102 THE BLOWFLIES oF NortH AMERICA 
2. Second and third instars with spines on anal protuberance 
arranged in V-shaped group; dorsal spines on segments 
B-LO ve AEF AEE Uae 3 
Second and third instars with spines on anal protuberances 
not arranged in V-shaped group; dorsal spines absent on 
segments 8-10.00 Ny 0 EE a”, 
tA Chloroprocta fuscaamipennis (Macquart), p. 119 
3. Second and third instars with tracheal trunks leading from 
posterior spiracles not pigmented.................+.. 4 
Second and third instars with tracheal trunks leading from 
posterior spiracles pigmented, dark brown to black .... 
.... Callitroga americana (Cushing and Patton), p. 132 
4, Second instar with ratio of distance between inner tubercles 
on upper margin of posterior cavity and distance be- 
tween inner and median tubercles on each side approxi- 
mately 1.5:1.0. Third instar with accessory oral sclerite 
absentiiAveetes Callitroga macellaria (Fabricius), p. 144 
Second instar with ratio of distances between tubercles men- 
tioned above approximately 1.1:1.0. Third instar with ac- 
cessory oral sclerite* present. 22252. (02. 2 ee 
i a ay Rr Paralucilia wheelert (Hough), p. 155 
5. Second instar with dorsal spines present on posterior margin 
of segment 10. Third instar with larger tubercles on up- 
per margin of posterior cavity distinctly longer than one- 
half the width of one posterior spiracle;-dorsal spines 
present on posterior margin of segment 10 ............ 6 
Second instar with dorsal spines absent on posterior mar- 
gin of segment 10. Third instar with length of larger 
tubercles on upper margin of posterior cavity less than 
one-half the width of one posterior spiracle; dorsal spines 
absent on posterior margin of segment 10.............. 
TEES Oe they oe e582 Phormia regina (Meigen), p. 166 
6. Cephalic segment small, nearly bare, rounded, second seg- 
ment flattened, and with numerous marginal rows of 
minute spines which are longer toward margin........ 
1 2 7aO Apaulina avium (Shannon and Dobroseky), p. 188 
Cephalic segment as in Phormia, second segment not flat- 
tened, and without numerous rows of minute spines as 
deseribed 3..5,0-4's empavacdebvates. 9 ve sittia deve cieneee eae ee 
..Protophormia terrae-novae (Robineau-Desvoidy), p. 177 
