@Prohercostomus@, a New Subgenus of the Genus @Hercostomus@ Loew
(Diptera, Dolichopodidae) from Baltic Amber
I. Ya. Grichanov
All-Russian Research Institute of Plant Protection, Russian Academy of
Agricultural Sciences, Podbelskogo 3, Pushkin, St. Petersburg, 189620
@Abstract---A new subgenus of @Hercostomus@ Loew, @Prohercostomus@
subgen. nov. (Diptera, Dolichopodidae), is described for @Dolichopus
noxialis@ Meunier (type species; redescribed) and 6 other species, all
from Baltic amber. Subgenera of @Hercostomus@ are keyed.
Received July 1, 1996
Paleogene fauna of dolichopodid flies from Baltic amber is quite rich
but nevertheless rather poorly studied (Keilbach, 1982; Spahr, 1985).
The last monographic treatment of this fauna appeared in the beginning
of our century (Meunier, 1907, 1908a, b). Systematics of the family
considerably changed since. Very short species descriptions given by
Meunier often do not allow to determine even the generic position of
these taxa correctly. Some species were probably misplaced by him at
generic level, as already suggested by Negrobov (1978) for those which
were assigned by Meunier to the genus @Dolichopus@ Latreille, 1796.
Therefore a revision of this type material is urgently needed.
Unfortunately the present location of the type collection, which was
kept in the former Geologisch-Pal@aontologisches Institut, Universit@at
K@onigsberg, is unknown.
RESULTS AND DISCUSSION
A piece of Baltic amber purchased by me in Vilnius contains a male of
dolichopodid, doubtless belonging to the extant genus @Hercostomus@
Loew, 1857. This find confirms an opinion (Bickel, 1994) that recent
genera of Dolichopodidae have already appeared in the Paleogene.
Comparison of this specimen with the descriptions made by Meunier allows
to assign it to @Dolichopus noxialis@; his quite accurate drawings of
the antenna and fore and hind tarsus nearly exclude erroneous
identification. Related species described by Meunier under the genera
@Gymnopternus@ Loew, 1857 and @Dolichopus@ should be transferred to
@Hercostomus@ as well.
Recent fauna of the genus @Hercostomus@ comprises about 320 mostly
Holarctic species (Foote et al., 1965; Negrobov, 1991). Known tropical
species of this group will be probably excluded from the genus after
future revision (Robinson, 1970; Dyte, 1975). The taxonomy within the
genus turned out to be rather complicate, and in recent papers it is
usually divided into the subgenera @Hercostomus@ s. s., @Gymnopternus@
Loew, 1857, @Platyopsis@ Parent, 1929, and @Poecilobothrus@ Mik, 1878
(Pollet, 1990; Negrobov, 1991). Besides that, Stackelberg (1949) created
one more subgenus, @Microhercostomus@, for @Hercostomus dilatitarsis@
Stackelberg, 1949 from Kondara Gorge (Gissar Range, Tadzhikistan). The
only type specimen differs from all the other @Hercostomus@ species by
the absence of posterior crossvein (@m-cu@[ITAL]) in the wings. A
representative series collected by the author of this paper in 1979 in the
canyon of Varzob River, the type locality of this species (5 males and 5
females; Gissar Range, Takob Gorge, 1800 m; in collection of Voronezh
University). All the specimens are identical to the holotype except for
retaining @m-cu@ crossvein. Its absence is obviously an exception
(mutation), very rare in the subfamily Dolichopodinae. Therefore the
subgenus @Microhercostomus@ Stackelberg is considered a synonyme of the
nominative subgenus, @Hercostomus@ s. s.
A careful examination of @H. noxialis@ had shown that it could be
included into neither extant subgenus of @Hercostomus@. The species
combines the characters diagnostic for some of extant subgenera with
several obvious plesiomorphies, permitting to describe a new subgenus of
@Hercostomus@. The most characteristic of its plesiomorphies are the
unusual leg chaetotaxy, elongate R@1 vein, simple massive surstyli and
gonopods of males, etc. As judged from the habitus, this new subgenus
could be ancestral group to the others (except for @Poecilobothrus@).
