TAXONOMY OF MUSCOIDEAN FUES — TOWNSEND 79

representing" the front

margin and

the right angle cut off truncate to represent the hind margin.

The

first

segment

consists above

and on

sidesof a strip-like dorsal plate evenly Repressed

between

^{its lateral} edges,

which

are tucked-up

rounded

folds of the plate, the latter ending ventrally

on

each side in a short,pointed stripthat does not

meet

the ventralplate, the ven-

tral

membrane

intervening

between

them.

A

^{small spiracle, smaller}

than

any

of the others of

abdomen,

ispresent in the

extreme

point of the first dorsal plate

on

each side

where

it joins the ventral

mem-

brane,

and

each one of the other five dorsal plates has a similar but larger spiracle

on

^its inner edge, these being in each case quite well

removed from

the lateral

margin where

it joins ventral

membrane.

The

third ventral plate is nearly rectangular, a little broader than long, aboutas

wide

as

mean

width of secondplate.

The

fourth ven-

tral plate is considerably broader than the third

and much

shorter, thus looking like a

narrow

transverse ^strip set in the ventral

mem-

brane.

The

fifth ventral plate is

much

wider than fourth, about

same

length,

and

its

median

portion (about middle one-third) ap- pears to be

crowded under

the fourth plate

by

the walls of the sheath-like genital opening, partially retracted within

which

^{lies the}

hypopygium. Thus

only the lateral one-third of the fifth plate is visible

on

each side,

and

these

two

portions

form

the

narrow

visible strips of the curved plate, bordering the edge of the genital opening

on

each side,

and

each pointed at its outer extremity.

The

sixth

abdominal segment

is not apparent

from

a dorsal view.

It is a shortened anal

segment

that has been

pushed

over

and crowded

beneath the extremity of the

abdomen.

It lies just

under

the posterior edge of the

abdomen,

is rather crescent-shaped, sub- semicircular

on

posterior (appearinganterior

owing

to inverted posi- tion)

edge where

it encloses the basal

segment

of the

hypopygium,

slightly squared

on

anterior lateral corners. It little

more

than half surrounds the orifice of the genital cavity,

and

bears a spiracle on each side at

some

distance before the pointed

end

of its tapering lateral portion.

The

basal sclerite or plate of the

hypopygium

bears another spiracle,

which

is one of the largest in the

abdomen,

on its

basal edge, near the spiracle of the sixth

segment and

appearing as

if it belonged tothat segment. This basal plate of the

hypopygium

represents another abdominal segment,

and

^it should be considered as

forming

a seventh

segment

of the

abdomen

^{rather than the base} ofthe

hypopygium.

The

ventral

membrane

is widely apparent

and

extensive, the ven- tral plates all lying free within it so far as contact with the dorsal plates is concerned.

The

area in

which

the ventral

membrane,

with

6

80 SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. 51 the enclosed ^plates, is visible occupies

more

than one-third the

width

of the ventral aspect of

abdomen.

The

^plates, both ventral

and

dorsal, are at once distinguished

throughout

their extent

from

the

membrane by

being clothed with bristly hairs.

The above

description

was drawn from

a

specimen

collected

by

F. C. Pratt, at Poolesville,

Maryland,

July 9.

The abdomen was

detached

and

put

under

^the microscope.

CEDEMASOMA,

gen. nov.

This form

(male) agrees with the description of

Wahlbergia

brevipennis

H. Loew,

except that the fourth vein is bent at a

rounded

angle,

and

hind crossvein is not strongly oblique.

The

hind crossvein is straight, almost at right angles to the fourth vein, hardly nearer to

bend

of latter than to small crossvein,

and

at right angles tofifth vein.

The

petiole of apical cell is slightly longer than small crossvein, but not twice as long

—

^{about one}

^and

^one-fourth

times as long.

The abdomen

is swollen

and

strongly

convex

above, wider thanthe thorax, exactly oval in outline

from

above, the

wider end

forward, absolutely without macrochaetae. Palpi are extremely small, almost atrophied, very slender

and

quite short. Antennae as long as face, second joint almost as long as third.

