Comparative Study Of Mouthparts Of Three Species Of Horse Flies Of The Tribe Pangoniini Of Chilean Distribution (Diptera: Tabanidae)

Abstract

Mouthparts of 3 species representing Esenbeckia Rondani, Protodasyapha Enderlein, and Veprius
Rondani of the tribe Pangoniini were examined by scanning electron microscopy (SEM), and their
structures are herein described. The female of Esenbeckia (P.) fascipennis have mouthparts similar
to those found in species of haematophagous tabanids such as Scaptia (Pseudoscione). The male of
Esenbeckia (P.) fascipennis, and both sexes of P.(P.) hirtuosa, and V. presbiter exhibit mouthparts
with abundant micropilosity without teeth and microteeth that suggests a non-haematophagous,
nectarophagous feeding habit for these species.

Full text

579
Accepted by N.L. Evenhuis: 9 Jul. 2004; published: 21 Jul. 2004 1
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Copyright © 2004 Magnolia Press
Zootaxa 579: 1–15 (2004)
www.mapress.com/zootaxa/
Comparative study of mouthparts of three species of horse flies of
the tribe Pangoniini of Chilean distribution (Diptera: Tabanidae)
CHRISTIAN R. GONZÁLEZ1 & PAOLA FLORES2
1. Instituto Entomología, Universidad Metropolitana de Ciencias de la Educación, Casilla 147, Santiago,
Chile. Email: cgonza@umce.cl
2. Facultad de Ciencias Silvoagropecuarias, Universidad Mayor.
Table of contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
General description of structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Esenbeckia (P.) fascipennis (Macquart) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
MALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
FEMALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Protodasyapha (P.) hirtuosa (Philippi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
MALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
FEMALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Veprius presbiter (Rondani) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
MALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
FEMALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Literature cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Abstract
Mouthparts of 3 species representing Esenbeckia Rondani, Protodasyapha Enderlein, and Veprius
Rondani of the tribe Pangoniini were examined by scanning electron microscopy (SEM), and their
structures are herein described. The female of Esenbeckia (P.) fascipennis have mouthparts similar
to those found in species of haematophagous tabanids such as Scaptia (Pseudoscione). The male of
Esenbeckia (P.) fascipennis, and both sexes of P.(P.) hirtuosa, and V. presbiter exhibit mouthparts
with abundant micropilosity without teeth and microteeth that suggests a non-haematophagous,
nectarophagous feeding habit for these species.
Key words: Pangoniinae, Pangoniini, morphology, mouthparts, feeding, Chile

