1969] 
Thompson — Microdontine Flies 
77 
spiracles embedded in metathoracic epimera. Genitalia: chitinous 
box usually spherical and without external lobes; ejaculatory process 
tubular and elongate; ejaculatory hood elongate, surrounding ejac- 
ulatory process, enclosing basal portion of the chitinous box, articu- 
lating dorsally with ioth sternite and ventrally with sustentacular 
apodemes; penis sheath without lobes, with posterior dorsal surface 
infolded and elongate posteriorly, where it is connected by membrane 
to the sustentacular apodemes when present; sustentacular apodeme 
usually present, absent or reduced in the specialized forms Mixogaster 
and Microdon ( Aristosyrphus) , double, fused anteriorly to form a 
broad curved plate articulating with ventral end of ejaculatory hood 
and connected posteriorly by membrane to dorsal infolded surface of 
penis sheath; ejaculatory apodeme triangularly flared apically except 
in Paragodon ; ejaculatory sac sclerotized and usually well-developed 
except in Paragodon. 
Larvae: The larvae are exclusively scavengers in ants’ nests and 
can be separated from other syrphid larvae by the following char- 
acteristics: i) lack of body segmentation (Heiss, 1938); 2) lack 
of segmental spines (Heiss, 1938); 3) absence of cibarial ridges 
(also in Syrphinae) (Hartley, 1963); 4) presence of sclerotised 
labial lips (Hartley, 1963); 5) mandibles of a different form than 
the normal saprophagous types (Hartley, 1963) ; 6) opening of 
puparium by three pieces, two dorsal lateral pieces, and one ventral 
piece instead of two dorsal pieces (Lundbeck, 1916). Some of these 
characteristics may not be of subfamilial value since the larvae of 
only Microdon s. s. have been studied in detail. The larvae of Mixo- 
gaster have been described by Greene ( 1955 ) and Carrera and Lenko 
(1958) and appear to agree with the above. However, the existence 
of larvae like N othomicrodon Wheeler (1924) (which may not be 
a syrphid) suggests that there may be much greater variability in the 
larval form than presently known. 
Type-genus: Microdon Meigen 
The genera. I include in the Microdontinae are the same as those 
listed by Hull (1949) except Spheginobaccha is excluded. Sphegino- 
baccha does not have a postmetacoxal bridge and lacks the specialized 
structures of the male genitalia. Indascia Keiser does belong to the 
Figs. 1-4, lateral view of heads; la, ventral view; 5-6, ventral view of 
metasterna and surrounding parts. Fig. 1 , Paragodon paragoides , n. sp., 
male (HT) ; 2. Paramicrodon delicatula Hull, male (LT) ; 3. Microdon 
(Ubristes) triangularis Curran, female; 4. Microdon (Rhoga) sp. A, female; 
5. Mixogaster cubensis Curran; 6. Microdon (Rhopalosyrphus) guntherii 
Arribalzaga. HT-Holotype, LT-Lectotype. 
