34{THEGENUS SIGMATOMERAWITHOBSERVATIONSON
BY RAYMOND

OSTEN
SACKEN
THE BIOLOGY
C. SHANNON.

By Cnlnr,us p. Alnxlnnnn, Amherst,Mass.(1)considering the large size of the flies and the wide distributiono{ the genus throughout Tropical America, the literature
concerning
the genus sigmatomerais surprisingly limited. Likewise
our knowledge of the immature stagesof any member of this genus
has beenvery restrioted.
I have reoently received from my friend, Mr. Raymond C.
Shan_-ofnon' an adult female belonging to a new species sigmatomera,
togother with some surprising observations on the larialhabits.
I take groat pleasure in describing this beautiful crane-fly
as Jign?,a'tomera
shannonianaand am especiallygrateful for the opportunityof retaining the type. At this same time, I take the qpporiunity
ofdescribinga secondnew speciesof this genus based on materiar
fromcosta Rica. To this speciesI have given the namesigmatomerasiguyi,
as a slight expressionof gratitude to my colleague,M. Eugdne s6dy;.for many kind favors in the past.
HISTORICAL
Thegenus Sigmatomerawas proposed by Osten Sacken (tg6g) (2)wltlout a type-species,this latter being supplied by the sameauthor-s.
(1873)with the description of the genotype,ftavipennes,of Mexico.
A second speciegS. amazonicu,was describedfrom Bralil bvWest_wood (1881).The third and fourth specieswere des*ibed by Alexander(19L4 a, L9l'4b), as s. apicarzsfrom British Guiana *rris. occultafrom Paraguay. The allotype femaro of s. amazonicafromthe Amazonian region of Brazil was described by Alexander (1920).
RiedelIIir ' contribution from the EntomologicalLaboratory,Massachuserts
Agricurtural f,orlege , Amh erst,Mass.,U. S. A.
refer to the Bibliograrohy
at end of paper.
,"g. Datesin parenthesis

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2P' AL EXAN D E R

anrl fur(Lg2L\ recorded S. occrzlta(as flavipennis) from Paraguay
to thekeys
nished the first indication of the larval habitat. Earlier(1921)'
Riedelknown specieswere suppliedby Alexander(19{4 a) andto be desare
species
additional
twoAs stated in the introduction,
by Mr'
saltmitted
shannoniana
cribed herewith. The type female of S'larvae
threeandskinShannon was accomp"niua ny the cast pupalandstudyfor
which will be submiited to ProfessorJ. Speed Rogers
report.
AFFTNITIES
tribe ErioThe genus Sigmatonterahas always been placedin thethe genus
pterini. More recently (Alexand'er,L927),I have placed
only thc
in the subtribe Gonomyaria,as a limited group containing
Austrolimnobia
andEdrvards
three genera. Sigmatoinera,Astelobia
Astelobia,
Alexan-der.The closcstally of Sigmatomerais undoubted|ypupae'anda fact that is con{irmed by the structure of the larvae
description
insofar as this can be decidedfrom the figuresand brief
apparent
increasingly
becomeItliasof the latter (Hudson, 1920).
approach
thatfeatures
many
that the Hexatomoid Eriopterini shox'of thc
various rnembersof the tribe Hexatomini and the separation
highlv
isspurs
two tribes on the basisof presenceor absenceof tibial
oI Sigmatn'
artificial. The discoveryby Sttannonthat the early stages
members
knou'nmostoffeature
predacious,a characteristic
n1,er&'areEriopfor
theknorvn
notbutof the tribes Pediciini and Hexatomini,
intribes
positionterini, has again opened the question of the strictof these higher Eriopterine crane-flies'
Sigmatomero-uyreadilybetoldfromAstelobialrythefollowing
charactersof the adult flies :l.Ante nn alSe gm ent s of bot hs ex es s t r ongly bi n o d o s c ; t e r g a l v a l r . r . s o f o r . i p ositor t r ident at eat t ips . Sign. at on. t er r r o s t c n S a c k t - n .
of ovipositor simAntennal segments of boitr scxes simple ; l,ergal valves
Astelobia Edrvards'
ple . . .