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ZOOTAXA Introduction
The Tabanidae comprise an important and well-represented family with than more 4,600
species described in all zoogeographic regions (Fairchild & Burger 1994). Hematophagy
in the females of many species can cause transmission of various diseases to humans and
other animals (Krinsky 1976). The importance of the Diptera in the origin of coevolution-
ary relationships of the Angiospermae with insects has been cited as significant, because at
least two-thirds of the living angiosperm species are insect pollinated (Labandeira 1998;
Ren 1998). Also Diptera, after the Hymenoptera, are very important for the pollination of
plants (Larson et al. 2001), especially where Hymenoptera are scarce (Grimaldi 1999) or
are the predominant group, such as in Andean habitats (Arroyo et al. 1982).
It is postulated that the Brachycera probably arose in the Triassic with a relatively
rapid diversification in different infraorders in the mid-Cretaceous, coincident with the
radiation of angiosperms (Yeates 2002). Mostovski et al. (2003) indicate that the appear-
ance of the tabanids occur in the Early Cretaceous jointly with other families of Diptera
with hematophagous species. However, Martins-Neto (2003) suggests that haematophagy
would have originated in tabanids of the Lower Cretaceous and could have started in trop-
ical regions later than the mid-Cenozoic. This hypothesis differs that by Downes (1971)
that the primitive forms of tabanids would be hematophagous and derived nectarophagous
forms. Nevertheless, as indicated by Lukashevich & Mostovski (2003), palaeontological
data on the initial phase of the Diptera evolution are scarce and insufficient for drawing
conclusions about a plesiomorphic diet for this group.
The Pangoniini in the Neotropical Region includes 13 genera (Fairchild & Burger
1994), 6 of which occur in Chile (Coscarón 1976; Coscarón & González 1991). The gen-
era present in Chile, according to Fairchild (1969), would include the most primitive forms
represented by small tabanids with short and fleshy proboscides, and show a tendency for
the flagellomeres to become fused into a basal flagellomere and with broad frons and
development of a basal callus. Fairchild (op.cit.), indicates that the Pangoniini corresponds
to the most primitive tribe in the Pangoniinae. Colless & McAlpine (1991) indicate that
females of the Australian species of Pangoniini have atrophied mandibles and that they
would live on the herbaceous vegetation of the forest.
Within the Neotropical Pangoniinae, females of several species of Scionini are known
to be hematophagous, although they also have nectarophagous habits (Coscarón &
González 2001). The known species of Mycteromyiini and Scepsidini are exclusively
nectarophagous (Coscarón & Philip 1979). However, within the Pangoniini, some species
of Esenbeckia are hematophagous (Wilkerson & Fairchild 1983), whereas species of Apa-
tolestes Williston and Stonemyia Brennan are exclusively nectarophagous (Middlekauff &
Lane 1980). Biological information for the adults of other taxa is absent.
The structure of tabanid mouthparts and its relation to the nutritional habit of the
adults has received little study. Although recently it has been suggested that it would be
taxonomically useful to differentiate taxa (Fang et al. 1999; McKeever & French 1999), as

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for other families of Diptera (Ceratopogonidae, Psychodidae, Cuterebridae), in which dif-
ferent structures (head, wings, abdomen) are highly similar, the study of the mouthparts
can be a very useful tool (McKeever et al. 1991; McKeever et al. 1997; Ronderos 1998;
Silva & Grunewald 2000; Fernández & Linardi 2002). For Chilean species, studies have
been conducted on Scaptia (Pseudoscione) (González & Sanhueza 2003) and Chaetopal-
pus annulicornis Philippi (González et al. in press). They concluded that according to the
morphology of the mouthparts, the species of S. (Pseudoscione) are hematophagous,
whereas C. annulicornis is exclusively nectarophagous.
The objective of this work is to describe the mouthpart morphology of 3 species of
Pangoniini, using scanning electron microscopy, and to relate this to possible feeding hab-
its.
Material and methods
Ten specimens of each sex were used for SEM studies. The following species were exam-
ined: Esenbeckia (P.) fascipennis (Macquart), Protodasyapha (P.) hirtuosa (Philippi) and
Veprius presbiter Rondani. The methodology followed for the dissection, preparation and
obtaining of the photomicrographs is similar to that described by González & Sanhueza
(2003). The mouthparts were described and characterized using the following characters:
1. Mandibles: a) total length; b) greatest width; c) presence of apical tooth; d) presence
of marginal teeth
2. Lacinia: a) total length; b) greatest width; c) Presence of teeth; d) micropilosity
3. Labrum: a) total length; b) greatest width; c) Presence of apical microteeth; d) pres-
ence of microtrichiae and micropilosity
4. Hypopharynx: a) total length; b) greatest width; c) ornamentation
Results
General description of structures
Mandibles: Paired structure, sclerotized. Dorsal and ventral surface without teeth or
another type of ornamentation. Medial and lateral margin with uniform teeth, and with evi-
dent apical tooth. Apical region pointed for the species studied. Only the female of Esen-
beckia (P.) fascipennis has mandibles.
Lacinia: Stylet thin, sclerotized. Dorsal surface concave, ventral convex. Dorsomedial
and dorsolateral surfaces, and sometimes the apex, covered by a different amounts of
micropilosity, depending on the species. The female of E. (P.) fascipennis only with
pointed, triangular teeth; the male is without these teeth, having triangular spicules instead.
Labrum: Flat, extended structure and sclerotized, wider in its proximal connection
with the head, thinning distally; apex blunt or pointed; microtrichiae present. Apical

