Samuel Wendell Williston.

Manual of the families and genera of North American Diptera online

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showed that there no living spider was in them, but almost
every one had an empty skin of a common spider Amaw'ohms



ACROCERII)^. 71

sylvestris, nearly full grown. The skin of the legs and thorax
were not clean like a moulted skin, but dirty and opaque, as
though eaten out, and the skin of the abdomen when present
was torn and shriveled. From this I concluded that the mag-
gots came out of the spiders, and from their size must have
nearly filled them. The maggots varied considerably in size,
the largest being a quarter of an inch long, while others were
not more than half as large. The hinder half of the body was
thicker than the front half and nearly spherical. They hung
head downward, holding to the web by their jaws and were
also partly supported by threads under and around them."
The author of the foregoing, J. H. Emerton, reared from other
specimens of these larvse a fly belonging to the genus Acrocera.
The larvae of Astomella Lindelii, according to Brauer, are so
lodged in the abdomen of the spider that the posterior termi-
nal stigmata are in relation with the lung-tubes of the spider.
The eggs are said to be deposited on dried twigs.

TABLE OF GENERA.

1. Antennse with a terminal bristle. ......

Antennffi without terminal bristle or style. . . . .

2. Antennae short, third joint rounded, with terminal bristly hairs.
Antennae elongate. .......... 7

3. Antennae inserted near the mouth. ...... 4

Antennae inserted toward the vertex. ...... 6

4. Wings with a stout costal spur near the tip of the auxiliary vein.

Pterodontia Gray.
Wings without such spur; anal cell absent. ..... 5

5. Proboscis rudimentary. ...... Oncodes Latreille.

Proboscis elongate, directed backwards (Central and South America).

PiiiLOPOTA Wiedemann.

C. Venation complete; eyes pilose Opsebius Costa.

Venation more or less obsolete; eyes bare. . . Acrocera Meigen.

7. Proboscis rudimentar}'. ........ .8

Proboscis elongate .......... 9

8. Eyes bare (Mexico). Appeleia Bellardi.

Eyes pubescent. ....... Ocnvea Erichson.

9. Ocelli wanting; large flics Lasia Wiedemann.

Ocelli present ; moderately large flies. . . Euloncha Gerstajcker.



72 NORTH AMERICAN DIPTERA.

25. LOKCHOPTERID^.

Small (2-4 mm.) slender, brownish or yellowish flies. An-
tennae short, porrect ; third joint simple, cirenlar in shape,
with a terminal bristle. Ocelli present. Scutellum with two
bristles. Legs long, bristly ; pulvilli very small ; empodia
wanting. Wings lancet-like, pointed ; the three basal cells of
moderate size and of nearly equal length ; fourth longitudinal
vein furcate and united with the fifth near the base ; first
longitudinal vein short, second and third not furcate ; the
anterior cross-vein lies near the base of the wing, in front of
the middle of the second basal cell and is oblique in position.

There is but one genus in this family, Lonchoptera, the
members of which are found, often in abundance, in the grass
or upon stones along the margins of shady brooks. The lar-
vae are flat with long bristles on the first, second and last seg-
ments ; posterior spiracles broadly separated on the last
segment, short and tubular. Head not differentiated, the
body composed of ten segments, the last one apparently com-
posed of two. Pupae enclosed in a puparium, orthorrhaphous.



26. EMPIDID^.

Small to moderately large, elongated, predaceous flies.
Head small, more or less spherical, not closely applied to the
thorax. Males holoptic or dichoptic, the front never exca-
vated. Antennse porrect, approximated at the base, composed
of three simple joints, the first two of which are often small ;
third joint variable in shape, with or without a terminal arista
or style. Face without mystax. Proboscis short or long,
projecting forward, downward or backward. Ocelli present.
Abdomen composed of from five to seven segments, male gen-
italia prominent and of complicated and variable structure ;
ovipositor projecting, pointed. Tegulse small. Legs often
with peculiar structural characters — the coxae or femora elon-
gated, the femora thickened and with spines below, the meta-



EMPIDID^.. 73

tarsi flattened, etc.; pulvilli present, the empodia usually
membranaceous and linear. Neuration variable ; the discal
cell sometimes absent, the third longitudinal vein furcate or
simple ; three or four posterior cells present ; anal cell often
shorter than the second basal cell, closed before the margin of
the wing*; sometimes wholly wanting.

