F. Christian Thompson.
A New Genus of Microdontine Flies (Diptera: Syrphidae) with Notes on the Placement of the Subfamily.
Psyche 76(1):74-85, 1969.

This article at Hindawi Publishing: https://doi.org/10.1155/1969/62102
CEC's scan of this article: http://psyche.entclub.org/pdf/76/76-074.pdf, 800K
This landing page: http://psyche.entclub.org/76/76-074.html

The following unprocessed text is extracted automatically from the PDF file, and is likely to be both incomplete and full of errors. Please consult the PDF file for the complete article.

A NEW GENUS OF MICRODONTINE FLIES
(DIPTERA: SYRPHIDAE) WITH NOTES ON
THE PLACEMENT OF THE SUBFAMILY1
I discovered the following new genus of Syrphidae while reviewing the Neotropical Microdontinae. I had planned to put aside its de- scription until my study of the subfamily was finished. However, publication of a second species assignable to it by van Doesburg (1966) has necessitated publishing a name now for this genus so that it can be included in the Catalog of South American Diptera. Paragodon, new genus3
Very small (4-5 mm,) microdontine flies. Face simple (slightly produced in paragoides) ; cheeks absent, eyes bordering on the oral opening; eyes dichoptic in both sexes; occiput evenly developed. An- tennae short, about one-half as long as face; aristae short and thick- ened.
Thorax about as long as broad; pleura bare except mesopleura pilose and metapleura with microscopic pile; scutellum without apical spines and fringe; metasterna undeveloped and bare; metathoracic spiracles without hair fringes. Legs simple, with no basal setal patches on the femora and with cicatrices only on the hind femora. Wings without the spurious vein, with all apical crossveins straight. Abdomen oval, lateral margins slightly emarginate and rolled under ventrally, with 1st sternite bare and 1st spiracles without hair fringes. Genitalia simple; ejaculatory apodeme simple, apical por- tion not triangularly flared; ejaculatory sac not sclerotized; ejacula- tory process single, short, not posteriorly fused to ejaculatory hood ; ejaculatory hood with anterior ventral portion elongate; sustentacu- lar apodeme present, double, fused anteriorly to base of ejaculatory 'Contribution no. 1392 from the Systematics and Morphology Research Laboratory, Department of Entomology, University of Massachusetts. Pub- lished with the aid of a grant from the Guy Chester Crampton Research Fund of the University of Massachusetts. '10 Edmunds Road, Wellesley Hills, Massachusetts, 02181. Personal Con- tribution no. 6.
'The name Paragodon is formed by adding the first part of Paragus to the last part of ..Microdon, thus indicating these flies' resemblance to Paragus and their phylogenetic affinity to Microdon. Manuscript received by the editor April 20, 1969 Pachc 76:74-85 (1960). hup Wpsycht einclub orgi76?76-074 html



================================================================================

Thompson - Microdontine Flies
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 (plesi~mor~hic) 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 ant's nests like all other microdontine flies? And could Paragodon possibly be the adults of Wheeler's .??othomicrodon? 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 (R ho&dosyrphus), 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, I st abdominal



================================================================================

76 Psyche
[March




================================================================================

19691 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 10th 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 (Afistosyrphus), 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 Nothomicrodon 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 S~he~inobaccha 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 (Ubnstes) triangularis Curran, female; 4. Microdon (Rhoga) sp. A, female; 5. Mixogaster cubensis Curran; 6. Microdon (Rhopalosyrflhus) guntheril Arribalzaga. HT-Holotype, LT-Lectotype.




