DESCRIPTION OF IMMATURE STAGES OF PLATYVELIA BRACHIALIS (STAL) (HETEROPTERA : VELIIDAE)

7 Pages·1999·3.2 MB·

by  P P Korch

PROC. ENTOMOL. SOC. WASH.
101(2), 1999, pp. 372-378
DESCRIPTION OF IMMATURE STAGES OF PLATYVELIA BRACHIALIS
(STAL) (HETEROPTERA: VELIIDAE)
Peter P. Korch, Steven L. Keffer, and Elisa Winter
(PPK) 1911 Bigler Avenue, RO. Box 367, Spangler, PA 15775, U.S.A.; (SLK, EW)
Department of Biology, James Madison University, Harrisonburg, VA 22807, U.S.A.
(SLK e-mail: [email protected])
—
Abstract. The five immature instars of the broad-shouldered waterstrider, Platyvelia
brachialis, are described for the first time. Of three characters considered diagnostic for
adult Platyvelia only one, patches ofsilvery setae on the abdominal dorsum, was observed
on immatures of P. brachialis.
Key Words: Broad-shouldered waterstriders, Platyvelia brachialis, Veliidae, Heteroptera,
immature insects
During a collecting trip to northeastern The veliids would then walk out onto the
North Carolina in August 1994, the two se- water, away from the banks, at which time
nior authors collected a complete series of they were easily collected from the water
immature instars for the veliid species Pla- surface with an aspirator In addition to the
tyvelia brachialis (Stal). We here provide immatures described below, 27 adult males
the first description ofthe five immature in- and 24 adult females were collected. All the
stars of this species. Readers wishing to adults were inacropterous.
learn more about the adults of Platyvelia Descriptions were based on 3 first, 4 sec-
brachialis should consult Polhemus and ond, 5 third, 6 fourth, and 4 fifth instar
Polhemus (1993) and the references therein. specimens. Dorsal habitus illustrations were
Excellent, more general treatments of ve- produced using a camera lucida mounted on
liids can be found in Andersen (1982), a Zeiss Stemi SV6 stereomicroscope.
Smith (1988), and Schuh and Slater (1995). Voucher specimens have been deposited
in the first author's private collection.
Materials and Methods
Descriptions
Specimens were collected along the
—
mm
banks ofstagnant bodies ofwater at the fol- First instar (Fig. 1). Length, 1.25
lowing localities in northeastern North Car- ± 0.09 mm; width, 0.61 mm ± 0.03 mm.
olina: Washington Co., Thirty Foot Canal, Body elongate and elliptical, greatest width
near junction of Thirty Foot Canal Rd. and at mesothorax; general ground color ochre-
Tom Pepper Rd., 12, 13 August 1994; ous; covered with dense, short setae.
Washington Co., ca. 1 km. E. of Creshell Head declivent, dorsally brown, ventrally
near junction of Old Cherry Rd. and ochreous, vertex with dark median stripe;
Springhill Rd., 12 August 1994; Tyrell Co., anteclypeus protruding, rounded anteriorly;
Batavia Canal, ca. 2 km N. or Lake Phelps, remainder of head excluding eyes subrec-
13 August 1994. They were collected by tangular; ecdysial lines ochreous, Y-shaped,
disturbing the vegetation along the banks. stem wider than arms, arising from poste-
VOLUME NUMBER
101, 2
373
Figs. 1-2. Platyvelia brachialis. 1. First instar. 2, Second instar. Scale bar = mm.
1
374 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
nor margin of head, arms extending to an- chanter without ventral spines, ca. Vi length
teroinferior margin of eyes. Eyes globose, of tarsus; femur slightly curved, ochreous
red, separated by ca. 1.6X width of eyes; at distal tip, double row of spines absent,
ocular setae absent. 3 pairs of trichobothria subequal to slightly longer than tibia; tibia
present, 1st pair just posterior to antecly- straight, ventral spines absent, anterodistal
peus, 2nd pair posterolateral to 1st pair, 3rd hair tuft present but less dense than on pro-
pair just medial to inner margin of eyes. tibia, grooming comb present; tarsus
Antenna 4-segmented, brown with seg- straight, ca. % length of tibia, subapical
ments 1 and 2 darker than 3 and 4; segment claw slender, longer than protarsal claw.