TAXONOMY
Thesixknownspeciesof.sigmatomeraatebeforemeandtlrerange
in structure of various organs may be briefly noted'
being reduced
Eyes very large in boih se*es,the anterior vertex
in female ;thanmalcinto a nanow strip. Antennae slightly longer
in bothnodoset)
basal anrl intermediate flagellar segments (fig'T H E GENUS SIGM AT OM ERA

OST E N S A C K E N

3sexes;.basal flagellar segmentelongate,with only an apical node I
succeedingsegmentswith the ventral face hinodose; dorsal face atbase Iikewise strongly protuberant; nodes of ventral face provided
rvith two or three short, setae; on dorsal face of segmentsthe setae
are more elongate,especiallyon the basal segments,there being twolong bristleson the basal node and a singlebristle near the.constricteJpart of the segment; outer flagellar segmentsless constricted,theterminal segmentsmall, oval; antennae lvith t6 segments, aPParently with onIY t5 in J. amazo'knica. All legs long and slender.
/,/
Venation : .9crand Rr+z approxi//mated on costal margin ; l?sarcuatedgentlystraight i Jlz+iJ;i(apicalis,amazonica),weaklY anFig.2
gulated, to stronglY angulated
and spurred (occulta); r-m coti'tsasal l i ve segments of l l aF is. l. necting with .Rs before the fork g e llu in o f S i X mutomera sl rtnnoni ana, sp'n. I female.
of the latter (occulta),aL the fork
F is. 2 . - A pex of [ergal val ve of ovi (seguyi, shannoniana) or beYond p o sit"o r u f S i rl mrtl omer,trrm,rzorri cuWes[wo o d .
the fork on ,R5;cell tsl l4z closed
or open by atrophy of.m (amazonica); m usually short and straight, in many caseswith a short spur
jutting basadinto cell I st M r; anterior cord nearly transverse(fla7ishannoniana);
to stronglyoblique(occwlta,pennisl arnazonica,segwyi)
rn-cu aLorbefore(shannoniana)or shortly beyond the fork of ,41.The
venation of these speciesis shown in text-figures 3-8. Ovipositor withthe tergal valves expandedand weakly tridentate at tips (fig. 2)'KEY TO THE SPECIESO}' SIG\TATONIERA
t . CellL stM2 op en ;t hor ax blac k . ( f ig. 3) ( Br az il) . . . an t , a z o r r i c a We s t r r 'o o d
2CeIl I sl ,M, ciosed ; thorax yellowish
forkofbeloredistance
somc
trl-cuincell"R,;
2. l\ supernumerary crossvein
shartnorriarta'sp' L'
M. $t'g. a) (Brazil)
the fork ol M'3
beyondorat
r\o supernumerary crossveinin cell R5; m-cu
3.Wing swith ab rokendus k y c r os s bandnear bas ean d l r 'i t h a p e x b r o a d l y d a r .
apicalis Alexander
kenecl (Iig. 5) (British Guiana)rrWings without darkening at base and apex
yellowhrightof;
exception
thewithol
cord,-Rs,
4. veins of tvings proximad(Costa Rica) '." " '6)(lig'cord'along
mossbandbrown
dark
distinctasp. nr. . . ,segz{.yrCHARL ES

Certains

veins ofwing

P. AL EXA N D E R

proximadof cord, including

Cuand, 2nd, A,

blac-kened .
5
5. Wings with a pale yellow ground-color, the base and costal region a littlebrighter; cord very oblique, the inner end of cell L st M, pointed; darkcoloration of wings virtually confined to the veins ; legs yellow, the tipsof the tibiae and outer tarsal segments infuscated (fiS. 7) (Paraguay).

brighterr.ll;;,';;;
Wingswith the ground-color;;*'"T;":f#iilJt::;

bright yellow; cord transverse, with a narrow dark seam that includes
the adjoining membrane as lvcll as the veins ; legs clcar yellow, including
the tarsi. (fig. S) (Mexico)
flaoipennis Osten Sacken.

Fig. 3. Fig. 1, Fig. 5. :Fig. 6. Fig. 7. Fig. 8. -i3igmatomera

Sigmatomera amazonica Westwood I venatioD.
Sigmatomeru slnnnoniana, sp. n. ; venation.
Sigmatomera apicalis Alexander ; venation.
Sigmatomera seguyr', sp. n. ; venalion,Sigmatomera occulta Alexander; venation.
Sigmatomera llaaipennis Osten Sacken ; vcnation.

shannoniana,

sp. rl.

