1969] 
Thompson — Microdontine Flies 
75 
hood, and connected posteriorly by membrane to dorsal infolded sur- 
face of penis sheath; cerci elongate. 
Type-species: Paragodon paragoides , new species 
Paragodon forms the plesiomorphic (primitive) sister group to the 
rest of the Microdontinae. It is the only known microdontine fly 
with a simple ejaculatory apodeme and sac. All other Microdontinae 
have an apical triangularly flared portion to the ejaculatory apodeme 
which fits into a. strongly sclerotized cup-shaped sac (Fig. 8). The 
other primitive (plesiomorphic) characters which Paragodon displays 
are: i) short antennae; 2) underdeveloped and bare metasterna; 
3) lack of basal setal patches on the femora; 4) lack of a spurious 
vein; 5) lack of an appendix on the third vein (R4 + 5); 6) pres- 
ence of a double sustentacular apodeme; 7) single, free ejaculatory 
process. The lack of cheeks on the head and the reduced thoracic 
pile are specialized (apomorphic) conditions. The isolated phylogen- 
etic position of Paragodon suggests a number of interesting questions. 
What will the larvae be like? Will they be found in ants nests 
like all other microdontine flies? And could Paragodon possibly be 
the adults of Wheeler’s N 0 thornier odon^ 
Since Paragodon appears to be the most primitive microdontine fly 
known, a general review of the characteristics and position of the 
subfamily seems in order. 
Subfamily Microdontinae 
A small (350+ species) group of diverse syrphid flies. 
Adults: Head: Face simple except slightly produced on the lower 
part in Microdon (Rhopalosyrphus) , pilose; facial grooves (anterior 
tentorial pits) reduced to pits; eyes dichoptic in both sexes; antennae 
usually long, longer than one-half as long as face except shorter in 
Paragodon and Paramicrodon , with first segment usually longer than 
broad except shorter in Paramicrodon delicatula Hull; aristae bare. 
Thorax: Humeri always pilose, proanepisterna bare, anterior 
mesoanepisterna pilose except bare in Microdon (Cerioimicrodon) , 
scutellum without ventral hair fringe; plumula not differentiated 
from subalar; postmetacoxal bridge always present and complete. 
Legs: femora and usually tibiae with cicatrices. Wings: with first 
posterior cell (R5) closed and usually obtuse, with apical crossvein 
(upper turned portion of Mi +2) recurrent or straight except di- 
rected outward in Microdon ( Aristosyrphus) , with stigmatic cross- 
vein (sc + r), with anterior crossvein (r + m) before middle of discal 
cell (2nd Mi +2) and without radial sector bristles. 
Abdomen: Males with four preabdominal segments, 1st abdominal 