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ZOOTAXA microteeth absent in P.(P.) hirtuosa and V. presbiter, present only in the female of E. (P.)
fascipennis.
Hypopharynx: Moderately sclerotized and with a tubular structure.. The opening of
salivary duct in the distal area formed by 2 cuticular extensions in the center of its upper
surface. Only the male of P.(P.) hirt uos a with sparse apical micropilosity; the apex blunt or
pointed.
Esenbeckia (P.) fascipennis (Macquart)
MALE
Mandibles: Absent.
Lacinia: (Fig. 1) Total mean length = 1,354 µm (1.354 mm) (n = 10). Greatest mean
width = 59.5 µm (n = 10). Apex rounded. Dorsal surface without teeth, and with abundant
and uniform micropilosity, replaced towards the apex by triangular spicules approximately
8-10 um, oriented cross-sectionally to its base. Ventral surface with short micropilosity,
uniformly distributed to the apex.
Labrum: (Fig. 2) Total mean length = 1,440 µm (1.440 mm) (n = 10). Greatest mean
width = 178 µm (n = 10). Dorsal surface with abundant micropilosity, medially intermin-
gled with short microtrichiae increasing in number when approaching the apex; proxi-
mally with smaller microtrichiae, without apical microteeth. Ventral surface with abundant
micropilosity along the edges, center smooth.
Hypopharynx: (Fig. 3) Total mean length = 1,658 µm (1.658 mm)(n = 10). Greatest
mean width = 155 µm (n = 10). Apex acute. Dorsal surface smooth, opening of salivary
duct approximately 140 um before the apex, without micropilosity on its interior or mar-
gins. Apex without micropilosity or other ornamentation. Ventral surface bare.
FIGURES 1–3. Esenbeckia (P.) fascipennis, male. 1, dorsal view of laciniae; 2, dorsal view of
labra; 3, ventral view of hypopharynx. Scale bars 1, 2: 10 µm; 3: 100 µm

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FEMALE
Mandibles: (Fig. 4). Total mean length = 1,927 µm (1.927 mm)(n = 10) Greatest
mean width = 206 µm (n = 10). Medial and lateral margin with developed curved, pointed
and triangular teeth, although more developed on the medial margin. Lateral marginal
teeth oriented toward the mandibular insertion. Apex with apical teeth pointed and
inclined slightly towards the medial margin. Ventral and dorsal surface bare.
FIGURES 4–7. Esenbeckia (P.) fascipennis, female. 4, mandible; 5, dorsal view of laciniae; 6, dor-
sal view of labra; 7, ventral view of hypopharynx. Scale bars 4, 6: 10 µm; 5, 7: 100 µm

