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NO. 2192.

DRAG0NFLIE8, CALIFORNIA AND NEVADA— KENNEDY. 525

species were

common

intheAmerican River atSacramento, Kings River at Readlcy, the San Joaquin at Friant, and

Kern

River at Bakersfield,whichareallwide, shallowstreamswithbedsof drifting sand.

Apparentlythisspecies hasalong seasononthewingas Grinnell's records are from

May

to August.

On

the Chico River the few individuals I

saw

wereflyingabouta quietpoolattheheadofalong rapids and

when

not in motion were seated onsnags in the water or on the gravelly shore. Their habits seemed

much

like those of Opliiogomphus hisonwith which they were associated, except that theywere

much more wary

anddifficulttocapture. Theirlargesize, slender

abdomen and

peculiar

brown

thoraxreadily distinguish

them

inthefieldfrom anyotherwesterngomphine.

Both

theimago and

nymph

^{of this}slender, graceful speciesdiffer widelyinstmcture fromanyotherwesterngomphine.

The

anterior hamules in the malearecovered

by

wide laminae on the posterior hamules and the seminal vesicleis invaginatedonits anteriorface, which

makes

a deep hollowin which the two long filaments of the penis are coiled

when

in repose.

The

inferior appendage of the tenthsegmentisdividedtoitsbase,

making

apair of inferiorappend- ages. (Seefigs. 150-154.)

InlifeProgomphus horealisis noticeablefor thereddish

brown

of the frontof the thoraxand theyellow

abdomen

withthelargeblack triangles on segments3-8. IndetailthecolorisasfoUows:

Male.

—

^{Entire face gray but horizontal surface of frons pale}

brownish;, vertexdark brown,lighterposterior totheocelli; occiput graywith brownish tinges;eyes gray. (Ifind that Ihave omitted theliveeyecolor in

my

field notes.)

Upper

third of postoccipital regiondark brown,lower two-thirdscreamy withahorizontal

brown

stripe. (See fig. 148, A.)

Thorax with anterior surface pale

brown

and sides pearly gray.

The

followingmarkings occur:

An

obscure reddish

brown

stripeon eachside of the middorsal carina, these stripes wedgeshaped,with the wide end below; a wide reddish

brown

humeral stripe, and anterior to tliis, separated

by

a paleline, asecond widestripe, the upperendofwliichusually connectswiththeupper endofthewedge stripenextthemiddorsalcarina; a

brown

spoton the metathoracic spiracle and thesecondlateral suture brown; legswith coxaepale, femora palewith black apices and ablack stripeon theupper and posterior surface of each; tibiae and tarsi black; wings hyaline except a reddish

brown

fleck atbase which, in thecostal and sub- costal spaces, does not reach beyond the basalsubcostal crossvein.

Thereisnocolor intheorigmofthesectors ofthe arculus, asoccurs in the eastern species, Progomphus obscurus; costa yellow, ptero- stigmajet black.

526 PROCEEDINGS OF THE NATIONAL MUSEUM.

vol.52.

The abdomen

^is creamy yellow with the following intense black markings:

The

upperhalf ofsegment 1,anirregulartriangularspot on side ofsegment 2, an approximately triangularspot on theside ofeachofsegments3-7; theapex ofeach ^oftheseis at the anterior end of thesegment, and the twospots onthe oppositesides of any segment meet dorsally across the apical end; sides of segments 8-10heavilymottled withblack; superiorappendagesyellow; inferior black.

Female.

—

Coloredasis the male,but the side of segment 2 with twohorizontal blackstripesand segment10largelyyellow. (Seefig.

148, B;149.)

Five Chicomales measureasfollows

:

Abdomen,

42-44

mm.;

hind wing, 30.

Two

females from Los Angeles measure,abdomen,43

mm.,

hindwing, 33-34.

The nymph

of thisspeciesis

more

highlyspecialized forburrowing than anyotherodonate

nymph

withwhichI

am

familiar. Itisthe mostfrequentlyoccurringformoflarge insectlifefoundin thesand beds ofthe rivers ofcentral andsouthern California.

All the rivers of California originate in the mountains as swift, clearstreams, but nearly all before reaching the sea have almost levellower courses where they lose their swiftness,

become warm

and

meander

overbeds of shifting white sands. These sand beds are so unstable that they actually flowwith the water thoughata

much

slowerrate. Perhaps thisneeds further explanation.

A

good exampleisthatofthe

Kern

River at Bakersfield.

Above

the intake ofthe irrigatmg canalinthelatterpartof

summer

thisriver

was

on anaverage afootdeep and one hundredfeetwide. Itsbed

was

of pure, loosesand. This

was

formed

by

thecurrent intosandripples which faced withtheir steepslope

down

stream.

The

sand

was

in constant

movement

as the current carried sand from the upper gradualslope,

up

over thecrest ofeachripple tolet itdrop

down

the steeper downstream slope.