================================================================================

Psyche
[March




================================================================================

19691 Thompson - Microdontine Flies 79
Microdontinae, not to the Cheilosinae as supposed by its author (Keiser, 1958).
Since Rondani (1856-57) first divided the Syrphidae into super- generic groups, most authors have accepted the Microdontinae as a distinct and separate group. However, Williston ( I 886) , Goffe (1952), and Wirth et d (1965) have treated it as a tribe in one or another subfamily. Williston placed the "tribe" Microdontini in the Syrphinae, and Goffe and Wirth et al have placed it in the Milesinae (Sphixinae Goffe). The relative ranking of a group depends on its position in the phylogeny of the whole group, so when one finds a group given two different rankings by different workers one expects to find differences in their phylogenies of the group. This is the case with the Microdontinae. Hull (1949) has placed the Microdontinae with the Eumerinae and Nausigasterinae in his first ~h~logenetic dichotomy of the Syrphidae; whereas Goffe ( 1952) considers the microdontines to have diverged long after the Syrphinae. These different views of the phylogeny of the Syrphidae can best be illustrated and compared by Hennig-type diagrams. The follow- ing diagrams (see text figure) illustrate the interpretations of Goffe ( 1952), Wirth et a1 ( 1965), and myself ; I follow Hull ( 1949) except that I exclude the Eumerinae and Nausigasterinae from the Microdon line. Plan I, my arrangement, clearly indicates that the Microdontinae should be considered the first divergence in the phylo- geny of the family. Only one character state (#8) could be used to place the microdontine divergence second. If the reduction of preabdominal segments in the male (character #8) is not convergent in the Microdontinae and Pipizini, then the Microdontinae would have to be considered to have arisen after the Syrphinae (Plan 2). Plan 2 explains Goffe's (1952) groupings. However, it is difficult to follow Goffe's "phylogenetic reasoning", which seems inconsistent with the modern "synthetic" theory of evolution and systematics. This plan creates more convergences than it solves. It seems to me more logical to consider the reduction of a character - in this case reduction of the abdominal segments in the male- as due to con- vergence than to suppose the development of a highly complex char- acter such as aphidophagous larvae to be convergent. Fig. 7, lateral view of male genitalia with axial system removed; 7a, lateral view of penis sheath and axial system; 8, ejaculatory apodeme and sac; 9-10, dorsal view of abdomen. Fig. 7, Paragodon paragoides, n. sp. (HT) ; 8. Microdon
(Cerioimicrodon) petiolatus Hull (HT) ; 9, Paragodon jtwragodes, n. sp. (HT) ; 10, Paragodon minvtula van Doesburg (after van Doesburg, 1966).




================================================================================

Psyche
[March
Wirth et a1 (1965) have used the larval state to define the first phylogenetic divergence and thus to define subfamilies of the syrphids (Plan 3). This arrangement too creates more ~roblems than it solves. Placing the syrphine before the microdontine divergence leaves no synapomorphic characters for the Milesinae and creates even more convergences than Plan 2.
In short, Plan I seems to offer the most logical illustration of the relationship of the Microdontinae to the other syrphids. However, much is still to be learned about the phylogeny of the Syrphidae, and my placement of the Microdontinae must be accepted only as the best possible present arrangement. The strongly plesiomorphic na- ture of the subfamily suggests that the microdons might best be considered as a separate family (as Martin ( 1968) has done with the Leptogasteridae) . However, regardless of the phylogenetic posi- tion of the microdontine flies, they should be clearly recognized as a subfamily equivalent to the Syrphinae and Milesinae. No other groups have been derived from the microdontine line. Hull (1949) included the Eumerinae4 and Nausigasterinae4 in the microdontine divergence. However, these groups belong to the mile- sine line and are probably derived from a myoleptine ancestor. Eumerinae and Nausigasterinae could not have evolved from the Microdontinae for a number of reasons. Both of these groups lack a number of the specialized characteristics of the Microdontinae which one would expect to find in any derived group; for example, they lack I) a complete postmetacoxal bridge, 2) the dorsal infold-
ing of the penis sheath, 3) the double sustentacular apodeme or its absence, and 4) other genitalic characters. It is also highly unlikely that the phytophagous larvae of Eumerinae and the saprophytic larvae of Nausigasterinae could have evolved from a specialized larval form like Microdon which lacks segmentation and segmental spines and possesses specialized mouthparts.
PROVISIONAL KEY TO THE NEW WORLD GENERA AND SUBGENERA OF MICRODONTINAE
I. Abdomen petiolate ; metasterna undeveloped, reduced to a thin line and bare (Fig. 5) ........................ Mixogmter Macquart Abdomen usually not petiola,te ; if petiolate then metasterna well- developed, not reduced and usually pilose (Fig. 6) .......... . 2 *The use of these groups as subfamilies follows Hull (1949) ; I presently regard these two groups as forming one tribe with Merodon, Allpumilio and Psilota under the Milesinae.