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ZOOTAXA Lacinia: (Fig. 5). Total mean length = 1,636 µm (1.636 mm) (n = 10). Greatest mean
width = 72.3 µm (n = 10). Apex of the dorsal surface with 3-12 teeth, flattened apically
and more erect proximally, retrorse. Dorsolateral surface with long, uniform and abundant
micropilosity. Dorsomedial surface, distal to the apical teeth, bare. Ventral surface bare.
Labrum: (Fig. 6). Total mean length = 1,656 µm (1.656 mm) (n = 10). Greatest mean
width = 268.8 µm (n = 10). Apex blunt. Dorsal surface with abundant and short microtri-
chiae, arranged in horizontal rows; medially swollen, convex and bare. Apex with flat-
tened and triangular apical microteeth and circular depressions. Ventral surface with sparse
micropilosity distributed along the margins. Smooth central area, with short, uniformly
spaced micropilosity.
Hypopharynx: (Fig. 7). Total mean length = 1,637 µm (1.637 mm) (n = 10). Greatest
mean width = 143, 1 µm (n = 10). Apex acute. Without micropilosity or other ornamenta-
tion. Dorsomedial surface smooth, bare; salivary duct opening approximately 170 m
before the apex. Ventral surface rugose, bare.
Protodasyapha (P.) hirtuosa (Philippi)
MALE
Mandibles: Absent.
Lacinia: (Fig. 8). Total mean length = 60 µm (n = 10). Greatest mean width = 49 µm
(n = 10). Dorsomedial surface totally covered with abundant micropilosity oriented
towards the apex; apex acute, without teeth. Ventral surface bare, without teeth.
FIGURES 8–10. Protodasyapha (P.) hirtuosa, male. 8, dorsal view of laciniae; 9, dorsal view of
labra; 10, ventral view of hypopharynx. Scale bars: 10 µm.
Labrum (Fig. 9). Total mean length = 462 µm (n = 10). Greatest mean width = 83.4
µm (n = 10). Dorsal surface with longitudinal swelling, approximately to within 30 µm of

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the apex, with a smooth, bare region, laterally with microtrichiae oriented towards the
apex, diminished in number near the margins and apex, replaced by long and abundant
micropilosity. Apex acute with long micropilosity, and without microteeth. Ventral surface
smooth, with long and sparse micropilosity along the margin; bare medially.
Hypopharynx: (Fig. 10). Total mean length = 549 µm (n = 10). Greatest mean width
= 90.8 µm (n = 10). Apex acute, with sparse micropilosity. Dorsal surface smooth, salivary
duct opening approximately 100 um before the apex, sides straight. Ventral surface
smooth.
FEMALE
Mandibles: Absent.
Lacinia: (Fig. 11). Total mean length = 763 µm (n = 10). Greatest mean width = 65.3
µm (n = 10). Apex rounded, without teeth. Dorsal surface totally covered by abundant,
uniform micropilosity, oriented medially and toward the apex. Ventral surface bare.
Labrum: (Fig. 12). Total mean length = 536.1 µm (n = 10). Greatest mean width =
111 µm (n = 10). Dorsomedial surface with evident swelling that is flattened approxi-
mately 35 um before the apex. Microtrichiae of the dorsal surface sparse, more abundant
towards the apex. Apex acute, lateral edges with long, abundant micropilosity oriented
toward the apex, without microteeth. Ventral surface bare medially.
Hypopharynx: (Fig. 13). Total mean length = 659 µm (n = 10). Greatest mean width
= 84.4 µm (n = 10). Apex acute. Dorsal surface smooth, bare. Salivary duct opening
approximately 200 µm before the apex, without microtrichiae or micropilosity. Ventral
surface smooth, bare.
FIGURES 11–13. Protodasyapha (P.) hirtuosa, female. 11, dorsal view of laciniae; 12, dorsal view
of labra; 13, ventral view of hypopharynx. Scale bars 11, 12: 10 µm; 13: 100 µm.

