514 
in length from - r s j of an inch. Small examples are found where 
the temperature has been low or excessively hot and somewhat dry. 
Large examples invariably occur in fermented materials, more 
especially so in stable manure. 
“ in stable middens the pupae occur chiefly at the sides or at the 
top of the wall or framework of the receptacle, where the temperature 
is lowest. In such situations they were often found packed together 
in large masses numbering many hundreds (see figs. 6, 7). The flies 
emerge from the pupae, under the most favourable conditions, in five 
to seven days. In ashpits they occur in the positions already 
indicated, and if similar conditions as to heat prevail, the period is 
approximately the same ; but in all cases where heat is not produced 
by fermentation, the pupal stage may last from 14 to 28 days, or even 
considerably more. 
4th Stage. I he perfect fly escapes from the pupa by breaking 
away the anterior end ; this it accomplishes by inflating the frontal 
sac ’ wb * c h is situate in the front portion of the head, between the 
eyes. By the inflation of this sac, the fly is also enabled to force its 
Ua ' though the manure or ashes into the open air. When once it 
las liberated itself, the wings develop, and when the integument has 
SU Ciently hardened the fly takes to wing. Pairing then takes place, 
eggs are laid, and another generation is started. The whole cycle 
om egg to perfect insect occupies, under the most favourable 
, , ltlCnS ’ ^ rom ten to fourteen days; but in low temperatures the 
e ,, C ^ Ce may ex ’t en d to several weeks. No growth takes place 
after the wings are developed. 
j ]r at ^e flies migrate from their breeding places to man's 
beino- ^ CJU ' te ev *^ ent . even to the layman, the primary object 
found 1 1 PPar f nt , y t0 ° btain f °° d and sheIter Many flies are als0 
they LJT P dmlng Winter and earlv spring, though whether 
to ilCIif Z m T:« Iely ” this has not yef been ab,e 
remain over tl lf » 1 X probable > however, that some pupae* may 
the breedino- places" h -'"k ^ ^ f ° 1Iowin ^ sprin g- NoW that 
easy matter t * a ' C Cen dlsc ° vere d, it will be a comparatively 
*> matter to ascertain if this is the case or not. 
b,lt this u 11 f ° r ‘unate^T*dfrl not°ptoduee U | se ^? y ■ was found doting the 
not produce a fly i n the following year. 
winter month?, 