================================================================================

19691 Thompson - Microdontine Flies 81
Pteropleura bare ........................................ Paragodon Thompson ........................................................................ P teropleura pilose 3 Antennae short, less than one-half as long as face; first antennal segment never more than twice as long as broad (Fig. 2) .... ........................................................... Paramicrodon de Meijere Antennae long, always longer than one-half as lo'ng as face; first antennal segment always much more than twice as long as broad (Figs. 4 & 5) .................... Microdon Meigen ........ 45 Apical cross-vein angled outward on anterior one-half (Fig. 11) ................................................................ Aristos~rphus Curran Apical cross-vein not so, straight or slightly curved inward ........ 5 Barrette (dorsal portion of hypopleura,) bare ............................ 6 Barrette pilose .................................... Rhopalosyrphus Giglio-Tos Hind tibiae with distinct brushes of pile6 .................................... 7 Hind tibiae without brushes ........................................................ 8 Occiput uniformly developed, collar-like (Fig. 4) .................... ................................................................................... Rhoga Walker Occiput not uniformly developed (Fig. 3) ........ Ubristes Walker Anterior mesopleura bare; abdomen petiolate, petiole as long as thorax or longer; face slightly bulging below ............................ .................................................................... Cerioimicrodon Hull Anterior mesopleura pilose; abdomen usually not petiolate ; if petiolate, then petiolate short and face not bulging below ........ ...................................................................... Microdon Meigen Key to the species of Parapodon
Face with medial brown stripe; hind tibiae black ........................ ................................................ paragoides, new species (Mexico) Face without medial brown stripe ; hind tibiae whitish yellow .... ................................... minutula van Doesburg 1966 (Surinam) Paragodon paragoides new species
Face slightly produced medially, yellowish, with a diffuse medial brown stripe; thorax and abdomen brownish with yellow spots; legs black except front four tibiae and all tarsi orange. Male. Plead: face yellowish white except for diffuse medial brownish area, with white pile; front and vertex brownish black with pale pile; occiput black, grayish pollinose, with pale pile. Face narrower at oral opening than width of vertex, widest at base of "On the whole the separation of Microdon into subgenera, couplets 4-8, is not satisfactory. I do not recognize these subgenera as anything more than distinctive species groups.
'Not all Ubristes types have distinct brushes of pile.



================================================================================

Psyche
[March
Figs. 11-12, wings; 11, .Microdon (Aristosyrphus) primus Curran; 12, Paragodon paragoides, n. sp. (HT) .
antennae, and slightly produced between oral margin and antenna1 bases; front wider than face. Antennae short, about one-third length of face; first two segments black with black pile; third segment pointed apically, light brown, with small round sensory pit near middle on ventral portion. Aristae short, about as long as third segment, thick, light brown. Antenna1 ratio : 2 :I :6. Thorax: brownish black except for humeri, postalar calli and dorsal surface of stenopleura dirty white; thoracic pile yellow except for transverse }-shaped spot of black pile above each wing base. Wings grayish, almost completely microtrichose, with bases of first and second basal cell bare; wing venation as figured (Fig. 12). Halteres yellow. Squamae gray with dark margins. Legs black except as follows:
tips of femora, front four tibiae, and all tarsi orange; with pile dark except for light pile on front four tibiae. Abdomen: Dorsum with black and yellow pattern as figured (Fig. 9) ; venter yellow; abdominal pile appressed black on black areas and pale yellow on yellow areas.
Genitalia: as figured (Fig.
7, 7a) ; brown.
Holotype - male : Mazatlan Sinaloa, MEXICO ; I 6 August I 964,



