Curictan copulation and waterscorpion higher classification (Heteroptera: Nepidae)

5 Pages·1993·2.1 MB·

by  S L Keffer

PROC. ENTOMOL. SOC. WASH.
95(1), 1993, pp. 74-78
CURICTAN COPULATION AND WATERSCORPION HIGHER
CLASSIFICATION (HETEROPTERA: NEPIDAE)
S. L. Keffer and J. E. McPherson
(SLK) Department ofEntomology, National Museum ofNatural History, Washington,
D.C. 20560; (JEM) Department ofZoology, Southern Illinois University at Carbondale,
Carbondale, Illinois 62901.
Abstract.—The copulatory posture ofCuricta howardi is described in detail. One aspect
ofcurictancopulation, thegraspingofthefemale'sheadbythemaleprotibia, istentatively
identified as unique to thegenus and therefore diagnostic. We relate ourobservations and
those ofpreviously studied waterscorpions to the currently accepted higher classification
ofthe Nepidae (Lansbury 1974) and conclude that copulatory posture may be ofsubfa-
milial significance, thereby lending support to the inclusion of Curicta in the subfamily
Nepinae. However, copulation has not been studied in two key genera, the Australian
endemics Austronepa and Goondnomdanepa. Both of these genera are currently placed
in the subfamily Ranatrinae but also possess certain ofthe tribal characteristics oi^Curicta
and the other Nepinae genera. Thus, ifthey are found to copulate in a nepine/curictine
manner,thencopulatorypostureasasupragenericcharacterwouldcontributetothetribal,
rather than the subfamilial, classification ofthe family.
Key Words: Curicta howardi Montandon, waterscorpion copulation, Nepidae higher
classification, Heteroptera
Little is known about copulatory behav- ofAltairatRoute90,ColoradoCounty.The
iorinwaterscorpions. Thusfar, information second population was collected from San
is available only for Curicta howardi Mon- Fernando Creek at Route 44, 1 km east of
tandon (Wiley 1922, 1924), Laccotrephes Alice, Jim Wells County. The specimens
fabricii St^l (Mattel 1965), Nepa cinerea L. were maintained in 5 gallon aquaria with a
(Poisson 1924, Larsen 1938), and Ranatra sloping sand beach at one end and approx-
linearis L. (Larsen 1938). This paper pre- imately 1 inch of deionized water at the
sents further information on copulation in other end. The aquaria were kept in incu-
Curicta howardi and relates our observa- bators under identical rearing conditions
tions to the currently accepted higher clas- approximating the May-July photoperiod
sification ofthe Nepidae (Lansbury 1974). and temperatures in the collection area, i.e.
14L:10D photoperiod and 27.5-28.9°C.
Methods and Materials
Smallpiecesofplasticaquariumplantswere
In July of 1988, two populations of C. placed in the water to provide a perch for
howardi were collected from the Coastal the adults. Aquaria were cleaned weekly or
Plain region of Texas and returned to the more often if they became fouled. Speci-
laboratory at Southern Illinois University mens were fed a variety offoods, primarily
atCarbondale, Illinois. The first population Corixidae and small Bueno sp. (Notonec-
was taken from Skull Creek, ca. 2 km west tidae), approximately 1.5 food items/day.
VOLUME NUMBER
95, 1 75
Fig. 1. Maleand female C. howardiin copula, dorsolateral view(barscale 3 mm). M = male; F= female;
OP = male operculum.
The aquaria were checked irregularly the adjacent paraclypeus. His mesofemur
throughout both the incubator's day and was thrown over the dorsum of her abdo-
nightcycleforcopulatingpairswhich, when men posteriorto the scutellum, and his me-
discovered, were preserved for study by sotibia was flexed ventrally under her ab-
spraying with ethyl chloride followed by domen. His metathoracic leg extended
freezer storage. Photographs were taken on posteroobliquely over her abdominal dor-
mm
Kodak Panatomic-X film with a 35 sum; his metatibia was not flexed under-
ContaxcameraadaptedtoaZeissSRStereo neath. In preparation for copulation, the
microscope. male twisted the distal halfofhis abdomen
ventrally under the female. This manuever
Results
considerablydeformed the male'sabdomen
Copulation was observed in the labora- and placed his last abdominal tergum
tory on a daily basis but only during the obliquely underneath the female's genital
night cycle of the incubator. Duration of operculum (Fig. 2). The two plates of the
copulationevents varied from about 5 min- male's last abdominal tergum separated
utes to 8 hours. (It is possible that the short medially and he extended the genital cap-
copulationswerenotcompletedeventhough sule anterodorsally, effectively placing the
the male had assumed the copulatory pos- capsule upside down relative to its usual
ture outlined below.) Lengthy copulations orientation in his body and pointing ante-
were not unexpected because two of the riorly; atrest thecapsuleand enclosed phal-
adults used in this study were collected in lus point posteriorly. Duringcopulation the
copula in the field and remained thus for male's parameres hooked onto the female's
abouteight more hours. Noapparent court- first gonapophyses.
ship behavior was detected prior to copu-
Discussion
lation.