No

orbital bristles.

Wings

very short

and

narrow.

The

claws are about as long as last tarsal joint.

Type,

the following species

:

CEdemasoma

nuda, sp. nov.

One

male,

Ormsby

County,

Nevada,

July 6, C. F. Baker, Coll.

Length,

6 mm.

^; of wing, 4

mm.

Face, parafacials

and

para- frontals

from above

silvery white pruinose, blackish

from

in front, the silvery extending

on

cheeks. Frontalia silvery white pruinose, with a faint brassy tinge or a golden reflection.

Abdomen

densely covered with moderately short

and

fine

brown

or black hairs,

and

entirely withoutbristles, wholly yellowish red or

brownish

red.

The mesoscutum

is silvery pollinose in front of suture, but it does not

show

well in

some

lights. Tegulae white. Palpi pale reddish

brownish

in color. All the rest of insect is black, except the clear wings,

which

are yellowish at base.

Otherwise

agrees with

Loew's

description of

Wahlbergia

"brevipennis.

This form

apparently belongs inthe

neighborhood

of

Gymnosoma,

indicated

by

the absence of macrochaetae

and

the possession of a swollen

abdomen.

JVahlb. brevipennis

H. Loew

is this genus, but a different species.

Loew's

specimen is a female

from

Nebraska,

TAXONOMY

OK

MUSCOIDEAN

FLIES

— TOWNSEND

8l length 4§

mm.,

of

wing

₃

mm. The

writer has

examined

the type in

Cambridge. The

hindcrossvein does not

form

a right angle with

fifth vein, the petiole of apical cell is fully twice as long as small crossvein, the

head

is black

and

shining except face,

and

the

meso- scutum

does not

show

silvery before suture.

Type.—

Cat.

No.

10,898,

U.

^{S. N.}

M.

Subfamily Ocypterin.e Genus Ocyptera Latreille

Ocyptera euchenor

Walker. — ^While

^it

^seems

^{probable that this}

form and

epytus

Walker

are the same, there can be

no

certainty in the matter until the types are compared. Probably 0. Carolina

Robineau-Desvoidy

is distinct.

Some

of Bigot's species

may

also prove distinct. It

seems

probable that Carolina is a southern form,

and

that euchenor is the

more

northern large form,

having

the cheeks

and

parafacials narrow,

and

the eyes elongate, descending low. Further study

may

also

show

the distinctness of dosiades.

Genus Beskia Brauer and von

Bergenstamm

Beskia cornuta

Brauer and von Bergenstamm and

allies.

—

B. cor- nuta is the

South American

form.

The

type is

from

Brazil.

The

figure of the

head

given

by

^the authors (fig. 276,

Muse.

Schiz., 1) is not typical of

Southern

States specimens in

U.

S.

N. M. There

is a

marked

difference in the third antennal joint. Williston's figure of his St. Vincent specimen

shows

the third antennal joint

same

as the Brazilian. Beskia

and

Ocypterosipho

may

be separated on ^this character.

Genus Ocypterosipho

Townsend

Our

species

may

be

known

as Ocypterosipho eclops

Walker.

Al-

though Walker

says "palpi black,"

and

does not

mention

the slen- der

and

elongateproboscis.

Mr.

E. E. Austen's statement that celops belongs here

(Ann. Mag. N.

H., Ser. _7, vol. 19, p. 345)

must

be accepted. This is the Georgia

and Southern

States form,

and

has the third longitudinal vein bristly to small crossvein (Georgia,

Lou-

isiana,

and Texas

specimens in

U.

S. N. M.). Santo

Domingo

specimens agree with those

from

the Southern States in

having

the third antennal joint strongly

convex on under

border

and

concave

on

upper, presenting a curved outline like that of a pruning-knife blade with cutting edge

upward,

the anterior distal corner of the joint being

produced

^{in profile} into a sharply pointed prolongation.