General coloration reddish yellow ; legs orange-yellow,the tips ofI he tibiae and the tarsi light brown ; wings yellow, the baseand costal
I egion more orange-yellow; veins chiefly black ; a supernumerary(irossveinin cell R"1m-at, beforethe fork of lf.
Female.- Length about 18 mm. ; wing, tb,b mm.
Rostrum reddish brown; palpi yellow. Antennae with the basal

T T I E GENT IS SIG} IAT ( ]IIERAOST E N S A C K E ry

5segmentreddish brorvn, the remainderbrack.
Head testaceousyellow ;anterior vertex verv narrow, at narrowest point
about equar to onefourth the diameter of the basal segmentof scape.
Mesonotum chiefly obscureg".*irh yellow,
the color more or lessobscuredby internar discororationshowing throughthe chitin. preura
reddish yellow. Haltere.syellow. Legs orange_yellow,
the tips of thetibiae infuscated; tarsi similarry dirkened,
the coloration in rarge
part due to dark setae.wings (fig.
4) yelrow, the base and costal
region more orange-yellow; veins black, thecoloration invorving theveins and slight extensions on to the membrane; prearcular veins,c,sc,R,Rr, basalhalfof M and rsl.4 yellow.venaiion:Asupernumerary crossvein in cell .R3 at near midlength
I Rz+;t+tangulated
and short-spurrednear midrength; r-m at forkof .Bs; m witha shorl
spur into cell I st M , ; m-cwnearry its own length
before tr'tefork of M;
inner end of cell L st M 2pointed cord unusuallyoblique.
;
Abdomen reddish yelrow, clear yellow at base.
ovip'sitor trark
reddish brown, the tergal valves tridentate attips, ,rsin genus.
Hab. Brazil.
Holotype, t, Bahia, April 1g29,emergedas adult
July 3, 192g,rea,from larvae living_intree-holes(N."c.Dauis arul
R. c. shannon).
'edType preservedin lhe author,s collectjon.
I t-1ke great pleasure in naming this speciesin honorof rny friend,- - Raymond[4r'c. Shannon.The speciesis most closely related to Jlgnlatonxeraocculta Alexander.
Sigmatomera

s6guyi,sp. rr.

General coloration yellow ; legs yellow, the tips ofthe tibiae ancl
the tarsal segmentsbrown ; wings yeilow, with aconspicuousbrowncrossbandalongthe cord; veins basadof cord, withthe singleexception of .Rs,bright ;rellow cord nearly transverseI; *_ri shortly
beyond the fork of r]f.
Female.- Length about t6-I7 mm.; wing tb_16,5mm.
Antennae with both segmentsof scapey"ilo*, the flagenurn
biack.
Thorax reddish yeilow. Halteres yrho*. Legs yelloi,
the tibiac
passinginto brown at tips, the tarsi chiefly darklrown.
Tie horotype
shows two distinct brown rings on all femora, thefirst before midlength, the second.subterminarin position theseareas are not indi;cated on the paratypes. wings (fig. 6) bright yeilorv
rvith a narrow
but conspicuousbrown crossbandalong the cortr;
veins basad of thecor"d,with the exception of fts, entirely bright y.llo*;veins beyond
fhe cord a little darkened. Venation : Rr+r+r-arcuated ," *r'"i.f;CHARL ES P. AL EX.\N D E R

fork ol M ;angulated h:fore midlength ; tn-cu shortly beyond thecord nearly transverse'
I/ab. CostaRica.
lIolotype,g, May 16, 1920(l)uuL Serre)'
2 broken females'
ParatopotuPes,
Type in tle Natluttul X{useumof Natural History, Paris'x't. EuTLis beautiful sigmatomerais dedicated to my colleague,Osten
gdne S6guy. The speciesis most closely allied to S' flavipert'nls
Sacken.
BIOLOGY
by Riedel (1921)
The first indication of the larval habitat was given
whenhediscussedthemateria|o|signmto|nercloccwlta(reoordedas
These notes
S. flavipennls)that r'vastaken in t9t4-tb by Zilrcher'regiu'Poinciana
are as follows : < Larvae in tree-holes,principally
6'L9L4;
November
Forest,larvaefrom a tree-hole'
October 13,1.91'4;
fromLarvae from tree-holes,- the large yellorv larvae transformed
mid-April to the end of MaY ''Shannon are
The interesting notes supplied at this time by Mr'
as follows :thema 'fhe larvae occur in the rot holes of trees and we foundexaminationforby collectingthe rvater from tree-holesin a routine
aegypti (Linnmus)
the larvae of the yellorv lever mosqrtito, Aed'es
that theselaboratory
thein(Stegomyia).W" qoirt ly discovered
crane-flylarvaearepredaciousandinthecourseofrearingapproximalarvae'
Stegomut'ately trventy larvae, tlese latter consumedabout 2500
alsomustbutThLy probably never obtain this number in nature'
feedonNematodesandotherinsectlarvaethatinliabitthetree.
the holesbut canholes.They lie buried in the muck in the bottom of
makeslimygalleriesandinglassbottlesextendthesegalleriesalong
In fact, they
the sides of the bottle up to the surface of the rvater.
together rvibh themake a tube of the debris, cementingthe particles
caseof a oaddissame slimy suhstance,*"Li"g a home very like thethis insect is lhe
fly. The most interesting singie feature in the life ofabove that
descrihedsecretion
following : Apparently it i* ihu ,"*.
of captupurpose
theforis usedboth as a bait for insectlarvae andas foodthemtoring them. 'Ihe Stegomyialawae that were given
the strbstance'in the laboratory uie rremendously eager to feed onan abunjar
containing
afrom
justtahenbeen
Dven though they haveonce
momentt
theathungrytlance of food and are apparently not