The family Empididse is a large one, including many genera
and species. Most flies belonging here will be at once recog-
nized, but there are some, especially those of the subfamily
Tachydrominse, which have such peculiar neuratioii that they
are apt to lead the student astray ; some may even be sought
for among the smaller Muscids. The flies are all predaceous,
though obtaining part of their food at times from flowers.
Many species, especially those of Empis and Rhaniphomyia
often fly in swarms, dancing up and down over running brooks,
in the shade of trees or about shrubbery. Very rarely do any
species reach the length of ten millimeters, and some are not
more than three in length.

The larvae are cylindrical, with small swellings on the under
side, from the mesothoracic segments, for locomotion. They
are probably carnivorous and live in the earth, under leaves
or other decaying vegetable matter. The pupse are free, Avith
two porrect points at the anterior end.

TABLE OF GENERA.

1. Anal cell closed in the border or narrowly open; body without macro-

chaetge. Hilarimorphin^.

Anal cell closed before the border when present. ... 2

2. Anal cell wanting; when present the front femora shorter or but little

longer than their coxae Tachydrominje.

Anal cell present ; front femora much longer than their coxaa. . 3

* Mythicomijia, a genus of doubtful relationship, has the anal cell open.
In Hilarimorpha it is closed in the margin. Both genera also differ from
other Empididae in being destitute of macrochaetae. Osten Sacken and
Schiner locate the latter genus among the Leptidae. If tliat view is ac-
cepted, Mi/f/n'romi/ia sliould probably accompany it.

9



74 NORTH AMERICAN DIPTERA.

3. Posterior basal transverse vein, i. e. the vein which limits the anal cell,
parallel or nearly parallel with the hind border of the wing.

EmpidintE.
Posterior basal transverse vein not parallel with the hind border of the

wing. . ... . . . . • liYBOTINiE.

HILARIMORPHIN.^.
1. Second vein very short, terminating in the first ; discal cell present.

Mythicomyia Coquillett.
The second vein terminates in the costa ; discal cell wanting.

HiLARiMORPHA Schiner.

HYBOTIN^.

1. Third longitudinal vein furcate ; first submarginal cell closed.

Blepharoproctus Loew.
Third longitudinal vein simple 2

2. Anal cell shorter than the second basal cell. .... 3
Anal cell as long or longer than the second basal cell. ... 4

3. Third antennal joint conical; bristle terminal. Leptopeza Macquart.
Third antennal joint ovate; bristle subdorsal. Ocydromia Meigen.

4. Origin of the second longitudinal vein nearer the humeral than the an-

terior cross-vein; wings usually spotted. . Syneches Walker.
Origin not nearer the humeral cross-vein ; wings not spotted. . 5

5. Vein between the first and second basal cells indistinct. Syndyas Loew.
Vein between the first and second basal cells distinct. Hybos Meigen,



EMPIDIN^

1. Third longitudinal vein furcate.
Third vein simple. . . . .

2. No discal cell. ....
A discal cell present.

3. Proboscis distinctly longer than the head.
Proboscis not longer than the head.



2
Rhamphomyia Meigen.

Cyrtoma Meigen.
3



4. All the legs of nearly equal length; hind femora much thickened.

Pachymeria Stephens.

Hind legs longer than the others, their femora but little or not at all

thickened 5

5. Proboscis slender, directed backward or downward. . Empis Linne.
Proboscis moderately thickened, directed forward.

Iteaphila Zetterstedt.



EMPIDIDiE.



i o



C. Antennae very short, apparently two-jointed, the third joint compressed,

with a short, thick, unjointed style. . Hormopeza Zetterstedt.

