THE NYMPHS OF WESTERN GOMPHUS

568 PROCEEDINGS OF THE NATIONAL MUSEUM

13. THE NYMPHS OF WESTERN GOMPHUS

The

following characterization of the

nymphs

ofGompJius isfrom Doctor Needham's Aquatic Insects in the Adirondacks _(pp. 435- 436and443)^:'

Middlelegsnotmore approximate thanfore legsat base,the fourthsegmentofthe antennaamererudiment,muchshorterthanthe thirdsegmentiswide; tenthabdomi- nalsegmentmuchshorterthanninth. Wingcaseslaidcloselyparallelalong the back;

laterallobeoflabium endingina sharp, incurvedhook. Abdomenonly slightly depressed,ovatetolanceolateinoutline,atleasttwice as long as wide. Thirdjoint ofantenna elongate, linear, little flattened. Dorsumofninthabdominal segment rounded,orwitha low, obtusemedianlongitudinalridge.

GOMPHUSINTRICATUS,nymph.

A

thin skinned,whitish exuviawith sooty tints onthe

abdomen;

moderatelyslender. Sm-facevery sparsely coated with exceedingly minute bristle-likehau's. This is a typical Stylurus

nymph

and is

distinguished

by

the followingcharacters:

Mentum

^of labium transparent, tapering proximad with sinuate sides,widthofposteriormargin one andthree-fourthstimes inthat ofanterior

margm.

Middle lobe convex, with afringe of about 60 bristlelikescales.

Each

laterallobebroadat base,withacrescentic tipthatissuddenlycontractedto alargeterminal pointstandingat rightanglestothelobe;three largeand twosmallerroundedteethon theconcaveedgeposterior tothe termmal point. Burrowing hooks rudimentary on both first and second tibiae.

Wing

pads reaching tosegment4.

Abdomen

lanceolate,veryslightlycontracted atbase ofsegment 9,subcircularin cross section.

A

dorsal grooveonseg- ments 3-7.

No

middorsal hooks or spmes. Segments 6-9 with lateralhooks, those on 9 one-half the length of segment 10. Seg- ments 2-9 subequal in length; segment 10 one-third the length of segment9, and twice aswide as long. Appendagestwicelength of 10. (Seefigs.315 and321-323.)

Length, 27

mm.; abdomen

(includingappendages),19;hind femur, 4.

Width

ofhead,5

mm.

;abdomen,6.

Describedfrom4 female

nymphs

collected onthe

Humboldt

River at Lovelocks, Nevada, August 10, 1914. These were taken from dead

weed

stems 2feet abovethelowestlevel ofthe river.

At

this point

was

adeep hole (3 feet) with a

muddy

bottom, the greatest partt)ftheriver bed

bemg

composed of a coarsegrit.

GOMPHUSOLIVACEUS NEVADENSIS.^nymph.

A

^large,slender,whitish exuvia, sparsely covered with minute bristlehke hairs. This is a typical Stylurus

nymph

and is distin- guished

by

the followingcharacters:

»BuU.47,N.Y.StateMus.,1901.

2Aformof olivaceusnymphhas been describedbyNeedhamfromSeattle,Washington,as sobrinut inProc.U.S.Nat. Mus.,vol. 27, 1904, p. 692.

DuringAugust,1915, 1found thesameformofolivaceusontheOwensRiver,InyoCounty,California, asthatfoundatSacramento,whichisthetypical olivaceus. ThenymphsoftheOwensRiverolivaceus wereidenticalwith thoseofOompliusolivaceusnevademis.

NO. 2192.

DRA

^00NFLIE8,

^CALIFORNIA AND NEVADA-KENyEDY.

⁵⁷¹

Mentum

translucent,itswidth one andtwo-fifths inits length; sides of anteriorportionsubparallelandquickly contracted

by

a shortsmu-

%^'

Fig. 314.—Gomphusolivaceus nevadensis,nymph.

Fig. 315.—Gomphusintricatus,nymph.

Fig. 316.—Gomphusdonneri,nymph.

Fig. 317.—Gomphussobrinus, ny-mph.

ot posterior end one and ^{a half to} one and three-fouiths times

572

PROCEEDINGS OF THE NATIONAL MUSEUM.

vol. 52.

in thatof anterior end; middle lobe convex, with 30-35 bristloliko scales; eachlateral lobewitha cresentictip turnedinward at right angles; on the concave edge 3-4 large rounded teeth. Burrowing hooks rudimentary on bothfirstand secondtibiae.

Wing

padsreach- ingsegment4.

Abdomen

lanceolate,taperingregularly,subcircular in cross section.

A

dorsalgrooveon segments3-7.

A

minute mid- dorsalspineon apexofsegment9. Lateral hookson segments6-9, those on9 reachingtobaseof10. Segments 3-8subequal;segment 9one and a halftimes the lengthof8; segment10 three-fifthslength of8. Appendagesequalto 10. (See figures314and 318-320.)

Length, 38

mm.;

abdomen,26; hind femur, 5.5.

