THE PHOTIC REACTIONS OF SARCOPHAGID FLIES 221 



but as the moisture is eliminated and the larvae become full 

 grown they are left in a rather precarious position. The remnants 

 of the fish or other dead body can then be easily dislodged by 

 the winds or other mechanical means, and the larvae are then 

 exposed to the ravages of birds, as has already been stated. The 

 heat of the sun also would then result disastrously to them. The 

 importance of moisture in the economy of the flesh-flies has been 

 pointed out on several occasions (Herms, '07, pp. 49, 67, and 75). 

 It must be evident that the phototactic response of these larvae 

 is highly adaptive to the situation. By this means the larvae find 

 places of shelter from light, away from the desiccating influence 

 of the sun, removed from preying birds and other disturbing 

 elements. This response, coupled with their strong thigmotatic 

 reaction (Herms, '07, p. 82) as seen in burrowing, affords a natural 

 and almost complete protection for the individual and consequently 

 for the species. 



V. GENERAL SUMMARY 



1. The egg-stage of Lucilia caesar and Calliphora vomitoria 

 covers a period of from 8 to 48 hours; the feeding period from 2 

 to 7 days for the former species, and from 3 to 9 days for the latter; 

 the prepupal period usually from 2 to 7 days (extreme 59 days) ; 

 the pupal period usually from 8 to 17 days (extreme 34 days). 

 The most variable in length is the prepupal period. Constancy 

 in environmental conditions results in uniformity. The shortest 

 time observed between emergence from the pupa and egg deposi- 

 tion was 9 days for Lucilia caesar and 12 days, for Calliphora 

 vomitoria. 



2. The usual length of life of an imago flesh-fly is about 30 

 days, regardless of sex. The longest recorded life of a single adult 

 individual was 63 days. 



3. A positive reaction to kerosene lamplight, acetylene gas- 

 light, monochromatic light, and solar spectrum was demonstrated 

 on the part of the aggregated feeding larvae of Lucilia caesar dur- 

 ing a limited part of this period, causing the larvae to leave their 

 food (as far as 16 cm.). Under the solar spectrum the feeding 

 larvae are positive to the red end, collecting especially in the yellow- 



