96 MPTERA OF NORTH AMERICA. [PART IV

the

middle

of the stigma,

and

hence nearer the tipof the first

longitudinal veinthanin thepreceding^species.

Hah.

Illinois (Kennicott) ; a single female.

The

feet are

wanting and

the

thorax

^is

somewhat

injured

by

the pin;

but

the speciescan never be

mistaken

for

any

other.

The

followingspecies

from

California has not

been

included in thedichotomical table

on page

8T ^:

—

lO.

L,.

californica

^0.S. %^.

—

Thoracis vittisquatuorfuscis; alis fuscesceutibus, pallidefenestratis,margineauticomaculis quatuorfuscis.

Thoraxwithfour brownstripes; wings brownish, with some subhyaline spaces; anteriormarginwithfourbrownspots. Long. corp. 0.7

—

^0.8.

Syn. Limnobiacalifornica 0. Sacken, Proc.Ac.Nat.Sc.Phil. 1861,p. 288.

Front and

vertex

brown

;

under

side of the

head

yellow

;

rostrum, palpi,

and

antennae

brown

;

two

basaljoints ofthelatter yellow.

Thorax

yellowish,

mixed

with

brown

; the

two

inter-

mediate

thoracic stripes are narrow, ^parallel; at their anterior end, they coalesce with the

brown margin

of the

mesonotum, which

^is broadest at the

humeri

_; pleurse, scutellum,

and meta-

thorax

more

or less tinged with

brownish

; basis

and

tip of the halterespale,the intermediate portion infuscated;

femora brown-

ish; a yellow

band

before the tip,

which

isblack; tibite ferrugi- nous-brownish,

brown

at the.tip; tarsiferruginous-brownish at the basis,the

remainder

brown.

Wings with

a uniform

brownish

tinge; four large

brown

spots

along

the anterior

margin

; the

firstat the inner

end

ofthe firstbasal ^cell; the second,

somewhat

trapezoidal in shape, at the origin of the prsefurca;

both do

not cross the firstlongitudinalvein,

and do

not, therefore, reach the anterior

margin

; the second is limited posteriorly

by

the fourth longitudinal vein; the third spot is double, consisting of

an

oblique spot

which

begins at the margin,just

beyond

the tip of the auxiliary vein

and

coalesces with a

round

spot atthe inner

end

of the

submarginal

cell; thefourth spot isat the tip of the first longitudinal vein; it is semi-oval

and

is inclosed

between

the costa

and

the second longitudinal vein; there are several subhyaline spots

on

the surfaceofthe

wing

; a large angular one, beginning

about

the middle of the anal cell

and

reaching _the

TROCIIOBOLA. 9T posterior

margin

at the tip of the seventh longitudinal vein; in the second basal cell(near t]je great cross-vein); inthe discal cell; atthe tipof the

wing and on

both sidesof the fourth

brown

spot^; a subhyaline longitudinal streak crosses the second

brown

spotin the first basal cell

and

the

round

spotat the inner

end

ofthesubmarginalcell is encircled in pale.

The

subcostal cross- vein is almostin one line

with

thetip of the auxiliary vein.

Hah.

California (Mr. Alex. Agassiz).

A

^single male.

This

species belongs to the relationship ofL. cinctipes

and immatura,

but is easily distinguished

by

its larger size

and by

its

brownish

wings,

marked

with subhyalinespots.

Gen. V.

TROCHOBOLA.

Onesubmarginalcell; fonr posteriorcells; a discalcell; thetipof the auxiliaryveinisfar beyond the origin of the second longitudinalvein

;

the marginal cross-vein is some distance anterior to the tipof thefirst longitudinal vein; asupernumerarycross-vein connectsthesixth and seventh longitudinalveins(wing,Tab.I,fig.4). Antennae14-jointed. Feetslender;

tibiaewithout spursatthetip; empodia indistinct; ungueswith teethon theunderside.

Trochohola

is

most

closely allied to the

Limnobise

of the second

group

(those with the

marginal

cross-vein

removed

from the tip of the first longitudinal vein); like these species, it has pictured wings,

brown bands on

the femora, a long auxiliary vein, etc.

But

it is easily distinguished from

them by

the presence of a

supernumerary

cross-veiu.

The

antennae

have

less elongated joints,

and

look almost moniliform; thefeetare

more

slender than in the majorityof the

Limnobise

; the structure of the

male

forceps is

somewhat

intermediate

between Limnobia and Dicranomyia

; the fleshy lobes of the latter are

somewhat

reduced in size here

and

the rostriform

appendage

is

compara-

tively larger.