Antennae not very short, distinctly three-jointed ; third joint awl or

pear shaped or spherical, with a two-jointed terminal style or

bristle. 7

7. Proboscis as long as the head, vertical ; anterior metatarsi usually thick-

ened in the $ Hilara Meigen.

8. Proboscis shorter than the head, horizontal ; anterior metatarsi of the

$ not thickened Gloma Meigen.



TACHYDROMIX^.

1. Third longitudinal vein furcate; discal cell present; anterior coxae much

elongate. ..... ..... 2

Third longitudinal vein simple; discal cell wanting. ... 5

2. Front femora nmch thickened ; two posterior veins arise from tlie discal

cell. ....... Hemeeodromia Meigen.

Front femora not much thickened ; three posterior veins arise from the
discal cell 3

3. Antennae with a long terminal bristle. . . Ardoptera Macquart.
Antennae with a short terminal bristle or style. .... 4

4. Sixth vein obsolete before reaching the margin. Clinocera Meigen.
Sixth vein not obsolete before reaching the margin ; antennae with a

very short terminal style. . . . Synamphotera Loew.

5. Anal cell, or at least the posterior basal cross-vein, present; antennse

with a long terminal bristle. . . . Tachydromia Meigen.

6



Anal cell wholly wanting.



6. Front femora thickened.
Front femora not thickened.

7. Arista terminal. ....
Arista subdorsal

8. Arista terminal. ....
Arista dorsal. ....

9. Proboscis short, vertical ; palpi broad.
Proboscis slender; palpi narrow, slender



7
, . . . 8

Tachypeza Meigen.
Pkoneutisca Loew.

Drapetis Meigen.
9

. Stilpon Loew.
Phoneutisca Loew.



76 NORTH AMERICAN DIPTERA.

27. DOLICHOPODID^.

BY PROF. J. M. ALDRICH.

Small ilies, never exceeding 7 mm. in length, almost always
green in gronnd color, usually shining, more rarely dusted
with gray or brown, sometimes pure yellow or almost black.
As a family they are distinguished from their nearest allies
by the absence of the cross-vein between the discal and second
basal cells, these uniting to form a single cell.

Head about as wide as the thorax (much wider only in
Psilopinse), usually a little wider than high ; the face bare,
very wide to very narrow, or the eyes contiguous below the
ante n nee ; front generally widening rapidly above (in Dia-
phorus the eyes sometimes contiguous above), with bristles
on the vertex only. Posterior orbit with a well defined row
of short, erect bristles (toward the mouth indistinct in Hydro-
phorinse and some other genera); proboscis fleshy, short,
retracted, rarely a little protruding ; antennie three-jointed,
inserted more or less above the middle of the eyes, the first
two joints never much elongated, the third commonly oval,
but in several genera lengthened ; arista dorsal, subapical, or
completely apical. Thorax higher and longer than wide, with
regularly arranged bristles on the dorsum ; in some genera a
well-marked flattened or concave area before the scutellum.
Abdomen tapering, conical or a little compressed (in Hydro-
phorus and Scellus sometimes peculiarly small and retracted),
without noticeable bristles in most genera ; the male hypopy-
gium usually prominent, varying greatly in form, and in the
degree in which it is concealed in the abdomen. Coxae gen-
erally short, legs in most genera of medium length, sometimes
elongated, those of the male frequently developed into some
ornamental structure ; the front femora are thickened in a few
genera. Wings usually hyaline, yet often with dark mark-
ings, which may take the form of a definite pattern, or may
follow the veins indistinctly, or may be evenly diffused; in



DOLICHOrODIIM^:. 77

some cases the males have small snow-white spots in the tip
of the wing. Anal cell always very short.

This family perhaps surpasses any other natural group of
animals in the variety of sexual ornaments possessed by the
males. These are paraded before the females, as are similar
ornaments in the peacock and turkey-cock. See " Courtship
Among the Flies ", American Naturalist, Jan. '94, p. 35.
They may occur in almost any external portion of the body.
In a careful examination of a large number of species, I have
never found any two in which they are identical. I am ac-
quainted with at least fifty different forms of tarsal modifica-
tion alone, every one of which is distinctive of its species.
Nevertheless some species seem to offer no noticeable sexual
differences beyond the presence of the hypopygium in the
male ; even this is in some cases but little visible.

