A larva with peculiar very long pubescence on the integument, the pupa of Cryptotylus unicolor, and the larva and pupa of Tabanus nebulosus ornativentris are described and illustrated.Facultad de Ciencias Naturales y Muse

Coscarón, Cecilia Laura

Coscarón, Sixto

Mancebo, O. A.

Memórias do Instituto Oswaldo Cruz

English

El Servicio de Difusión de la Creación Intelectual

91Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 93(1): 91-97, Jan./Feb. 1998
The Preimaginal Stages of Cryptotylus unicolor
(Wiedemann) and Tabanus nebulosus ornativentris Kroeber
(Tabanidae-Diptera-Insecta)
S Coscarón/+, OA Mancebo*, CL Coscarón-Arias**
Facultad de Ciencias Naturales y Museo, 1900, La Plata, Argentina *Centro de Diagnóstico e Investigaciones
Veterinarias (CEDIVEF), 3600 Formosa, Argentina **Facultad de Ciencias Agrarias, 8324 Cinco Saltos,
 Río Negro, Argentina
A larva with peculiar very long pubescence on the integument, the pupa of  Cryptotylus unicolor, and
the larva and pupa of  Tabanus nebulosus ornativentris are described and illustrated.
Key words: description  -  larva and pupa  -  Neotropical horseflies
The female pupa was the only known
preimaginal stage of Cryptotylus unicolor (Coscarón
& Poi de Neiff 1996). From larvae collected on Pistia
stratiotes (repollito de agua) in lagoons of Chaco
geographic area, we obtained mature larvae, pupae
and imagoes of both sexes of C. unicolor. From the
same place we collected another larva that changed
to the pupa stage in the laboratory, emerging finally
as a female corresponding to Tabanus nebulosus
ornativentris. This taxon was considered a subspe-
cies due to morphological and tinctorial differences
with the typical T. nebulosus DeGeer that has a north-
ern distribution (from Belize to Surinam and Mato
Grosso). The subspecies ornativentris is restricted
to the Chaco area in Paraguay, Bolivia and northern
Argentina. The pupa of T. nebulosus described by
Goodwin and Murdoch (1974), originated from
Panama in the typical area of nebulosus s. str. is
found. Because the pupae collected by us showed
some differences from the pupa collected in Panama
we include here a description of the pupa of T. n.
ornatriventris as well as the previously unknown
larva.
MATERIALS AND METHODS
Specimens were collected in Formosa province,
in ponds around CEDIVEF (Centro de Diagnóstico
e Investigaciones Veterinarias, Formosa) south of
Formosa City on Highway 14. Larvae were found
living on water lettuce, Pistia stratiotes. Live ma-
terial was maintained individually in vials, with
humid cotton until pupation, and subsequent emer-
gence of imagoes. For morphological studies, lar-
vae were fixed in boiling water and stored in 70%
ethanol. Larvae and pupae were examined with
stereoscopic microscope. C. unicolor larvae were
fixed in glutaraldehyde for scanning electron mi-
croscope studies. Exuviae of larvae were mounted
on slides for compound microscopic studies. Speci-
mens are in the Museo La Plata collection.
RESULTS
Cryptotylus unicolor
Mature larva: robust (relaxed 20 mm, fixed 30
mm long). Color in life grayish green, lighter ven-
trally, tegumental ornamentation with longitudinal
pale striations of variable intensity on the different
specimens, showing dorsally one median and 1+1
submedian, 2+2 laterally, and ventrally 1+1 subme-
dian (Fig. 1). Integument with abundant pubescence
constituted by long ciliae (0.06-0.08 mm), arranged
in differing shapes from subtriangles to subquadrates
0.1-0.16 mm wide (Figs 6, 9-14). Head capsule yel-
low brown, length 2.6 mm. Antennae with the third
article 0.35-0.40 times longer than the second (Figs
2, 3); mandible length 1.5 mm with 21-23 ser-
rulations; maxillae, clypeus, labrum and prementum
as shown in Figs 2-5. Thoracic segments with 4-
6+4-6 trichomes each 0.4-0.5 mm long and bearing
one to three branches emerging from the base (Figs
2, 9). Tegumental longitudinal striations on the an-
terior third of the segment, separated by 0.0077-
0.023 mm. Abdominal segments II-VII with three
pairs of pseudopods: 2 dorsal, 1+1 lateral and 2 ven-
tral (Fig. 1); the dorsal pseudopodia on the first ab-
dominal segment appear fused; only the dorsal
pseudopods are well developed, the ventral
pseudopodia are small and the lateral pseudopodia
are inconspicuous. Pseudopod trichomes are vari-
able in size and shape, single to medio-distally and
divided in to 2-6 branches (Figs 6, 10), length 0.2-
0.35 mm. There are 14-16 abdominal trichomes on
each segment, length 0.5 mm. Anal segment (eigth
abdominal segment) 2.5-3.5 mm long; anal lobe
+Coresponding author. Fax: +54-21-257527
Received 14 July 1997
Accepted 1 October 1997
93Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 93(1), Jan./Feb. 199892 Preimaginal Stages of C. unicolor and T. n. ornativentris  S Coscarón et al.
Cryptotylus unicolor, larva. Fig. 1: general aspect (hd.: head, ha.: hair, ps.: pseudopodia, siph.: siphon, an. l.: anal lobes, 1-3:
thoracic segments, I-VIII: abdominal segments). Fig. 2: head partially enveloped (a.: antenna, cly.: clypeus, lab.: labrum, mx. p.:
maxillary palp, l. p.: labial palp, mdb: mandible). Fig. 3: antenna (a) and maxillary palp (mx. p.). Fig. 4: mandible and prementon.
Fig. 5: labrum and labial palp (p.). Fig. 6: spines of pseudopodia and group of ciliae of tegumental pubescence. Fig. 7: anal segment
and siphon (an. l.: anal lobe, a. fr.: anal fringe). Fig. 8: apex of siphon in lateral view. (Figs 2 and 7 with the same scale and also Figs
3, 5, 6 and 8 respectively).
Cryptotylus unicolor, larva (photographs). Fig. 9: trichome and groups of ciliae of tegument pubescence of thoracic segment, (tr.:
trichome). Fig. 10: general view of pseudopodia. Fig. 11: tegument pubescence groups bordered by stripes of longitudinal tegu-
ment striations. Fig. 12: tegument pubescence groups with high magnification. Fig. 13: anal segment in ventral view showing the
anal lobes. Fig. 14: siphon scarcely emerged in posterior view (tr.: trichome).
fringed with abundant pubescence 0.06-0.08 mm
long (Figs 7, 13). Respiratory siphon 0.9-1.1 mm
long, showing longitudinal striations, and 1+1 dor-
sal, 1+1 ventral, 1+1 medio lateral trichomes with a
group of 2-3 hairs inserted apically (Figs 8, 14); tra-
cheae relativeliy short 0.6-0.7 mm long.
Pupa: general aspect and morphology of fron-
tal plate, thoracic peritreme, and aster of female
as in Figs 15-19, male pupa not different from
female except for the anal segment; except for
11-17 dorso-lateral spines left and right respec-
tively and 18-28 ventrolateral spines on left and
right respectively (Fig. 20). Length of male aster
tubercles are: dorsal 0.5-0.7 mm, lateral 0.25-0.5
mm and ventral 0.2-0.4 mm. Variation in spine
number of anal segment in the female are: dorso-
lateral 13-19 and ventrolateral 12-18.
Material examined: six males and eleven females
reared in the laboratory from larvae collected on P.
stratiotes, in lagoons near Formosa city during Oc-
95Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 93(1), Jan./Feb. 199894 Preimaginal Stages of C. unicolor and T. n. ornativentris  S Coscarón et al.
Cryptotylus unicolor, pupa. Fig. 15: general aspect. Fig. 16: frontal plate in anterior view. Fig. 17: peritreme of thoracic spiracle.
Figs 18-19: anal segment of female in posterior and lateral view respectively. Fig. 20: anal segment of male in posterior view.
Tabanus nebulosus ornativentris- Figs 21-22 larva. Fig. 21: spines of anal lobe fringe. Fig. 22: spines of pseudopodia. Figs 23-28
pupa. Fig. 23: general aspect. Figs 24-25: frontal plate in anterior and ventral view respectively (as.: antennal sheats, ct.: callus
tubercle, ar.: antennal ridge, ft.: frontal tubercles). Fig. 26: peritreme of thoracic spiracle. Figs 27-28: anal segment of female in
lateral and posterior views respectively.
tober, November and December, col. O Mancebo.
Discussion: the abundant body pubescence,
plus the greenish gray coloration with longitudi-
nal light stripes, number and disposition of pseudo-
pods in larvae show a strong resemblance to
Chlorotabanus. This is reinforced by aspect of the
adults and demostrates the close relationships of
these two genera.
97Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 93(1), Jan./Feb. 199896 Preimaginal Stages of C. unicolor and T. n. ornativentris  S Coscarón et al.
Tabanus nebulosus ornativentris
Mature larva: (material observed in life and de-
scribed from exuvia). Large 33 mm. Uniformly
whitish, without strong contrasting colors, marked
with light grayish pubescent. In general aspect is
like T. claripennis (Bigot) but larger than this spe-
cies larvae (Coscarón & Led 1969). Third antennal
article 0.44-0.57 times longer than the second. Man-
dible 1.1 mm long with 12-13 serrulations. Thoracic
and abdominal segments with homogeneous, short
pubescence constituted of microtrichiae forming a
ring on the anterior border which is continued dis-
tally near the middle of the segment by thick stripes.
The remainder of the integument is bare with longi-
tudinal striations 0.007 mm wide. Abdominal seg-
ments show an anterior pubescent ring shorter than
in the thorax. Just behind the pubescent area, are
the pseudopods on the II-VII abdominal segments.
They have robust spines 0.6-0.7 mm length (Fig.
22). The pseudopods form a near continuous wide