THE

GENUS SIG} T AT OM ERA OS TE N S A C K E N

7they come in contact with the substancethey cannot leave ib aloneand lose all senseof discretionin the face of the peril that confronts
them. While they are feeding, the Sigmatomeralarvaelie quietly andevery now anclthen touch one of the stegomyialarvae with the substance and immediately it is bound a helplessprisoner.Usuallv theIarva is attached to the debris, bub occasionallythe head is glued
to the caudal end, forming a curled sausage-shapedstructure. whilein this condition and being devoured hy the sigmatomera,the otherstegomgialarvae feed on the substanceand continue to do this into
the very jaws of the Tipulid larva. > 1\{r. Shannon further remarksthat the larval stage is of long duration and probably can be prolonged indefinitely in natnre in the absenceof sufficientfoocl,but thepupal stageis shorl.
I\{r. Shannon's interesting notes may pe compared rvith the brief
observationsavailable concerningthe larval habitat of Astelobiaru!a
Hudson, as recordedby Hudson (1920).The larva lives in and feeds
on the semi-liquid vegetable detritus rvhich accumulates in large
quantities at the basesof the leavesol Astelia solandri, a commonand very conspicuousepiphytic plant in most of the primaevar nativeforests around Wellington, Nerv Zealand. Apparently only a single
larva inhabits the space betrveenthe tu,o sheathingleaves.of theAstelia, and only those leavesrvhich are full of a thick, brou,n, co{Teelike liquid are frequented. The pupa is enclosedin a rather tough,extremely elongatesilken tube situated betn'eenthe sheathinglear.es.
It rests in an upright position in the midst of the semi-riquidmass.
From the relationships with Sigrnatomera,and the fact that only asingle larva is found in a compartment, it may reasonablybe s'spected that the lan'ae of Astelobiq are likwise entirely predaciouson
smaller organismsliving in the environment.

I,ITERATURE.
A lnxlivo nn (C. P.) :L944a. Transactions Amorican llnt. Soc., 40 : 246, pl 3, fig. I(,5. apicalis).
19 14 b. En tom ol. Nor v s ,25 : 209- 2, t 0,pl . 9, fi g . b ( S . occultal.
19 20 . Ca na dian Ent om ol. , 52 : L42- t 4B ( allo t y p e o f ,5. amazonica).
19 2'J. Pro c. L inn. Soc . Nen' Sout h W ales , 52 : S S .

Huns ox ( G . V . ) :1920.T r ans a c ti o nNs c rvZ e a l a n dIn s t.,5 2 :32-33, pl . { , fi g.7-9 (i mmature stagesAstelobiarufa).
"

CIIARL ES

P. AI,EXA N D E R

O s r s N- S ec r n r,r(C . R .) :1869.MonographsDiptera North America, 4 : 1 3 7 - 1 3 8 ( d e f i n i t i o n o f
Sigmatomera).
1,8 73 .Ibid. , 3 : addenda, p. lx ( ^S.f lar : i p e n n i s l .
18 87 . B er liner Ent or nol. Zeit s c lir . , ll: 20 5 .
Rrr:nn r, (M. P. ) :1921. Archiv fiir Naturgcschichtc, 87, Atrl. A : 124-121>, fig. a-c(5. occulta, as flavipennis).
\\'as'rrvo oo (i.O . ) :1 88 1. Tr ans ac t ions Eut om ol. Soc . Lond o n . 1 8 R 1 : S 6 6 - 3 6 7 ,p l . 1 7 , f i g . 3(,9. amazoniaa\.

Dip te r a , t. Y, fa sc. 4 , r 5. l l , rq3o.
( Pa r is. P. L e ch e r al i er).