Where

there were eddies and ^turns thesesandripples

became

wavesinsize,being frequentlysixinches to a foot highthoughtheywereusuallylessthan6inchesinheight.

Insuchastreamthe

bottom

inchofwateristurbidwith

moving

sand.

Itisinsuch anunstableenvironmentthatProgomphusflourishes.

Only once or twice have I actually found

nymphs

in the flowing streams butin anyside channelwhere the waterhas ceased toflow thesandbed is

marked

in aU directions

by

the curvingburrowsof thesewandering nymphs.

They

burrowin thelooseupper stratum ofsandandjustdeep enoughto cover the back. Usually the tenth segment protrudes. I have traced burrow tracks that were from tentofiftyfeet long. Ifone arrived atthefreshendoftheburrow before

some

water fowl

had

found it the

nymph

would be found spasmodicallyburrowing forward. These

nymphs

could burrow as rapidlyas theaverage

nymph

canwalk. Only suchvigorandspeed

NO.2192.

DRA00NFLIE8, CALIFORNIA AND NEVADA— KENNEDY. 527

could save an insect of this sizefrom being buried in the

movmg

sand.

The nymph

of Progomphushas beendescribed

by

Dr. J.G.Need-

ham

asfollows:

^

Headdepressed,slopinganteriorly,cordate,broadlynotched behind; hindangles rounded. Antennae inserted into cylindroid elevationsonthefront,depressedand incurvedsoastoalmostsurround the pilot-shapedlabrum:twobasaljointsveryshort;

third,twice as long as thetwobasalcombined,slightlyflattenedand upcurvedatthe tip;fourthjointsmall,one-third to one-fifth \phscuriis]aslong asthethird,slender andstronglyrecurved.

Labiumrathersmall,reaching,whenfolded,tothe basesofthemiddlelegs;sub-

mentumshortened;mentumnarrowed atitsproximalend,itsmedianlobepromi- nent,rounded,fringedwitharow offlabellate scaleswhose bases are overlaidby anotherrowof shortersemicylindricalscales;beneaththis fringe,themargincut into aseries ofobscure rectangular teeth;laterallobes short,nearly straight, unarmed, roundedat apex;movable hookstout,moderatelyincurved,andtapering.

Thoraxsloping totheheadand to the basesofthe legs; prothoraxof unusual dimensions onthe dorsalside,itshind margin onlinewiththe basesofthehindlegs, being extendedbackuponthe other thoracic segments, shield shaped,witha short collarclosebehindthe head. Wing-casesstrongly divergent. Legsconspicuously fossorial,fore legsapproximatetothesides ofthe head, bearing shieldsofstiffhairs behindwhichthemiddlelegsmaybe broughtforward. Middlelegsapproximated onthe venter, rotated downwardand extended horizontallycloseunderthefore legs. Hindlegs longer, morenearly normal, directedposteriorly. Foretarsiwith solesfacinglaterally;middle tarsirotated ontibisesoas topointbackward;hind tarsielongate,the thirdsegment aboutas long asbothbasalsegments,itsclaws sharp andlong; clawsof foreand middletarsishortandblunt. Eachfemur withadistal anterior processwhichrestsagainstandsupports thetibiawhen movedbackward.

Abdomenspindle-shaped[oftscwras],segments aboutequal,theninthalittlelonger thanthe others; dorsalhooksvariable,rudimentary,moreorlesswell representedon segments2to9\_ohscurus\. Lateralspineson5 to 9 [ohscurus],on5 ratherminute.

Appendagesslender, tapering, superiorand inferiorsequal,about onethird longer thansegment10, lateralsabouthalfaslongastheothers.

The

preceding description

was

written for the eastern species, Progomphusohscurus(Rambur). IbehevethePacificcoastform to beadistinct species,soitwould havetobecalledProgomphushorealis McLachlan. It diffei-s in the imago in being larger than ohscurus andinhavingasinglerow^ofdenticlesontheinferior sideofthemale superior appendages (fig.154). Inohscurus, aspointed out

by

Cal- vert,2theposteriorendof thisrowisdouble ortreble.

Ihave quoted thedescription of ohscurusfrom

Needham

and have figuredthehorealis

nymph

to

show

that thedifferences betweenthe twospeciesare

more

conspicuousinthe

nymph

thanintheadult. (See figs. 155-163.)

The

specific characters of the horealis

nymph may

be given as follows

:

Lengthshorterthanthatofohscurus

nymph

andv/idthgreatersothat thehorealis

nymph

hasnoneoftheappearanceofextremeslendernessas

1NeedhamandHart.,Bull.111.StateLab. Nat.Hist., vol.6,art.1,1901, pp. 55-56.

«Biol.Cent.Amer., Neur.,p. 149.