At the onset ofcopulation, a male would Wiley (1922) observed C. howardi spec-
approach a female, usually from her right imenscopulatingshortlyaftertheyhadbeen
side, and grasp her with his three adjacent taken from the field and placed in a com-
legs (Fig. 1). In this grasp, his protibia was mon container. She noted that "the male
hooked over her head between the eye and takes a position to one side of the female,
76 PROCEEDINGSOFTHE ENTOMOLOGICALSOCIETY OFWASHINGTON
Fig. 2. Male and female C. howardi in copula, terminal abdominal segments, ventral view (bar scale = 2
mm). M = male; F = female; OP = male operculum.
and usually to the right. Ifto the right, he cinerea (Poisson, 1924: plate 5, fig. 15; Lar-
hooks his left anteriortarsus over her head; sen, 1938: 58, fig. 19), the male lies to one
ifto the left, the right fore tarsus is used" side and partially above the female as in
(p. 507). She observedthat matingoccurred Curicta but does not hook his protibia over
almost daily from early spring through late the female's head. The protibia of the L.
summer (Wiley, 1924: 327) and that the fabricii male grasps the female by the an-
duration ofcopulation often lasted several terior half of the pronotum while the me-
hours. Our results confirm Wiley's obser- sothoracic leg clasps her at the junction of
vations regarding both the male preference her pronotum and abdomen. The protibia
for grasping the female from her right and ofthe A^. cinerea male grasps the female by
the often long duration ofthe copulations. theposteriorpartofthepronotumwhilethe
In one respect, however, our results differ. mesothoracicleggraspsthedistalhalfofher
In our laboratory cultures males always abdomen. The metathoracic leg ofboth L.
hookedtheirprotibia,notjusttheprotarsus, fabricii and A'", cinerea extends postero-
overthefemale'shead. Interestingly,theuse obliquely over the female abdominal dor-
ofthe protibia/tarsus to grasp the female's sum as occurs in C howardi. Mattel (1965)
headduringcopulationappearstobeunique neither illustrated nor described the place-
tothegenus(see below). Thus, thistraitcan ment of the male abdomen of L. fabricii
tentatively be considered diagnostic for underneath the female other than to say on
Curicta. page 78, "le male glisse son extremite ab-
Copulatory posture in two of the three dominaleau-dessousdeI'abdomen dela fe-
other waterscorpion species studied resem- melle." However, his dorsal illustration of
bles that observed for Curicta howardi. In a copulating pair (p. 75, fig. 8C) shows the
L.fabricii(Mattel, 1965: 75, fig. 8C) and TV. male respiratory siphons at about a 45° an-
VOLUME 95, NUMBER 1 77
gletothefemale'ssiphons. Thissiphoncon- ni. Ten morphological characters are used
figuration is similar to that illustrated and in the Lansbury classification: four are
discussed for A^. cinerea by Larsen (1938) weighted as subfamilial and six as tribal.
suggesting that the same abdominal defor- Curicta is assigned to the subfamily Nepi-
mation occurs in L. fahricii. During copu- nae because ithasthe same foursubfamilial
lation in R. linearis, the male does not de- charactersasthegeneraoftheNepini. How-
formtheabdomen(seebelow)andthemale's ever, atthe tribal level, Curictaiscongruent
siphons diverge from the female's siphons with the Nepini for only 2 characters and
at approximately 15°. As in C. howardi, the with the Ranatrini fortheremaining4char-
male A'^. cinerea deforms his abdomen to acters. Similarly, Austronepa and Goond-
place the dorsum ofhis last abdominal seg- nomdanepa are assigned to the subfamily
ment underthe female's operculum (Larsen Ranatrinae because they possess the same
1938: p. 60, figs. 20-22) and the phallus is subfamilial characters as the genera ofthe
inserted upside down and backwards rela- Ranatrini but at the tribal level, Austronepa
tive to its resting position. and Goondnomdanepa are congruent with
The male ofR. linearis assumes a some- only four of six and one of six Ranatrini
what different copulaton^ posture (Larsen characters, respectively, whileagreeingwith
1938: p. 80, fig. 37). Instead of lying im- the Nepini on the remaining characters.
