310 



— Apical abdominal segment not as above, or the internal portion of 



head is without arched upper plate, and the longitudinal cephalic 



rods and other cephalic parts meet at right angles 9 



9. Apical abdominal segment Avithout projecting processes, the spira- 

 cles very small; species internal parasites of spiders 



Cyrtidae (p. 368) . 



— Apical abdominal segment frequently with projecting processes, the 



spiracles large; species living in water, mud, earth, or decaying 

 vegetable matter i Empididae (p. 400). 



I DOLICHOPODIDAE (p. 403). 



10. Posterior spiracles situated upon antepenultimate segment ; ab- 



dominal segments 1-6 subdivided, the body apparently consisting 

 of 20 segments exclusive of the head 11 



— Posterior spiracles situated upon penultimate segment; abdominal 



segments simple, the body apparently consisting of 11 or 12 seg- 

 ments exclusive of the head 12 



11. Posterior dorsal internal extension of head spatulate at apex; ven- 



tral posterior projections in the form of 2 short chitinized rods. . 

 Therevidae (p. 396). 



— Posterior dorsal internal extension of head not spatulate at apex; 



ventral posterior projections absent Scenopinidae (p. 398). 



12. Penultimate abdominal segment longer than ultimate, with a deep 



transverse depression near its apex giving it the appearance of 

 2 distinct segments ; ultimate segment terminating in a sharp 

 ridge with a median sharp point, on either side of which dorsally 

 and ventrally are situated 4 very closely approximated hairs simi- 

 lar to those in Asilidae Mydaidae (p. 370). 



— Penultimate abdominal segment shorter than ultimate, or if longer, 



then without a deep transverse depression ; apical segment not as 

 above, the hairs not closely approximated 13 



13. Thoracic segments each with 2 long hairs, one on each side on ven- 



tro-lateral margin ; apical segment with 6 or 8 long hairs ; head 

 well developed, forwardly protruded, and more or less cone- 

 shaped when viewed from above, appearing flattened when viewed 

 from the side ; penultimate segment usualh' shorter than ultimate 

 or not much longer; body straight in life Asilidae (p. 373). 



— Thoracic segments without hairs, or if these are present they are 



very weak ; apical segment without distinguishable hairs ; head 

 not much protruded, directed downward, not cone-shaped, with 

 a dorsal protuberance when viewed from the side; penultimate 

 segment distinctly longer than ultimate ; body usually curved in 

 a half circle in life BoMBVLnDAE (p. 389). 



PUPAE 



1. Pupa enclosed within the last larval skin. . Stratiomyiidae (p. 315). 



— Pupa free 2 