In adult life all are predaceous, capturing chiefly the
minuter soft bodied flies, which they enclose within their soft
labella, while extracting the juices ; the larvae are, as far as
known, feeders on decaying vegetation.

The following table is designed solely to enable beginners
to determine the genera of their specimens : it does not, there-
fore indicate anything about the natural relations of the gen-
era to each other. It is based on male specimens only, since
otherwise it must have included many obscure and difficult
characters.

TABLE OF GENERA.

1. Fourth longitudinal vein with a widely divergent fork on the front side;

or if not, the head wider than the thorax, face wide, and the front
deeply excavated (Psilopinae). ....... 2

Fourth vein simple or merely broken, front not excavated. . .5

2. Fourth longitudinal vein not forked. . . Aptorthus Aldrich.
Fourth longitudinal vein forked. ....... 3

3. Tegular cilia black, third longitudinal vein curved gently back at tip,

scutellum with four large bristles. . . . Psilopus Meigen,
Tegular cilia pale, third vein distinctly curved forward at the tip, scu-
tellum with two large and usuallv two small bristles. . . 4



78 NORTH AMERICAN DIPTERA.

4. Face wide, front deeply excavated. . Gnamptopsiloi'ds Aldricli.
Face narrow, front scarcely excavated. . Leptorhethum Aldrich.

5. Fourth longitudinal vein bent forward, forming an apical cross-vein;

posterior cross-vein very oblique, parallel to the margin of the wing.

Plagioneurus Loew.
Posterior cross-vein nearly transverse, usually no apical cross-vein. 6

6. Hind metatarsi with large bristles above 7

Hind metatarsi without large bristles above 8

7. Face in male reaching the lower corner of the eye.

Hygroceleuthus Loew.
Face in the male not reaching the lower corner of the eye.

DoLiCHOPUs Latreille.

8. Hypopygium long, extending forward under the venter. . . 9
Hypogygium short, not extending forward under the venter. . 21

9. Arista short-plumose. .10

Arista pubescent or bare. ........ 12

10. Fourth vein beyond the posterior cross-vein gradually convergent

toward the third. ..... Poecilobothkus Mik.

Fourth vein shortly before the tip quite suddenly bent toward the
third.* 11

11. Hypopygium pedunculate, slender, without long, branching appendages

Pelastoneurus Loew.
Hypopygium sessile, with long, branching appendages.

Metafelastoneurus Aldrich.

12. Before the scutellum the posterior third of the thoracic dorsum is hol-

lowed out, or at least flattened down to a plane. ... 13
Before the scutellum convex as usual. 16

13. Hypopygium long, pedunculated. 14

Hypopygium short, sessile or nearly so. ..... 15

14. Bristles of the thorax yellow. . . Aphantotimus Wheeler.
Bristles black. Medeterus Fischer.

15. Color of body yellow, sometimes with a little black.

Neurigona Rondani.
Color of body chiefly metallic, sometimes dusted ; legs very long.

Dactylomyia Aldrich.



* If with a marked concavity toward the apex, see Paraclius, in which
the pubescence of the arista is rather strong.



DOLICHOPODIDiE. 79

16. The face of the male extends below the ej'es, hanging down before the

mouth, apron-like. .... Polymedon Osten Sacken.
The face of the male reaches as far down as the lower edge of the

eye 17

The face of the male does not reach so far as the lower edge of the

eye 18

17. Third antennal joint of the male rudimentary, the long arista with a

disk at the end Macellocerus Mik.

Antennae of simple structure. . . Tachytrechus Stannius.

18. Third and fourth veins towards the tip parallel or nearly so. . 19
Third and fourth veins toward the tip distinctly convergent. . 20

19. First antennal joint bare above, third joint elongate in the male.

Peloropeodes Wheeler.
Pirst joint hairy above. .... Gymnopternus Loew.