mediately adjacent to and partially on top Hence, thesethreegeneraareeach accorded
ofthe female as occurs with Curicta, Lac- theirown tribeandareunderstoodas "tran-
cotrephes, and Nepa, the male Ranatra an- sitional" because they each possess a mix
gles the anteriorpart ofhis body away from ofNepini and Ranatrini character states.
the female while still hooking his profemur Laccotrephes and Nepa belong to the
and tibia midway over her pronotum and Nepinae-NepiniandRanatrabelongstothe
his mesofemur and tibia over herabdomen Ranatrinae-Ranatrini. The deformation of
justanteriortotheinnerangleofthe hemel- the male abdomen duringcopulation found
ytral membranes. By anglingaway from the in Curicta, Laccotrephes, and Nepa further
female, the male is able to place his last aligns Curicta with the Nepinae. Unfortu-
abdominal segment under her operculum nately, nothingiscurrentlyknownaboutthe
withoutdeforminghisabdomenasin Curic- copulatory postures of the other two tran-
ta, Laccotrephes, and Nepa. During copu- sitional waterscorpion genera, Austronepa
lation, Ranatra linearis inserts an upside- and Goondnomdanepa. The Nepinae, in-
down, backward phallus (p. 82, figs. 38-39) cluding Curicta, all have visible abdominal
as do Curicta, Nepa, and presumably Lac- parasterna, whereas the Ranatrinae, includ-
cotrephes. ing the transitional Australian genera, have
The Nepidae are currently divided by the parasterna infolded (Menke and Stange
Lansbury(1974)intotwosubfamilies(Nep- 1964, Lansbury 1974). Could it be that this
inae. Ranatrinae) and five tribes (Nepini, parasternal infolding structurally prevents
Curictini, Goondnomdanepini, Austrone- the male Ranatrinae abdomen from twist-
pini, Ranatrini). According to this higher ingunderthefemale'sabdomenduringcop-
classification, Curicta (Curictini) is one of ulation? If it is found that males ofall the
three "transitional" (pp. 222-223) genera. Ranatrinae genera do not deform their ab-
along with two Australian endemics, Aus- domens during copulation, then this aspect
tronepa (Austronepini) and Goondnomda- of waterscorpion copulatory posture will
nepa (Goondnomdanepini), between the constitute an additional character in sup-
genera ofthe tribe Nepini with their broad, port of Lansbury's subfamilial classifica-
dorsoventrally flattened bodiesandthenar- tion. If, however, males ofAustronepa and/
row, tubular-shaped genera ofthe Ranatri- or Goondnomdanepa are observed to twist
78 PROCEEDINGSOFTHE ENTOMOLOGICALSOCIETY OFWASHINGTON
theirabdomensunderthe femaleintheNe- (Hemiptera-Heteroptera). Journal ofthe Austra-
pini/Curictinimanner,thencopulatorypos- lian Entomological Society 13: 219-227.
Larsen, O. 1938. Untersuchungen iiber den gesch-
ture will constitute a tribal character in the
lechtsapparatderaquatilenwanzen.OpusculaEn-
Lansbur> classificationthusfurthercontrib- tomologica (Suppl.) 1: 1-388.
utingtothe mixingofNepini and Ranatrini Mattei, C. 1965. Morphologic et biologic de Lacco-
characters in the three transitional genera. trephes fabricii StSl, 1868 (Insecte Heteroptere,
Hydrocorise, Nepidae). Annalesdela Facultedes
Acknowledgments Sciences, Universitede Dakar 18: 59-94.
We are indebted to Dr. Peter P. Korch of Menkoef,NeAp.iSd.aeanfdroSmtaAnugset,raLl.iaAw.ith19n6o4t.esAonntehewhgiegnhuesr
Bamesboro, PAforhelpcollectingthe spec- classificationofthefamily.ProceedingsoftheRoyal
imens ofC. howardi. We also would like to Society ofQueensland 75: 67-72.
thankDr. DavidG. KingoftheDepartment Poisson,R. 1924. ContributionaI'etudedesHemip-
of Anatomy and Steve Taylor of the De- t^resaquatiques. Bulletin BiologiquedelaFrance
et de la Belgique 58: 51-305.
partmentofZoology, Southern IllinoisUni- Wiley, G. O. 1922. Some notes on the biology of
versity, fortakingthephotomicrographsand Curicta from Texas. Kansas University Science
suggesting the use ofethyl chloride respec- Bulletin 14(20): 507-511.
tively. . 1924. OnthebiologyofCurictadrakeiHun-
gerford (Heteroptera, Nepidae). Entomological
Literature Cited News 35: 324-331.
Lansbury, I. 1974. A new genus of Nepidae from
Australiawitharevisedclassificationofthefamily