A4 THE BLowFuies or NortH AMERICA 
Occipital orbits wide, the intrapostocular cilia very distinct, 
greater ampulla often pilose or setose; lower calypter trun- 
eate posteriorly, slightly to considerably concave on the 
lateral margin, and on the. upper surface always pilose at 
base, as in Phormiini, to setose on the dise as in Chry- 
somyini (bare in Hemilucilia and Chloroprocta). Third 
instar larva with spiracular ‘‘button’’ not within closed 
peritreme which does not separate each slit-like aperture; 
cephaloskeleton not appearing divided ............... 
ee es eee oo etn ce SRR: eee ee Chrysomyinae, p. 95. 
9. Prosternum and propleuron setulose or pilose; vestiture of 
parafaciale not reaching lower eye margin; thorax without 
crinkly hair. Third-instar larva with closed, strongly 
sclerotized, peritreme .......... Calliphorinae, p. 202. 
Prosternum and propleuron bare; parafacials setose to lower 
eye margin; thorax with crinkly hair. Third instar larva 
with weakly sclerotized closed peritreme....Polleniinae, 
p. 340. 