20. The last segment of the fourth vein gradually approaching the third.

Hercostomus Loew.
Last segment near the middle abruptly curving forward, then grad-
ually resuming its former course, making a segment of a circle, the
concavity outwards, and ending near the third vein.

Paraclius Bigot.

21. Costal vein extending to tip of third vein, the latter part of the fourth

vein evanescent or partially so. . . . Asyndetus Loew.

Costal vein extending to the tip of the fourth vein, which is of the

usual strength. ......... 22

22. Sixth vein wanting (minute species, not shining, the first vein reaching

only a fifth of the length of the wing). . . . Achalcus Loew.
Sixth vein present, at least for a short distance. ... 23

23. First antennal joint hairy above. ...... 24

First antennal joint bare above. ....... 29

24. Second antennal joint with a thumb-like projection fitting into the

inner side of the third Syntormon Loew.

Second antennal joint without such projection 25

25. Fourth vein before the tip sharply curved toward the third, nearly

reaching it at the margin. . . Metapelastoneurus Aldrich.

Fourth vein near the end parallel with the third or only moderately

convergent. *......-.. 26

26. Arista dorsal, third antennal joint of usual size, palpi of male large,

face wide Diostracus Loew.

Arista dorsal, palpi small, face very narrow. . Anepsius Loew.
Arista nearly or quite at tlie end of the large, pointed third joint. 27



80 NORTH AMERICAN DIPTERA.

27. Hind coxae witwout erect hairs on the outer side, third and fourth veins

near the tip convergent. .... Hypocharassus Nick
Hind coxae with one or more erect liairs, third and fourth veins paral-
lel, wings wide. ......... 28

28. Scutellum with smaller hairs on the disk besides the marginal bristles.

Lasiargyra Mik.
Scutellum bare, except for the bristles. . . Argyra Macquart.

29. Posterior tliird of thoracic dorsum, before the scutellum, concave or

at least distinctly flattened. . - 30

Dorsum rounded as usual. ........ 32

30. Bristles of thorax yellow Chrysotimus Loew.

Bristles black, rarely brownish. ....... 31

31. Fourth vein parallel with the third beyond the cross-vein, or nearly so.

Xanthochlorus Loew.

Eourth vein converging toward the third beyond the cross-vein, either

gradually or by a double curve. .... Go back to 15.

32. Wings elongate, tlie posterior cross-vein considerably beyond the mid-

dle, less than its length from the apex of the fifth vein (Hydropho-
rinae). .... ........ 33

Wings not elongate, cross- vein scarcely beyond the middle, more than
its length from the end of the fifth vein (if less, the hind metatarsus
shorter than the following joint). . . . . . . 35

33. Fore femora slender Liancalus Loew.

Fore femora more or less incrassated, with spines below. . . 34

34. Spines of fore femora very short, thoracic dorsum without well marked

poUinose lines . Hydrophorus Fallen.

Spines of fore femora long, dorsum with poUinose lines. Scellus Loew.

35. Outer appendages of the hypopygium long, filiform.

Nematoproctus Loew.
Outer appendages not long and filiform. ..... 36

36. Second antennal joint with a thumb-like projection along the inner

side of the third (Synarthrus Loew). . . . Syntormon.
Not with such prolongation. . .37

37. Eyes contiguous or nearly so below the antennae. ... 38
Eyes contiguous above the antennae. . . Diaphorus Meigen.
Eyes closest together at the level of the antennae, diverging above and

below ; middle legs of male distorted. . Campsicnemus Walker.
Eyes not approximated. . 39



DOLICHOFODID^.. 81

38. Pulvilli of male fore tarsi conspicuously enlarged. Eutarsus Loew.
Pulvilli of male not enlarged. . . . Chrysotus pt. Miegen.

39. Thorax bright green, abdomen yellow, with a good deal of silvery pol-

len Leucostola Loew.

Not so marked 40

40. Face broad, the palpi large, reposing on the proboscis; small, pollinose

species, with yellow antennae. . . Thinophilus Wahlberg.