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ZOOTAXA Veprius presbiter (Rondani)
MALE
Mandibles: Absent.
Lacinia: (Fig.14). Total mean length = 571 µm (n = 10). Greatest mean width = 60 µm
(n = 10). Apex blunt, without teeth. Dorsal surface with abundant micropilosity covering
the entire surface to the apex. Ventral surface smooth, bare.
Labrum: (Fig. 15). Total mean length = 679.5 µm (n = 10). Greatest mean width =
100 µm (n = 10). Apex blunt and trifid, without microteeth. Dorsal surface medially bare
with little medial swelling; microtrichiae long and thin, and more abundant toward the
margins, where they are intermingled with abundant micropilosity that extends to the apex.
Ventral surface smooth, bare.
Hypopharynx: (Fig. 16). Total mean length = 691 µm (n = 10). Greatest mean width
= 105.5 µm (n = 10). Apex rounded, without micropilosity. Opening of salivary duct
approximately 130 µm before the apex, without microtrichiae or micropilosity. Ventral and
dorsal surface smooth, bare.
FIGURES 14-16. Veprius presbiter, male. 14, dorsal view of laciniae; 15, dorsal view of labra; 16,
ventral view of hypopharynx. Scale bars 14, 15: 10 µm; 16: 100 µm.
FEMALE
Mandibles Absent.
Lacinia: (Fig. 17). Total mean length = 575 µm (n = 10). Greatest mean width = 70
µm (n = 10). Apex rounded. Dorsal surface without teeth, entirely covered with abundant
and uniform micropilosity, abruptly diminishing in size toward the apex. Ventral surface
smooth, bare.
Labrum: (Fig. 18). Total mean length = 590.5 µm (n = 10). Greatest mean width =
154 µm (n = 10). Apex blunt, without microteeth. Dorsal surface rough, with a medial

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swelling. Microtrichiae abundant, long and thin, directed medially and apically, forming a
column when united, bare proximally; without marginal micropilosity. Ventral surface
smooth, bare.
Hypopharynx: (Fig. 19). Total mean length = 604.5 µm (n = 10). Greatest mean
width = 110 µm (n = 10). Apex acute. Dorsal surface smooth, bare; salivary duct opening
approximately 200 µm before the apex, without microtrichiae and micropilosity. Ventral
surface smooth, bare.
FIGURES 17-19. Veprius presbiter, female. 17, dorsal view of laciniae; 18, dorsal view of labra;
19, ventral view of hypopharynx. Scale bars: 10 µm.
Discussion and conclusions
The main element of proboscis involved in the biting is the mandibles (Downes 1971).
This element is represented in the females of 8 families of Nematocera and 3 of Brachyc-
era (McAlpine 1981; Colless & McAlpine 1991). Usually the males, in species where the
females have functional mandibles, have mandibles vestigial or absent (McAlpine et al.
1981). The presence of developed mandibles armed with marginal teeth has been related to
cutting the skin of the hosts (vertebrate). This morphology is represented in haematopha-
gous forms (Silva & Grunewald 2000; Lukashevich & Mostovski 2003). Mandibles
reduced in size and with vestigial marginal teeth, replaced by micropilosity or absent,
would suggest the loss of the haematophagous habit (Downes 1971).
The females of 2 of the studied species, P.(P.) hirtuosa and V. presbiter, have no man-
dibles. Only the female of E. (P.) fascipennis has mandibles. The other mouthparts are well
developed in the 3 species, although they present modifications in the form of the apex and
the degree of micropilosity of the lacinia and the labrum. The hypopharynx has sparse
variation in shape and micropilosity (observed only in the male of P.(P.) hirtuosa). There
are no microtrichiae or micropilosity along the margins or within salivary duct (Table 1).

