42 DIPTERA OF NORTH AMERICA.* [PART IV

marginal cell

have

four posteriorcells,

and

there is only one ex- ceptionto thisrule:

Cylindrotoma

didinctissima

and

itsvicarious

North American

form

—

G.

Americana

;

Meigen's

figurerepresents the

wing

of the former. Therefore

Mr. Walker's

description

must

eitherreferto

some

species entirely

unknown

tome,or

more

pro- bably, the statement about its

wings

being like

Meigcn,

Tab.

Y,

fig, 5,

must

be erroneous.

Moreover,

the

name

L. turpiscannot be retained, as

Mr. Walker

himself has described another L.

turpis in the Insecta Britannica, Diptera, Vol. Ill, p. 300, in the

same

year 1856.

The

description is givenin the

Appendix

to this volume.

23.

Limnobiorhynchus

canadensis

Westw. = Geranomyia

canadensis

(comp.

below),

24.

Anisomera

longicornis

Walk. = Eriocera

longicornis (comp. below).

25.

Chionea

asjjera

Walk. = Chionea

valga Harris (comp.

below).

26.

Chionea

scita

Walk.

;

unknown

to

me

; the description is

reproduced ⁱⁿ the

Appendix.

27.

Chionea

valga Harris, described

below under

the

same name.

2S.TrichocerabimacuIa Walk.

[

^h^

descriptions of the..e 29. Trichoceragracilis \Ya\k. ^!

somewhat

doubtfulspecies 30. Trichocera

brumahs

Fitch. ^{< ^^'^}

reproduced

inthe

Ap-

31. Trichocera scutellata Say.

pendixl

_;

compare

alsothe

[

genus

Trichocera.

32. Trichocera

macuUpennis

Meig.^; a

European

speciessaid to occurin Greenland, accordingto Stceger.

33. Trichocera regelatioms Lin. ; also a

European

species,

quoted by

Otto Fabricius, as occurring in Greenland,

which

requires confirmation.

34. Gynoplistia

annulata Westw.

I

have

seen the original

specimen

in

Mr. Hope's

collection at Oxford,

and have

never

met

with any other,

Mr, Westwood's

description is

reproduced

in

Appendix

I.

35.

Bittacomorpha davipes

is described

below under

the

same name,

36. 3t.

Ptychoptera

metallica

Walk, and

quadrifasciafa

Say

are

unknown

to

me

; their descriptions will be found in the

Appendix,

INTRODUCTION. 43

Since the publication of

my

Calalofjue, etc., a

Limnobia

nigri- cola

Walk,

has

been

described iu the Trans.

Loud. Entom.

Hoc.

Y, N.

S. pt.

YII,

p. 66. It is apparently

my Gnophomyia

luctuosa.

The

^result of the foregoing examination isthefollowing:

—

Omitting

thesixspecies of the

genus

IVichocera, whichrecjuires anentire revision,elevenspecies,

among

the thirty-two

which have been

described,

have

not

been

identified; of these six or seven, because they

have

not been

among

the

number

of species

which

I

have had

for examination:

Limnophila

carbonaria

Macq.

_; Gynoplistia

annul

ata

Westw.

;

Bhypholophus

fascipennisZett._;

Limnobia

gracilis

Wied.

; PtycJioptera quadrifasciata

Say and

vietallica

Walk.

;

Chionea

sella

Walker may perhaps

be

added

to the

number. The

four remaining species {L. hiimeralis Say, biterminata, ignobilis,

and

turptis

Walker) have

not

been

iden- tified

on

account of the insufiiciency of the descriptions.

44

riPTERA

OF

NORTH AMERICA. [PART

IV.

TABLE FOR DETERMINING THE GENERA.'

TTwo

longitudinal veins between the fifth vein and the posterior

, ! margin. ²

I

Onlyone longitudinalvein between the fifthvein and the posterior L margin;Tab. II,fig.19and20(Sect. VIII. Ptychopterina). 45 Last jointof the palpi shorter ornot

much

longer thanthe twopre- cedingjoints taken together; the auxiliary vein usuallyends in the costa,and is connected with the first longitudinal vein

bya cross-vein. 3

Lastjointof the palpi verylong,whiplash-shaped,

much

^longerthan the threeprecedingjointstakentogether;the auxiliary veinends in the firstlongitudinalvein; nocross-veinbetweenitandeither of thetwoveinsrunning alongsideof it(Tipulida longipalpi).

o (

A

singlesubmarginalcell;2 Tab.I,fig.1-13. 4

\

Two

submarginalcells;»Tab. I,fig. 14-20,andTab. II, fig.1-18. 6

' This table contains all the

known

European and North American generaof the eightfirstsections ofthe TipuUdie; thetable forthe follow- ing sections (^Tip. longipalpi) will be appended to the volume treating ofthem. In using dichotomical tablesitshould always beremembered thatto construct them ⁱⁿ sucha

way

as tomeetall cases,toinclude all the anomalous structures,isimpossible,and ifitwerepossible,itwould be onlythrough theuseofanatomicalcharacters,whichwoulddefeatthe.

object in view, thefacilityofdetermination. Thus,if,in order toaccommo- date Chionea,

we

had abstainedfrom theuseof anycharacter connected withthe wings,

we

wouldperhaps have rendered the tablemore precise, but certainlyless useful. As itis, Chionea, althoughwingless,isplaced

among

the generaprovidedwith twosubmarginalcells,whereitbelongs.

Theseimperfections of the dichotomical tables occur especially in those portionsof

them

whichrefer tothe larger divisions;as soon as thegenera and species are reached,more precision can be expected,although even thereitcan never beabsolute.

2 Toxorrhinahasnoneatall.

' Cladolipeshas onlya single submarginal cell,although it belongsto this division.

TABLE FOR DETERMINING THE GENERA.

45

/•Antemiw 14-(sometimes apparently15-) joiuted (Section I.

Limno-

4J bina). 9

'Antennae16-jointe(i.' 5

fThe firstlongitudinal vein ends in the costa; tibisewithoutspurs at

I thetip (SectionII.

Limnobiua

anomala). 13

5\ The first longitudinal vein is usually incurved towards the second andendsin it; tibiae always with spurs at thetip(Section Vll.

L Cylindrotomina). ⁴³

^ ^(Tibiyewithout spurs atthetip(SectionIII. Eriopterina). 22

(Tibiae withspurs at the tip.^ 7

rSubcostalcross-vein posteriorto the origin of thesecondlongitudinal -

J vein. 8

I

Subcostalcross-vein anterior to the originof the secondlongitudinal

I, vein; Tab. II,fig. 14-18 (Section VI.

Amalopina).

38

„(

Antennse16-jointed (Section IV. Limnophilina). 32

(Antennaefrom 6- to10-jointed (SectionV.

Anisomerina).

³⁵