The diagnosis of a new subgenus, a key to subgenera of @Hercostomus@,
and the detailed redescription of @H. noxialis@ are given below.
@Prohercostomus@ subgen. nov.
@Type species. @Dolichopus noxialis@ Meunier, 1907; Baltic amber.
@Diagnosis. Head with single pair of stout ocellar bristles. Postocular
setae black, numerous. Face narrow. Pubescense of arista undeveloped.
Thorax with single stout propleural bristle. Humeral tubercle with one
stout and several short bristles. Six dorsocentral bristles. Acrostichal
bristles in two series reaching fifth pair of dorsocentral bristles.
Posterior part of mesoscutum without dark hairs. Scutellum with two
stout bristles and two hairs on sides. Legs simple. Fore and middle
coxae with small hairs and several bristles in distal half, hind coxae
with single stout bristle. Middle and hind femora with single, stout but
short, anterior subapical bristle. Tibial bristles poorly developed,
scarcely as long as diameter of tibia; ventral bristles undeveloped;
dorsal bristles on fore and hind tibiae forming single series along
their whole length. Wing elliptical, about twice as long as wide; R@1
reaching wing midlength; R@4+5 and M@1+2 in distal wing half parallel;
anal lobe broad; alula undeveloped. Abdomen (including 8th segment) in
dark bristles. Hypopygium not large, without stalk; cerci simple;
surstyli and gonopods large, massive, relatively simple.
@Composition. Subgenus @Prohercostomus@ comprises following species (all
from Baltic amber):
@bickeli@ Evenhuis, 1994: 361 (@Dolichopus@), comb. nov.;
= @vulgaris@ Meunier, 1907: 221 (@Dolichopus@), comb. nov.;
@interceptus@ Meunier, 1907: 221 (@Gymnopternus@), comb. nov.;
@intremulus@ Meunier, 1907: 221 (@Gymnopternus@), comb. nov.;
@meunierianus@ Evenhuis, 1994: 361 (@Dolichopus@), comb. nov.;
= @notabilis@ Meunier, 1907: 221(@Dolichopus@), comb. nov.;
@monotonus@ Meunier, 1907: 221 (@Dolichopus@), comb. nov.;
@negotiosus@ Meunier, 1907: 221 (@Dolichopus@), comb. nov.;
@noxialis@ Meunier, 1907: 221 (@Dolichopus@), comb. nov.;
Key to subgenera of @Hercostomus@
1. Arista with pubescense long (about 1.5 times as long as basal width
of arista); distinct purple spot in notopleural pit; male cerci elongate
triangular with ventral margin strongly incised .................
- Arista bare or rarely pilose; notopleural pit normally without purple
spot; cerci variously shaped ....................... 2
2. Face broad, parallel-sided; epistome concave, clypeus convex; palps
relatively large and wide; first metatarsomere with single ventral
bristle ........ @Platyopsis@
- Face at least in male relatively narrow; clypeus not or at most
weakly convex; palps normally small, rarely large and elongate; first
metatarsomere without stout ventral bristle ....... 3
3. Tibial bristles poorly developed, scarcely as long as diameter of
tibia; ventral bristles undeveloped; dorsal bristles on fore and hind
tibiae forming single series along their whole length; R@1 reaching wing
midlength; male surstyli and gonopods massive, simple ........
@Prohercostomus@ subgen. nov.
