Pupipara, the larva is retained in the body of the female 

 until it is nearly ready to transform into the pupal stage. 



Unlike the true tick, which leaves the host to oviposit, the Sheep 

 Louse-fly, or '' sheep-tick," spends its whole life upon the host. 

 The nearly fully developed larva is extruded into the wool, where 

 it transforms, about twelve hours later, into a pupa, from which it 

 is, however, externally indistinguishable except in hardness and 

 colour. This pupa, or more correctly puparium, since the pupa 

 is enclosed within the larval skin, is securely attached to the fleece 

 ^yy a glutinous substance which is extruded by the female with the 

 nearly fully developed larva. 



The incubation period of the pupa varies according to tempera- 

 ture. On sheep kept here in a stall in winter, when the tempera- 

 ture varied from 43°F. to 47°F., the period was found to be from 

 twenty-two to twenty-four days. In summer, when the temperature 

 varied from 47°F. to 72°F., the period on stalled sheep was found 

 to be nineteen to twenty-one days. 