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ZOOTAXA Thus, the morphology of mouthparts of this species, except the female of E. (P.) fascipen-
nis, suggests an exclusively nectarophagous feeding habit.
This observation is also supported by the morphology of lacinia and labrum of E.(P.)
fascipennis female, which are very different from the other species. The lacinia exhibits
variation in morphology between the sexes of all species, but is accentuated in E. (P.) fasc-
ipennis. The quite similar morphology in general terms and the ornamentation of lacinia of
both sexes of P.(P.) hirtuosa and V. presbiter and of the male E.(P.) fascipennis (triangular
spicules), characterized by an abundant micropilosity, and also present in the non-hae-
matophagous males of the tribes Heteromyiini and Sphaeromiini (Ceratopogonidae)
(McKeever et al. 1991) and the absence of teeth, would suggest a nectarophagous feeding
habit, by its inability to penetrate the skin of hosts and acting only as part of the nutritional
channel of the proboscis (McKeever et al. 1997). The presence of retrorse teeth, like those
present in the female of E.(P.) fascipennis and the female of Scaptia (Pseudoscione)
(González & Sanhueza 2003), Tabanus Linneaus (Stoffolano & Yin 1983) and other fami-
lies of Diptera (Silva & Grunewald 2000), has been associated with a haematophagous
feeding habit, since these teeth separate and anchor to the epidermis to reach the dermis of
the hosts, allowing penetration of the mandibles. Stoffolano & Yin (1983) have suggested
that the action of lacinia during biting would only be mechanical. No sensilla have been
found like those present in the mandibles of haematophagous species of Tabanidae, Culi-
cidae and Simuliidae.
Differences are observed in the form of the apex, and the abundance and size of
microtrichiae in the labrum of P.(P.) hirtuosa and V. presbiter, and between both sexes of
these species, (Table 1). However, the labrum of both sexes of E. (P.) fascipennis is very
different from the other species. The female of E. (P.) fascipennis has abundant, short api-
cal microteeth, microtrichiae and lacks dorsal micropilosity, characters that are correlated
with the haematophagous habit. The male lacks apical microteeth and has sparse microtri-
chiae and abundant micropilosity. Apically, there are circular depressions that have been
postulated in Tabanidae to be chemoreceptors (Stoffolano & Yin 1983). Nevertheless, the
specific stimulus to which these structures respond has not been determined. The unknown
function and specificity of these receptors also pertains to Psychodidae (Silva &
Grunewald 2000). The size of this structure in P. (P.) hirtuosa (500 µm mean length) is the
shortest of the species studied, whereas E. (P.) fascipennis (1,550 µm mean length and 200
µm mean width) has the highest value. V. presbiter labrum has an average 635 µm length
and 127 µm width. The presence of identical labral muscle groups in males and females of
tabanids, suggests both sexes are able to manipulate this structure in a similar way during
feeding, independently of feeding characteristics (Bonhag 1952). The abundant dorsal
micropilosity and absence of apical microteeth of all the species, except the female of
E.(P.) fascipennis suggests, for these species, a nectarophagous feeding habit.

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TABLE 1: Summary of the morphological characteristics of the mouthparts of the male and the female of the
studied species. (D/A = distance of opening of the salivary duct, until the apex of the hypopharynx).
SPECIES MANDIBLES LACINIA LABRUM HYPOPHARYNX D/A
E.(P.) fascipennis Absent Abundant and uni-
form micropilosity.
Without teeth, with
triangular spicules.
Apex rounded
Abundant micropi-
losity. Microtri-
chiae scarce.
Apical microteeth
are not observed.
Apex acute
Without
micropilosity.
Apex acute
140 µm
Serrated in
both margins
and with api-
cal teeth
Abundant and long
dorsolateral micro-
pilosity.
Teeth present, flat-
tened and erect
Dorsal micropilos-
ity absent. Microt-
richiae abundant
and short. Apical
microteeth flat-
tened. Apex blunt
Without
micropilosity.
Apex acute
170 µm
P.(P.) hirtuosa Absent Abundant and long
micropilosity.
Without teeth.
Apex acute
Long and abundant
dorsal micropilos-
ity. Microtrichiae
scarce. Without
apical microteeth.
Apex acute
With sparse
and long apical
micropilosity.
Apex acute
100 µm
Absent Abundant and long
micropilosity.
Without teeth.
Apex rounded
Long and abundant
dorsal micropilos-
ity, only in the mar-
gins.
Microtrichiae
scarce. Without
apical microteeth.
Apex acute
Without
micropilosity.
Apex acute
200 µm
V. presbiter Absent Abundant and long
micropilosity.
Without teeth.
Apex blunt
Abundant dorsal
micropilosity only
in the margins.
Microtrichiae
scarce, long and
thin. Without apical
microteeth. Apex
blunt trifid
Without
micropilosity.
Apex rounded
130 µm
Absent Long and abundant
micropilosity.
Without
teeth.
Apex rounded
Dorsal micropilos-
ity marginal absent.
Microtrichiae
abundant, long
and thin. Without
apical microteeth.
Apex blunt
Without
micropilosity.
Apex acute
200 µm