1 curved, segment 2 shortest, segment 4 Metathoracic coxa elongate, subrectangular,
longest and tapered apically. Beak 4-seg- constricted proximally but not rounded dis-
mented, segments 1-3 ochreous, 4 brown; tally, shorter than trochanter; trochanter
segment 2 shortest, segment 3 longest, seg- without ventral spines, subequal in length
ments 1 and 4 subequal. to tarsus; femur slightly curved, ochreous
Thoracic nota each with pair of sclero- at distal tip, subequal to slightly longerthan
tized, brown subrectangular plates covering tibia, single row of 4-6 short, thick spines
most of dorsum, each wider laterally, sep- ventral; tibia straight, single row of 13-15
arated medially by an ochreous ecdysial thin recurved spines on ventral surface, an-
membrane which widens posteriorly; pro- terodistal hair tuft absent, grooming comb
notal plates extending further laterally than present, tarsus straight, ca. Vi length oftibia,
meso- and metanota, mesonota extend only subapical claw similar to mesotarsal claw.
slightly further laterally than metanota. Abdomen ochreous. Tergum 1 with pair
Dark fovea present on each pronotal plate of rectangular mediotergites widely sepa-
roughly in line with anteromedial corner of rated by medial ecdysial membrane, later-
eye; shallow oblique depression lateral to otergites absent. Terga 2—8 with pair of
fovea extending anterolaterally. Meso- and rectangular mediotergites, lateral margins
metanota with dark longitudinal markings slightly lateral to medial margins of 1st me-
in line with posteromedial corner of eyes. diotergites, narrowly separated by medial
Thoracic pleura and sterna ochreous, mem- ecdysial membrane; two pairs of lateroter-
branous; supracoxal lobes sclerotized and gites present, the first small, narrowly and
pigmented brown. irregularly elliptical, found on anterior mar-
Legs brownish dorsally, ochreous ven- gin of segments, the second minute, located
trally, setose throughout; mesothoracic leg intrasegmentally, distal to first, both absent
longest. Prothoracic leg somewhat raptorial; on segment 8; distance between medio- and
coxa globose distally, subequal in length to laterotergites decreases posteriorly. Spira-
trochanter; trochanter ventral margin longer cles present dorsally on segment 1, laterally
than dorsal, subequal in length to tarsus, 5- on segments 2—7. Minute pleurites present
7 spines on ventral surface distally; femur on segments 2-7. Venter mostly membra-
slightly curved, ochreous at distal tip, ca. 1 nous, pair of sclerites present medially on
VsX longer than tibia, proximal Va of ventral segment 8. Segment 9 cone-shaped, scler-
margin with double row of spines; tibia otized dorsally and laterally. Segment 10
slightly curved, row of short, thick spines only visible ventrally, enclosed dorsally and
anteroventrally, longer, thinner spines pos- laterally by segment 9. —
teroventrally, tuft of hairs anterodistally, Second instar (Fig. 2). Length, 1.70
grooming comb distally and posteroventral; mm ± 0.05 mm; width, 0.74 mm ± 0.04
tarsi straight, 1-segmented, subequal in mm.
length to trochanter, short, paired claws Ground color slightly darker than first.
subapical. Mesothoracic coxa globose dis- Antennal tubercles more distinct.
tally, subequal in length to trochanter; tro- Pair of dark foveae present on each pro-
VOLUME 101, NUMBER 2 375
notal plate, medial fovea in line with an- tarsi ochreous. Prothoracic trochanter with
teromedial margin ofeye, lateral fovea pre- 8-12 spines on distoventral surface; femur
sent in medial end ofoblique depression, in ca. 1.6X longer than tibia, spines extend
line with lateral margin ofbase ofantennae, nearly length of ventral surface. Mesotho-
area between foveae of each plate slightly racic tarsus ca. 0.7X length of tibia. Meta-
depressed. Meso- and metanotal plates with thoracic femur with double row of 9-11
dark, narrowly U-shaped longitudinal short, thin spines; femur slightly longer
markings in middle, open anteriorly. than tibia.
Ventral surface oflegs brownish. Protho- Stemite on abdominal segment 8 heavily
racic femur ca. 1.4X length of tibia; faint setose.
yellow band in distal V3. Tibia with faint Otherwise similar to —second instar.
mm
ochreous band in middle third. Mesothorac- Fourth instar (Fig. 4). Length, 3.04
ic trochanter with pair of denticles on dis- ±0.18 mm; width 1.13 mm ± 0.10 mm.
toventral aspect. Femur with faint yellow Body more elongate, greatest width at
band in distal third. Tibia with faint ochre- metathorax. Ground color darker. Eyes sep-
ous band in middle third; double row of arated by ca. 1.6X width of eyes. First an-
spines present, shorter and fewer than that tennal segment ca. 1.4X length of fourth
ofprofemur. Tarsus ca. 0.8X length oftibia. segment; darker in proximal Vs. Second an-
Metathoracic trochanter with 3-4 short tennal segment with faint yellow band in
spines on distoventral aspect. Femur with proximal V2.
double row of 7-9 ventral spines, dorsal Mesothoracic wing pad nearly extends to
row longer, more robust; faint yellow band posterior border of metanotum; metathorac-
in distal half. Tibia with faint ochreous ic wing pad nearly extends to posterior bor-
band in middle V4. der of first abdominal segment.