Width

of head, 6

mm.;

abdomen,7.

Described from 6 exuviae collected on the

Humbolt

River at Golconda,Nevada, August 9, 1914.

The

river at this point flows through an alkaline, salt-grass flat.

As

it meanders it undermines

tlie saltgrass sodwhich cavesinto the edge of thestream in large squares. Itwas onthese sods that theexuviaewerefound.

GOMPHUSSOBRINUS,nymph.

A

^heavy thick-skimied exuvia usually thickly coated with

mud

because^{of a}dense coatofvery short spinyhau"s,differingnoticeably in thisregardfromdonneri exuviae,which have fewhau-s andthese usually very clean. General shape intermediate, neither short nor slender.

Abdomen much

less arched than indonneri. It is distin- guished

by

the following characters:

Mentum

of labium slightly longerthanwide,its posterior edge three-fifths to two-thirdswidth of anterior edge, its sides instead of being sinuate suddenly con- tracted proximad,

making

asharp angle or "step" on either side.

(Asmall percentageof the specimensisintermediatein thismental character,the"step" of thesidebeing

more

sinuous.) Middle lobe of

mentum

convex and fringed with about thirty bristle-like scales. Lateral lobes broad at base,tapering regularly to a cres- centic tip,the inner margin ofwhich bears 7-9 lowroundedteeth, followed

by

smallerones towardthe base of the lobe. Welldevel- oped burrowing hooks on both firstand second tibiae.

Wing

pads reaching middle of segment 4.

Abdomen

lanceolate, slightly con- tracted atbase of segment 9, only moderately arched, its ventral surface

much

flatterthanin donneri.

No

dorsal groove,butapexof segments 2-7 with a low rounded middorsal tubercle.

A

^minute

middorsal tooth, hardly discernible, as it is concealed in a tuft of hairson apexofsegments2-7,largeron segments 8and9. Lateral hookson segments6-9, those on segment 9one-third thelength of 10. Segments 2-8 subequal in length. Segment 9 one andahalf times the length of 8; segment 10 two-thirds the length of 8.

Appendagesequalto10. (Seefigs.317 and326-328.)

Length, 38

mm.;

abdomen,26; hind femur,5.5.

Width

of head, 6

mm.;

abdomen,7.

NO. 2192.

DRAG0NFL1E8. CALIFORNIA AND NEVADA - KENNEDY.

573 Thisspeciesdiffersfromdonneriinthesides ofthe

mentum

bein- angulated, _inthe heavier skinned character_{of the}exuviaandin the dense coatofminute, spinyhairs.

320

323

riGS..318-320.-GOMPOTS^OUVACEUS NEVABENSIS, N.^MPH. 318.MENTUM. 319.MenTAL LOBE. 320.

Figs.321-323.—Gomphusintricatus.

I'iGs.324-325.—Gomphusdonneei.

Figs.326-32S.-Gompiius sobeinus.

Describedfrom exuviae coUected

May

31, 1914, on CoyoteCreek, ban Jose, Cahfornia, where the exuviae were numerous along the

mud

banksofthe stream.

574

PROCEEDINGS OF THE NATIONAL MUSEUM.

vol.52.

GOMPHUSDONNERI,nymph.

A

^{lightcolored,} verydelicatoand thinskimied exuvia,itssurface thinlycovered withveryshort,spinyhairs. Generalshapeinterme- diate, neither broad nor slender. It is distinguished from other GompTius

nymphs by

the following characters

:

Mentum

oflabiumslightlylongerthanwide,itsposterioredgetwo- thirdswidthof anterioredge,its sides slightly sinuate. Itsmiddle lobe convex, with a fringe of about 30 bristlehke scales. Lateral lobes broadatbase,tapering regularlyto acrescentic tip,the inner marginofwhichbears about7lowroundedteethbetween which and thebaseof the lobeareother smallerteeth. Welldevelopedburrow- inghookson boththefirstandsecondtibiae.

Wing

padsreachingto or beyond apex of third segment.

Abdomen

lanceolate, slightly contractedatbaseofninthsegment,wellarched,nosign of adorsal groove, but apex of segments 2-7 with a low rounded middorsal tubercleterminatingcaudadinaminutemiddorsal toothon apexof segments2-7, larger on segments 8 and 9. Lateral hooks on seg- ments6-9, thoseon9 one-fourth toone-third the lengthof segment

10. Segments 2-8 subequal in length; segment 9 one and a half timesaslong_{as 8;} segment10aslongasbroadandtwo-thirds length of 8. Appendagesaslong as segment 10. (See figs. 316 and 324- 325.)

Length,29

mm.;

abdomen, 20; hind femur, 6.

Width

of head, 5

mm,;

abdomen,6.5.

Described from 2 male and 1 female exuvia and 6 fragmentary exuviae collected onthe westend of

Domier

Lake, California, July 24, 1914. These were found in the trash of the

wave

line on the sandybeaches along the northwest pointofthelake.