- Tibial bristles (including ventral ones) usually well-developed;
dorsal bristles at least in basal half of fore and hind tibiae divided
into anterodorsal and posterodorsal; R@1 usually not reaching first
third of wing length; male surstyli and gonopods complicately shaped,
often slender ........... 4
4. Metapleuron with group of hairs before posterior spiracle; mesoscutum
posteriorly and scutellum dorsally hairy; R@4+5 and M@1+2 parallel
- Metapleuron and posterior mesoscutum usually bare; scutellum usually
with two stout bristles and two marginal hairs; R@4+5 and M@1+2 usually
converging ............. @Hercostomus@ s.s. (@Microhercostomus@, syn.
@Hercostomus (Prohercostomus) noxialis@ (Meunier, 1907)
@Dolichopus noxialis@ Meunier, 1907: 221, 1908a: 46, 1908b: 88, 1912:
179; Keilbach, 1982: 375; Spahr, 1985: 34; Evenhuis, 1994: 362.
@Types. In the collection of former Geologisch-Pal@aontologisches
Institut, Universit@at K@onigsberg (location unknown).
@Description (Fig. 1). General coloration of the head, thorax and
abdomen is dark, with metallic shine, at certain illumination shot with
green. Pollinosity and minute pale hairs are virtually
indistinguishable. Face is narrow (ratio of its width below antennae to
height 8 : 27); clypeus is not convex, twice narrower than epistome.
Antenna is entirely dark, with 2nd segment rounded and 3rd segment
elongate triangular (twice as long as high), apically acuminate; arista
lacks distinguishable pubescense, consists of two segments, and
originates in distal third of 3rd segment. Ratio of the lengths of 1st
to 3rd antennal segments to the height of 3rd segment and lengths of 1st
and 2nd segments of arista is 5 : 4 : 13 : 7 : 7 : 30.
Legs are mostly pale, except for dark middle and hind coxae, hind tibiae
in distal half, fore and middle tarsi (except for the base of first
segment), and hind tarsi. All legs are simple, with short black bristles
scarcely exceeding in length the diameter of the respective podomeres.
Fore and middle coxae are covered with small hairs, with several
bristles in distal half. Hind coxae bear a single stout outer bristle.
Middle and hind trochanters bear a single stout dorsal bristle. Fore
femora bear one to three posteroventral subapical hairs. Fore tibiae
bear a series of 10 short but stout dorsal bristles along their whole
length, with elongate anteroventral bare area in distal half; other
bristles are lacking. 1st segment of the fore tarsi bears a ventral
series of very short, scarcely visible spinules. Middle femora bear a
single, short but stout, anterior subapical bristle and several
posteroventral subapical hairs. Middle tibiae bear two anterodorsal, two
to three posterodorsal, and five to six apical bristles. Hind femora
bear one short but stout, anterior subapical bristle, several
posteroventral subapical hairs, and a series of short but distinct,
dorsal hairs in basal half. Hind tibiae bear a series of 12 short dorsal
bristles along their whole length, and several very short apical
bristles. Ratio of the lengths of coxa, femur, tibia, and 1st to 5th
tarsomeres is for the fore legs 35 : 52 : 45 : 27 : 13 : 10 : 6 : 6, for
the middle legs 27 : 55 : 57 : 28 : 15 : 12 : 9 : 8, and for the hind
legs 20 : 65 : 63 : 70 : 25 : 15 : 10 : 9.
Wings are elliptical and lack spots. Costal vein lacks thickenings. R@1
reaches wing midlength. R@2+3 is nearly straight. Ratio of the section
of costal vein between R@2+3 and R@4+5 to its section between R@4+5 and
M@1+2 is 23 : 14. R@4+5 and M@1+2 are parallel in distal wing half and
both slightly curved towards posterior wing margin. M@1+2 joins costal
vein a little beyond wing tip. Ratio of the proximal and distal sections
of M@1+2 is 65 : 71. Crossvein @m-cu@[ITAL] is slightly convex and forms
right angles to both longitudinal veins. CuA@1 reaches the wing margin.
Ratio of the proximal and distal sections of CuA@1 to @m-cu@ is 65 : 34
: 16. Anal vein ends not reaching the wing margin; anal angle is right.