================================================================================

19691 Thompson - Microdontine Flies 83
at sea level ; J. F. McAlpine, collector; holotype in Canadian National Collection, Ottawa.
Discussion : Paragodon paragoides is distinct f 1-om ininutula van Doesburg, the only other known species of Paragodon. Besides the key characters and abdominal patterns (Figs. 9, 10) paragoides shows the following differences from minutula: I) face produced forward in middle (Fig. I) ; 2) sides of face not parallel, converging to oral margin; 3) third antenna1 segment three times as long as first, not equal; 4) an appendix present on second vein (connected to third vein on one side) ; 5) with spurs on first and second pos- terior cells.
ID
0
. -
-==,
0
*
0)
c
0 0
-8
c .-
. -
s
,,, .å 3 .c
0
-c
0) .N
- S s, .åÁ
.- z z w .- a g 5 5 s " Q åÁ >s
z
w
8 6
7 3
6 2
5 7
4 8
3 7
2
7
Plesiornorphic
Apomorphic
^Convergent
Explanation of Argumentation plans. Apomorphic character states: 1, Single sustentacular apodeme; 2, complex faces; 3, absence of cicatrices on legs; 4, dorsal infolding of penis sheath; 5, lack of segmentation and seg- mental spines in the larvae; 6, carnivorous larvae; 7, bare humeri; 8, four preabdominal segments in the male.




================================================================================

84 Psyche [March
The nomenclature used in describing the genitalia of the male is that of Metcalf (1921).
ACKNOWLEDGMENTS
I would like to thank Dr. J. R. Vockeroth for the loan of this material and Mr. Charles H. Nelson for his critical comments on this manuscript.
REFERENCES
CARRERA, MESSIAS, AND KAROL LENKO
1958. Descricao de duas especies novas de Mixogaster (Diptera, Syrphidae) e observacoes sobre o inquilinismo de uma delas em ninhos de Iridomyrmex humilis, a "formiga argentina". Studia Ent, 1(3-4) : 469-484.
VAN DOESBURG, P. H.
1966. Syrphidae from Suriname, Stud. Fauna Suriname 9: 61-107 (The Hague).
GOFFE, E. R.
1952. An outline of a revised classification of the s~rphidae on phylo- genetic lines.
Trans. SOC. Brit. Ent. 11 (4) : 97-119.
GREENE, C. T.
1955. Larvae and pupae of the genera Microdon and Mixogaster (Diptera, Syrphidae). Trans. Amer. Ent. SOC. 81: 1-20. HARTLEY, J. C.
1963. The cephalopharyngeal apparatus of syrphid larvae and its re- lationship to other Diptera Proc. 2001. SOC. London 141 (2) : 261-280.
HEISS, E. M.
1938. A classification of the larvae and puparia of the Syrphidae of Illinois exclusive of aquatic forms. Illinois Biol. Monog. 16 (4)) 142 pp. in Univ. 111. Bull. 36(1) : 1-142. HULL, FRANK M.
1949. The morphology and inter-relationship of the genera of syrphid flies, recent and fossil. Trans. 2001. SOC. London 26 (4) : 257-408. KEISER, FRED
1958. Beitrag zur kenntnis der syrphidenfauna von Ceylon (Dipt.). Revue Suisse 2001. 65 (1) : 185-239.
LUNDBECK, WILLIAM
1916. Diptera Danica. Part V, Lonchopteridae, Syrphidae. 591 pp. (Copenhagen).
MARTIN, CHARLES H.
1968. The new family Leptogasteridae (The Grass Flies) compared with the Asilidae (Robber Flies) (Diptera). J. Kansas Ent. SOC. 41 (1) : 70-100.
METCALF, C. L.
1921. The genitalia of Male Syrphidae. Ann. Entomol. Soc. Amer. 14: 169-228.




================================================================================

19691 Thompson - Microdontine Flies 8 5
RONDANI, C.
1857. Dipterologiae Italicae prodomus. Vol. 2 (contains the syrphids). 264 pp. (Parma).
WHEELER, W. M,
1924. Two extraordinary larval myrmecophiles from Panama. Proc. Natl. Acad, Sci. 10: 237-244.
WILLISTON, S. W.
1886. Synopsis of the North American Syrphidae. U.S. Natl. Muse Bull. 31: i-xxx) 1-335. (actual date 1887). WIRTH, W. W., Y. S. SEDMAN AND# H. V. WEEMS, JR. 1965. Family Syrphjdae. IN Stone, A.) Sabrosky, C., Wirth, W. W., Foote, R. H,, and Coulsen, J.
1965. A catalog of the Diptera of
America north of Mexico. U.S. Dept. Agr. Handbook no. 276. 1696 pp.




================================================================================