Palpi of ordinary size or else projecting lamelliform, free from the

proboscis 41

41. The third longitudinal vein (in the male) keeps close to the second till

near the tip of the latter, then makes a wide curve backward; the

third and fourth veins farther apart tlian usual. Lyroneurus Loew.

Wings of ordinary structure. ....... 42

42. Third joint of antennae in the male conspicuously long, awl-shaped, not

wider at the base than the first joint, . . Khaphium Meigen.
Third joint long, lancet-shaped, wider at the base than the first joint.

PoRPHYROPS Meigen.
Third joint short, the tip sometimes drawn out into a point. . 48

43. Arista nearly or quite apical; fore pulvilli of male not enlarged.

Chrysotus, pt.
Arista dorsal or subapical; fore pulvilli of male elongated.

DiAPHORUS, pt.

Arista dorsal, inserted quite near the base of the joint; pulvilli plain;

abdomen of male slender, compressed. . . Sympycnus Loew.



10



82 NORTH AMERICAN DIPTERA.



CYCLOEEHAPHA.



28. SYPvPHID^.

Small to rather large flies. Head hemispherical, often elon-
gated or produced in the lower part; as broad or a little broader
than the thorax. Face moderately broad, bare or clothed with
dust or short pile ; excavated in profile under the a^ntennse
and projecting below, or with a distinct convexit}^ near the
middle part, never with longitudinal furrows or lateral ridges,
usually convex transversely, sometimes with a median ridge.
Oral opening large ; proboscis rarely much elongated. Front
never excavated. Antennae usually porrect and approximated
at their base, three-jointed, usually with a dorsal arista.
Eyes large, bare or pilose ; in the male usually contiguous
above. Ocelli always present. Thorax comparatively large
and robust, moderately arched above. Tegulse of moderate
size. Abdomen composed of five or six visible segments, rarely
with only four. Hypopygium usually not prominent. Legs
usually of moderate strength. Macrochsetse rarely present in
any part of the body ; the body generally thinly pilose or bare,
but sometimes clothed with thick pile. Wings comparatively
large ; third longitudinal vein never forked ; marginal cell
open or closed ; the fourth vein terminates in the third at or
before the tip ; three posterior cells ; basal cells large ; anal
cell always closed before the border of the wing ; between the
third and fourth longitudinal vein and nearly parallel with
them, a false or spurious vein, nearly always present and
characteristic of the fmriily.

The family Syrphidse is one of the most extensive in the
order. Nearly twenty-five hundred species are known through-
out the world and many new forms are constantly being added.
They contain amonsj them many of the brightest-colored flies,



SYRPHID^. 83

and numerous specimens are sure to appear in an}^ general
collection of insects. ISTone are injurious in their habits to
man's economy and many are very beneficial. In their adult
habits they all show a great uniformity. They are flower-
flies and feed upon honey and pollen, loving the bright
sunshine.

The larvae are usually not very elongate, with firm, some-
times tough skin, the head-segments small and extensile, the
head not distinctly differentiated. The external mouth-parts
are either wholly wanting, with only a soft fleshy opening, or
there are two or four outwardly directed booklets. Antennae
short, small, one or two jointed and fleshy. Body smooth or
provided with soft conical projections and bristles; below
usually with seven pairs of abdominal feet. At the posterior
end the body terminates in a more or less elongate tube, sin-
gle or double, the stigmata. This tube sometimes forms a
short, almost chitinized, tubercular projection on the dorsal
part of the last segment; at other times it is very long, longer
than the body, slender and composed of two joints, the one
sliding within the other, like the joints of a telescope. In
changing to the pupal condition, the larval skin contracts to
form the pupal envelope, and the body becomes shorter, more
oval and of a darker color, the elongated respiratory tube, in
the "rat-tailed" species, being curved over the back. Unlike
all the other Cyclorrhapha, except the Pipuuculidae, the fron-


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Online LibrarySamuel Wendell WillistonManual of the families and genera of North American Diptera → online text (page 11 of 18)