Calypters are poorly distinguishable, pale (?) with dark (?) setae.
Halter is pale.
Abdomen bears dark bristles, dorsally and laterally the short ones,
ventrally (on 2nd to 4th sterna) the long ones. 8th segment bears stout
dark bristles. Hypopygium with appendages is dark, shorter than the
length of 4th--6th abdominal segments combined. Epandrium bears very
short and dense erect hairs dorsobasally. Cerci are flat, elongate oval,
with narrow apex, densely beset with long dark bristles. Surstyli are
elongate triangular, massive, a little shorter than cerci, with a small
ventrobasal lobe; their apices are weakly curved ventrad and bear at
least two small bristles. Gonopods are long, massive, curved dorsad,
slightly widened at apex, with an apical hair as long as surstyli.
Hypandrium and the bases of gonopods are concealed by the last abdominal
@Measurements (mm): body length 2.6, length of wing 2.5, length of
@Comparison. @H. (P.) noxialis@ is clearly distinct from other species of
the subgenus described by Meunier in the shape of 3rd antennal segment
(1st flagellomere) and ratio of tarsomeres. In the ratio of length and
height of 3rd antennal segment this species is most similar to @H. (P.)
meunierianus@, being distinct from the latter in the arista originating
in distal third of 3rd segment, and in the 1st segment of fore tarsi
being twice longer than the 2nd one.
@Remarks. The difference between yellow, orange, brown, and purple
colors, which are quite widely used in diagnostics of the recent species
of @Hercostomus@, is masked by coloration of the amber.
@Material. Completely preserved male in the piece of Baltic amber
labelled: Baltic Amber: Vilnius, 13.04.1996, I.Y. Grichanov (in author's
collection); Upper Eocene--Lower Oligocene.
Dyte, C.E., Family Dolichopodidae, in @A Catalog of the Diptera of the
Oriental Region@, Honolulu: Univ. Haw. Press, 1975, vol. 2, pp. 212--
Evenhuis, N.L., @Catalogue of the Fossil Flies of the World (Insecta:
Diptera)@, Leiden: Backhuys, 1994.
Foote, R.H., Coulson, J.R., Robinson, H., Family Dolichopodidae, in @A
Catalog of the Diptera of America North of Mexico@, U. S. Dept. Agric.,
Agricult. Handb., 1965, no. 276, pp. 482--530.
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@Naturaliste@, Paris, 1907, vol. 29, pp. 197--199, 209--211, 221--222,
233--235, 245--246, 260--262, 269--271, 281--282.
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@Naturaliste@, Paris, 1908a, vol. 30, pp. 7--9, 21--23, 29--30, 45--46,
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Paris: Publications du Journal Le Naturaliste, 1908b, pp. 1--100.
Meunier, F., Coup d'oil r@etrospectif sur les Dipt@eres du succin de la
Baltique, @Ann. Soc. sci. Bruxelles@, 1912, vol. 36, pp. 160--186.
Negrobov, O.P., Flies of the Superfamily Empidoidea (Diptera) from
Cretaceous Retinite, @Paleontol. Zh.@, 1978, no. 2, pp. 81--90.
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Vol. 7. Dolichopodidae--Platypezidae@, Budapest: Akad. kiado, 1991, pp.
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Subgenus @Hercostomus (Gymnopternus)@ in Western Europe with the
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the Americas South of the United States@, S@ao Paulo: Museu de Zoologia,
Universidade S@ao Paulo, 1970, vol. 40, pp. 1--92.
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und Liste der Bernsteinfossilien -- Ordnung Diptera, @Stuttgarter Beitr.
Naturk.@, 1985, B, no. 111, pp. 1--146.
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Dolichopodidae) of Middle Asiatic Fauna, @Tr. Zool. Inst. Akad. Nauk
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Fig. 1. @Hercostomus (Prohercostomus) noxialis@, hypopygium in right