(A

figure of this forceps hasbeen given

by me

in the Stett.

Eniom.

Zeitschr. 1854, Tab. I, fig. 1^{; it} representsthe forceps of the

European

T.

annulata

Lin.)

The number

of species belonging to this genus issmall, they

have

a

remarkable

distribution all over the world,

and

theyall (as faras

known) have

the

same

eye-like spotson the wings. T.

annulata

Lin. (imperialis

Lw.) and

T. caesarea 0. S. (perhaps only a variety of the former), occur in northern Europe. T.

argus

Say, is almost identical with the former. ^. I have ^seen, iu 7 July,1868.

98 DIPTERA

OF

NORTH

A>rERICA.

[PART

IV.

the British

Museum, numerous

specimens of

Trochobola from

New

^Holland,

Van Piemen's Land, and New

^Zealand,

showing

that theyarequite

common

there;

one

ofthem,

marked Limnohia

tessellata White,

which

I examined,

showed

precisely the

same

distribution ofthe spots

on

the

wings

as T.imperialisor

argus

_; Idid not notice,

however, whether

the otherspecimens

belonged

to the

same

^species ornot.

In

the Proc. Philad.

Entomol.

Soc. 186.5, p. 226, I

had

pro-

posed

for this

group

the

name

of Discohola, which, being pre- occupied, is replaced here

by Trochobola

(fromrpoxoj, a wheel,

and

j3axxw,I throw).

1>

T. argus

Say.

%

and 9^.

—

Fuscano-flavida; alisfuscoocellatis.

Brownish-yellow, wings withocellatebrownspots (Tab.I, fig.4). Long.

Corp.0.25—0.3.

Syn. Limnohia argus Say, Long's Exped. Append, p. 358.

—

Wiedemann, Auss. Zw. I, p. 33,

17.—

0- Sacken, Proc. Ac. Nat. Sc. PhiL 1859,p. 217.

Head,

rostrum, palpi,

and antenn®

black; thorax yellowish

with

three

brown

stripes

above

; theintermediate double_; pleurae with

two brown

^stripes; halteres with a

brown band

acrossthe

stem; knob

likewise

brown; abdomen

brownish, genitals paler;

feetyellowish;

femora

with a

brown band

at

some

distance

from

the tip^ tipof the tibiifi

and

last joints of the tarsi infuscated.

Wings

yellowish or whitish,with brown,ocellate spots especially along the anterior

and

posterior

margins

; the centre of these spots, forming thepupil of the eye, is likewiseinfuscated; these centres are mostly placed at the origin or atthe tip of the longi- tudinalveins, or

upon

cross-veins: thus a complete ocellus has the origin ofthe prtefurca foritscentre ; a

double

one surrounds, as centres, the inner

end

of the

submarginal

cell

and

the small cross-vein; other centres of less

complete

ocelli are the tip of the seventh longitudinal vein

and

the

supernumerary

cross-vein, existing there; likewise thetipofthe sixth vein

and

theinner

end

of the fifth basal cell; the apical portion of the

wing

contains several

more

ocelli,

more

or less distinctly

marked

in different

specimens and

giving that portion of the

wing

a variegated appearance.

Mah. Northwestern

Territory (Say);

Nova

Scotia (British

TROCIIOBOLA. 99

Museum)

;

Trenton

Falls, jS".

Y.

;

Maine (Packard)

;

Massa-

chusetts (Scudder); Orange,

N. Y.

This species is

somewhat

variable inits size, the intensity of the coloring,

and

the distinctness of the spots

on

the wings. I possess a

specimen from Fort Simpson, H.

B. T. (Kennicott),

which

is altogether

brownish

; the thorax is brown,

somewhat

yellowishsericeous above,

without any

apparentstripes; halteres brownish, pale atthe basis only; the ocellate spotson the

wings

arethe

same

as usual, but

much

darker

and somewhat

broader, thus imparting a darkercoloring to the

whole

wing.

The Euro- pean

T.

annulaia

Lin. (imperialis

Loew,

Lin)}.

Entom. V,

p.

103,

Tab.

II, fig. 14-15) ^is hardly

more

distinctfrom T. argus,

than some

of the varieties of the latter are one

from

another.

A

closer observation will haveto teach us

what

to

make

of these modifications of the

same

typicalform.