ring on the anterior third portion of the segment.
The anal lobes were fringed by pubescence formed
of thin spines 0.6-0.7 mm length (Fig. 21). Traqueal
ducts 1.5 mm length.
Pupa female: 29 mm length, yellowish brown.
Tubercle callus sharply ridged 0.5 wide and 0.7
mm high above median cleft; frontal tubercles well
evident 0.5 mm long by 0.38 mm wide at the base,
pointed slightly apically, antennal ridge with two
prominent elevations apically and subacute 0.52
mm high. Antennal sheaths 0.75 mm long and 0.52
mm wide at base; antero and postero-orbital setae
emerging from a prominet tubercle; vertexal tu-
bercles well evident (Figs 24, 25). Thoracic spi-
racle with spiracular prominences well evident
showing hard curvature 1,1 mm length and 0,38
mm high over thorax surface (Fig. 26). First ab-
dominal segment distally bordered by a single
fringe of short spines; II-VII combs with bi or
triseriate longer spines. Tergite VII comb mostly
uniseriate with 41 spines relatively short and uni-
formly distributed with 1+1 median spines about
4-5 times longer and posteriorly dispossed; lateral
and ventral long spines are also present (Fig. 23).
Dorsolateral comb of preanal segment with 27-28
relatively short and robust spines on each side,
ventrolateral combs with 8-9 spines (Figs 27, 28);
dorsolateral and ventral tubercles of aster 0.33-
0.25-0.25 mm long respectively, no additional ac-
cessory pairs of tubercles on the midline.
Material examined: one female developed from
a mature larva to a pupa in the laboratory. The larva
was collected from Formosa, on P. stratiotes. The
same lagoons also support larvae of Myiotabanus
barrettoi, Lepiselaga (L.) crassipes, T. claripennis,
T. pungens and C. unicolor, collected by O
Mancebo.
Discussion: the T. nebulosus ornativentris pupa
examined showed some differences from the pu-
pal description of T. nebulosus by Goodwin and
Murdoch (1974). There are also differences in the
imagoes (Coscarón 1979) which are listed in Table.
The differences showed in the Table helps to
justify the existence of the subspecies ornativentris
from the southern area in accordance to Fairchild
and Burger (1994).
ACKNOWLEDGEMENTS
To Nélida R Caligaris for illustrations and CEDIVEF
personnel for help in the larvae collection work.
REFERENCES
Coscarón S 1979. Notas sobre Tabánidos Argentinos XV.
El género Tabanus Linnaeus (Diptera-Insecta). Obra
TABLE
Comparison of pupal and adult female differences of Tabanus nebulosus and T. n. ornativentris
Character T. nebulosus T. n. ornativentris
Pupa
Color Brown Yellowish brown
Antennal ridges elevation 0.46 mm 0.52 mm
Callus tubercles Smooth Sharply ridged (Fig. 24)
Thoracic spiracle length 1.3 mm 1.1 mm
VII tergite comb Biseriate, fringe of 42-46 spines Uniseriate, fringe of 41spines 4-5
times long and similar long spines
lateraly and ventrally (Fig. 23)
Number of preanal comb spines Dorso lateral: 25 27-28
ventral: 10-11 8-9
Tubercles of aster Relativelly thin Relativelly thicker (Figs 27, 28)
Lateral and ventral aster 0.50 and 0.33 mm respectivelly 0.25 and 0.25 mm
tubercles length
Accesory pairs of tubercles
along vertical midline of aster Present Absent
Female
Abdomen midline triangles of T. III-VI Lighter and scarcely evident Darker and more evident
Color of scutum pilosity Golden reddish brown Dark grayish brown
Prescutum spot Present Absent
Wing coloration Scarcely darkened and without Strongly darkened with pale
light spot subcircular spot on medial
anterior portion of M1 and
covering part of cells br and bm
del Centenario del Museo de La Plata 6: 251-278.
Coscarón S, Led JE 1969. Contribución al conocimiento
de Tabanus claripennis  (Bigot) con especial
referencia a la morfologia y biologia de sus estados
preimaginales. Analecta Veterinaria 1: 13-15.
Coscarón S, Poi de Neiff A 1996. The pupa of
Cryptotylus unicolor (Wiedemann) (Diptera-Taban-
idae). Rev Asoc Cien Nat Litoral 27: 65-68.
Fairchild GB, Burger JF 1994. A Catalogue of the Ta-
banidae (Diptera) of the Americas South of the
United States. Mem Am Entomol Inst (Gainesville)
55: vii+ 249 pp.
Goodwin JT, Murdoch WP 1974. A study on some
inmature. Neotropical Tabanidae (Diptera). Ann
Entomol Soc Am 67: 85-133, 42 pls.
98 Preimaginal Stages of C. unicolor and T. n. ornativentris  S Coscarón et al.


The Preimaginal Stages of Cryptotylus unicolor (Wiedemann) and Tabanus nebulosus ornativentris Kroeber (Tabanidae-Diptera-Insecta)

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The Preimaginal Stages of Cryptotylus unicolor (Wiedemann) and Tabanus nebulosus ornativentris Kroeber (Tabanidae-Diptera-Insecta)

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