Chorionic fine structure of the egg of the Oak tingid, Corythucha arcuata (say) (Hemiptera: Tingidae)

4 Pages·1994·1.2 MB·

by  G T Baker

PROC. ENTOMOL. SOC. WASH.
96(1). 1994, pp. 70-73
CHORIONIC FINE STRUCTURE OF THE EGG OF THE OAK TINGID,
CORYTHUCHA ARCVATA (SAY) (HEMIPTERA: TINGIDAE)
Gerald T. Baicer and Richard L. Brown
Department ofEntomology, Mississippi State University, Box 9775, Mississippi State,
Mississippi 39762.
Abstract.—TheeggofCorythuchaarcuataconsistsoftwodistinct regions, 1)thesmooth
basal portion that is sun-ounded by an unknown substance secreted by the female and 2)
the operculum that is made up ofan apical rim and cap and the most distinctive area of
the egg. Reticulations cover the outer and inner surfaces ofthe rim, that projects outward
and varies in height. The lower portion ofthe cap that fits into the rim is smooth and
then the cap bulges outward dorsally and has a reticulated surface. The upper portion of
thecap consists ofover-lappingpieces ofchorion. Both the rim and cap are highly porous.
The thick exochorion is separated from the thin endochorion by irregularly spaced tra-
beculae. A vitelline membrane with a fibrous appearance is situated just beneath the
chorion.
Key ll'ords: Hemiptera, Tingidae, Corythucha, egg, chorion, operculum
Information on thestructureofinsecteggs ythucha species. In this paper we describe
hasbeen usedtoindicatephylogenetictrends the chorionic fine structure and opercular
in families within Hemiptera (Southwood region ofC. arcuata eggs.
1956, Cobben 1968). Hinton (1981) also
Materials and Methods
presentsdataonthestructureofhemipteran
C
eggs including a cursory description oftin- Eggs of arcuata were taken from the
gid eggs. Livingstone and Yacoob (1987) underside of oak leaves. Fifteen eggs were
and references therein provide the only de- fixed overnight in 4%glutaraldehyde in Na-
tailed biosystematic reviews of Tingidae cacodylatebuffer(pH 7.2)at 4°C. Afterrins-
based on morphological and biological de- ing in buffer, some specimens were soni-
tails of the egg stage. Lace bugs belonging cated to remove a covering placed over the
to the genus Corythucha feed on a wide \a- eggs by the female lace bug. The sonicated
riety of deciduous shrubs and trees, and and non-sonicated eggs were post-fixed in
populationsofthesespeciesoften reach pest 2%OsOjfor4handthenwashedindistilled
status. The oak lace bug. Corythucha ar- water. Prior to critical point drying, the
cuata (Say), has been recorded from apple, specimens were dehydrated in a graded se-
maple, and roses, but feeds primarily on ries ofethanol. The eggs were mounted on
species ofQucrcus. Morrill (1903) and Bai- stubs with double-sided sticky tape, coated
ley (1951) provided descriptions ofthe egg, with gold-palladium, and examined with a
nymph, and adult stages ofC. arcuata and Cambridge 360 scanning electron micro-
other Corythucha. Thereare nodetailed ac- scope at 15 kV. Images were recorded on
countsofthechorionicstructureofanyCor- Polaroid Type 55 film. Eight eggs were pro-
VOLUME NUMBER
96. 1 71
cessed for mounting in balsam and mea- thick and has a matted, fibrous appearance
surements of these eggs were taken with a (Fig. 8).
light microscope with a calibrated ocular
micrometer. Discussion
Within the family Tingidae there are sev-
Results
eral ways in which eggs are oviposited on
Eggs are situated on the underside ofoak leaftissue, and theseareput forth by South-
leaves in loose clusters. The tapered pos- wood(1956)andCobben (1968). According
terior end of the egg is deposited into the to Cobben (1968) the deposition ofeggs in
leaftissue on the lower surface in a vertical batches and vertical position is considered
position. The exposed apical end is covered as being(1) primitive, (2) parsimonious use
by an unknown substance produced by the ofspace, and (3) associated with some form
female (Fig. 1). The exudate has a rough ofparental care. Also species within genera
appearance and is unevenly coated overthe of Tingidae exhibit a wide variety of ovi-
exposedoutersurfaceoftheegg(Fig. 1). The positional behaviours such as those pre-
length ofan egg is 583 ixm (563-604 Mm. N sented by Livingstone and Yacoob (1987)
= 8)and 206 ^m (199-21 mhi, N = 8)wide. and Bailey (1951) which provide oviposi-
Thereisnoornamentation ontheoutercho- tional details on the various species ofCor-
rionic surface (Fig. 2). The chorion consists ythucha. Eggs of C. arciiata can be differ-
ofanexochorion that is2.8 i^rn (2.7-3.0^m) entiated from otherspecies oiCorythiica by
wide and an endochorion 0.19 ^m (0.17- the shape and size of the cap and rim,