Abdominal mediotergites of segment 1 Mesothoracic tarsus ca. 0.6X length of
lightly pigmented, subrectangular, narrowly tibia. Metathoracic tarsus ca. 0.4X length of
separated by ecdysal line; mediotergites of tibia.
segments 2-8 greatly reduced, taking on an Thin patch of silvery pubescence present
irregular elliptical shape, located anteriorly on distolateral margins of abdominal seg-
along intersegmental fold; all mediotergites ments 2-7; ecdysal line forming ovate
forming a parallel row in line with the me- patch at anterior margin of segment 7, a
dial prothoracic foveae. Laterotergites pres- smaller pair of ochreous spots lateral to ec-
ent on segment 1 as small elliptical disks dysal patch between the medio- and lateral
along intersegmental membrane with meta- tergites. Medial V2 ofdorsal surface segment
thorax. Segment 9 with ecdysial line. 8 ochreous; sexual differentiation apparent
Otherwise similar to—first instar. on ventral stemite of segment 8
mm
Third instar (Fig. 3). Length, 2.10 Otherwise similar to—third instar.
±0.16 mm; width, 0.95 mm ± 0.04 mm. Fifth instar (Fig. 5). Length, 4.16 mm
Ground color darker. Eyes separated by ± 0.23 mm; width, 1.48 mm, ± 0.10 mm.
ca. 1.2X width of eye. Antennal segment 1 Ground color darker, patterns more dis-
subequal to segment 4. tinct. Antennal tubercles more distinct,
Posterior margin of pronotum extends nearly black; anteclypeus, postclypeus, and
posterior at midline. Lateral foveae in line posterior margin ofhead nearly black. Eyes
with posteromedial margin of eyes. Meso- separated by 1.4X width of eyes. First an-
notal wing pads present, extending poste- tennal segment ca. 1.6X length of segment
riorly ca. Vi length ofmetanotum. Metanotal 4; segments 2 and 3 subequal.
wing pads extend ca. V2 length of first ab- Pronotum with dark brown markings ex-
dominal segment. tending anterolaterally from lateral foveae
Leg bands more distinct; proximal V2 of to anterior margin of pronotum and poste-
,
376 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
Figs. 3-4. Platyvelia hrachialis. 3, Third instar. 4, Fourth instar. Scale bar = 1 mm.
riorly V^ the length of the lateral margin. riorly ca. Ya length ofabdominal segment 1
Posterior V3 raised, quadrate and widened nearly covering metanotal pad. Distal tip of
laterally. Midline elevated, reaching highest metanotal pad curved laterally, extending
point at posterior margin. just distal to mesonotal pad.
Wing pad darker, more developed. Me- Prothoracic femur ca. 1.2X length oftib-
sonotal pad with a broad, setose, semilunar ia. Tibia ca. 2.5X length of tarsi, yellow
elevation in medial %; pads extend poste- band on posterior of proximal V4; anterior
VOLUME 101, NUMBER 2 377
Fig. Plalwelia bracliialis. fitth instar. Scale bar = 1 mm.
surface yellow. Mesothoracic tibia with yel- morphy, silvery setae on the abdominal
low band on posterior of proximal Va; an- dorsal surface (and on the hemelytra of
terior surface yellow. Metathoracic tibia ca. winged adults), begins in the 4th instar, but
4.3X length of metatarsus; yellow band in only as small intersegmental areas between
proximal V4. segments 2-7. Larger areas of silvery setae
Pubescence present along distolateral appear on the dorsal abdominal surface of
margins of abdominal segments 2-7 more instar 5, but these are not present in a dis-
distinct; additional pubescence present in tinct pattern. The final apomorphy is the
random patterns along dorsal surface of lack ofocular setae, a trait shared with Stei-
segments 3-7. Segment 7 with dark yellow novelia. We found no evidence of ocular
ovate spot present along anterior portion of setae in any instar. Thus, ofthree characters
ecdysal line. Segment 8 with anterior mar- considered diagnostic for adult Platyvelia
gin dark yellow, expanding along ecdysal only one, patches of silvery setae on the
line posteriorly; ventral aspect completely abdominal dorsum, was observed on im-
covered by sternites. Segment 9 usually matures of P. brachialis.
with most of dorsal surface yellow.
Acknowledgments
Otherwise similar to fourth instar.
We thank John T Polhemus and an anon-
Discussion
ymous reviewer for their critical review of
Polhemus and Polhemus (1993) list three the manuscript.
apomorphies for the genus Platyvelia. The
first, opposing metastemal and mesoaceta- Literature Cited
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specimens of P. brachialis. This is there- miptera. Gerromorpha): Phylogeny, Adaptations,
fore an adult character. The second apo- Biogeography, andClassification. Entomonograph
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
378
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