0.21 nm) wide (Fig. 3). Irregularly spaced whether or not the egg is coated after ovi-
trabaculae separate the two portions ofthe position, the type ofhost plant, and where
chorion (Fig. 3). and howtheeggisplacedin the plant tissue.
The apical or opercular area ofthe egg is These criteria were used by Morrill (1903)
the most distinctive, consistingofa rim and toseparatethreespeciesofCorythucha. The
acapwithalongfilamentousextension(Fig. external coating that is placed on the eggs
4). The rim, which encircles the apex ofthe ofC. arcuataoccurs in otherspeciesofCor-
egg, varies in height from 8 ^m to 27 /^m ythucha and in other genera as well (Dick-
and is covered by reticulations on both sur- erson and Weiss 1916, Johnson 1936, Bai-
faces (Figs. 4, 5). The rim projects outward ley 1951, Livingstone and Yacoob 1987,
in order to accommodate the cap so that it Neal and Douglass 1988). This coating
is secured on the apex ofthe egg by the rim which is produced by the female probably
(Figs. 4, 5). prevents the desiccation ofthe eggs which
Arelativelysmoothbandofchorionforms are exposed to air currents that pass over
the lower portion ofthe cap (Fig. 4) and the the leaf surface. Livingstone and Yacoob
cap bulges outwardjust above this smooth (1986) and Neal et al. (1991) showed that
area (Fig. 4). The surface ofthe protruding the coating on tingid eggs did not deter at-
portion and the lower division of the cap tacksofparasitoidsorpredatorson theeggs.
are deeply reticulated (Figs. 5, 6), whereas The cap and rim are the only portions of
the upper division of the cap is faintly re- the eggs that exhibit any type of variation
ticulated, rough-textured, and has a layered from genus to genus and species within a
appearance (Fig. 5). Except for the smooth particular genus. In earlier descriptions of
bandat thebottom, thecapishighly porous C. arcuata eggs, such as Morrill (1903) and
(Figs. 5, 6) and the inner surface is smooth Bailey(1951), reference is made to the ridg-
(Fig. 7). Immediately beneath the chorion es that occuron the cap but ridges were not
is the vitelline membrane which is 0.03 ^m observed on the cap of the specimens ex-
72 PROCEEDINGS OFTHE ENTOMOLOGICALSOCIETY OFWASHINGTON
Figs.1-6. Corythuchaarcuataegg. Fig. 1. Looseclusterofeggsonthelowerleafsurfaceinaverticalposition
withoutercovering.Fig. 2. Rim,cap.andfilamentoftheoperculum. Fig. 3.Sectionthroughthechorionshowing
the e.xochorion and endochorion separated by trabeculae. Fig. 4. Cap and rim separated. Fig. 5. Cap and nm
joined; cap with reticulate surface. Fig. 6. Layers ofthe cap (arrows)and porousareas within the reticulations.
C = cap, EN = endochonon, EX = e.xochorion. F = filament, R = rim, T = trabeculae.
VOLUME 96. NUMBER 1 73
Figs. 7, 8. C. arcuata egg. Fig 7. Smooth band at the bottom ofthe cap and no sculpturing on the inner
surface. Fig. 8. Reticulate mner suiface ofthe rim and the vitelHnecovering.
amined for this paper. There is no mention Leptoypha inutica Say. Entomological News 27:
ofthereticulatedsurfaceoftherimandlow- 308-310.
er portion ofthe cap or the layering on the Hinton,H.E. 1981. BiologyofInsectEggs.Pergamon
Press, Oxford.
upper portion ofthe cap. In the future, eggs
Johnson,C.G. 1936. ThebiologyofZ,c/>/o/'iriar/io-
ofother Corythiicha species need to be ex- dodendri Horvath (Hemiptera, Tingitidae), the
amined in order to determine the morpho- rhododendronlacebug.AnnalsofAppliedBiology
logical differences and similarities. These 23: 342-368.
data may provide important taxonomic in- Livingstone,D.andM. H.S. Yacoob. 1986. Natural
enemies and biologies of the egg parasitoids of
formation.
TingidaeofsouthernIndia.UttarPradeshJournal
Acknowledgments ofZoology 6: 1-21.
1987. BiosystematicsofTingidaeonthebasis
.
Appreciation is extended to R. C. ofthebiologyandmicromorphologyoftheireggs.
Froeschner, Department of Entomology. Proceedings of the Indian Academy of Sciences
96: 587-611.
Smithsonian Institution, for identifying the Morrill, A. W. 1903. Notes on the immature stages
adult specimens of Corythiicha arcuata. ofsometingitids inthegenusCorythiicha. Psyche
Thanks are due to J. Tisdale for typing the 10: 127-134.
manuscript. This is paper No. PS8050 of Ncal. J. W., Jr. and L. W. Douglass. 1988. Devel-
the Mississippi Agricultural and Forestry opment,ovipositionrate,longevityandvoltinism
of Slephanitis pyrioides (Heteroptera: Tingidae),
Experiment Station. Partial support forthis
anadventivepestofazalea,atthreetemperatures.
researchcamefrom NSFGrant DIR900143. Environmental Entomology 17: 827-830.
Neal, J. W.. Jr.. R. H. Haldemann. and T. J. Henn,'.
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