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ZOOTAXA The hypopharynx shows little morphological variation between species and sexes, the
only observed differences being the form of the apex and the distance of the opening of the
salivary duct relative to the apex, greater in the females of P.(P.) hirtuosa and V. p re sbit er
(200 µm). Stoffolano & Yin (1983) indicate that in the female of T. nigrovittatus Macquart,
a hematophagous species, the salivary duct opens next to the apex, similar to Scaptia
(Pseudoscione) (González & Sanhueza (2003), also hematophagous, where the distance of
the opening of the salivary duct to the apex varies from 1 to 10 µm. In the species studied,
the distance is greater than 100 µm, suggesting a nectarophagous habit. The particular sit-
uation of the female of E. (P.) fascipennis (distance duct/apex 170 µm) could indicate a
lack of specialization or a dual function to feed on both blood and nectar since the main
structures for biting are equipped to cut the skin and to feed on blood.
The abundant micropilosity present on the labrum and lacinia of both sexes of P. ( P.)
hirtuosa and V. presbiter and the male of E. (P.) fascipennis could be related to an increase
in the efficiency for obtaining nectar, as observed in glossae of Colletidae (Hymenoptera;
Apoidea) (McGinley 1980; Laroca et al. 1989), that exhibit abundant and specialized
pilosity and an exclusively nectarophagous feeding habit. It also occurs in nectarophagous
flies, such as Bombyliidae (Szucsich & Krenn 2002).
The capacity to feed on blood is a relatively rare habit in insects. There are few orders
of insects in which this feeding habit is important such as Phthiraptera (lice), Heteroptera
(bugs), Siphonaptera (fleas) and Diptera (flies). In other, haematophagy occurs sporadi-
cally, such as, Noctuidae (Lepidoptera) y Menoponidae (Phthiraptera: Amblycera) (Luka-
shevich & Mostovski 2003). This feeding habit is primarily for obtaining protein
necessary for the maturation of eggs or, additionally, to obtain energy for daily activities.
Some species of haematophagous flies complete one gonotrophic cycle without taking
blood, a process called autogeny (Charlwood & Rafael 1980), but blood is absolutely
indispensable for a second or subsequent gonotrophic cycle.
If we assume the presence of mandibles as a determinant for a haematophagous feed-
ing habit, and analyzed the information available, for example, for the Pangoniinae, we
observe that the mandibles can be present or absent: present in Apatolestes Williston,
Esenbeckia Rondani (although in Apatolestes, and some Nearctic species of Esenbeckia
mandibles are apparently no functional and are unable of penetrating the skin of potential
hosts), Philoliche Wiedemann, Fidena Walker, Scaptia Walker, absent in Asaphomyia
Stone, Mycteromyia Philippi, Chaetopalpus Philippi, with marginal teeth developed (Apa-
tolestes, Philoliche, Scaptia), with marginal teeth small (Esenbeckia) or with marginal
teeth absent (Pangonius Latreille, Goniops Aldrich) and with an apical tooth (Apatolestes,
Esenbeckia, Philoliche, Scaptia). This variation suggests the diet, at least in the Pangonii-
nae, and also in other tabanid subfamilies is variable and specialized. According to Luka-
shevich & Mostovski (2003), haematophagy is a habit that has been developed
independently, and at different times, being preceded by different trophic and morphologi-
cal specializations. In the Tabanidae, nectarophagous forms are ancestral, from which hae-

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matophagous forms have evolved. Nectarophagous species of Pangoniini are most
plesiomorphous, according to their external morphological characteristics and male geni-
talia (Fairchild 1969). The nectarophagous habit in derived species such as Tabanus Lin-
naeus, is secondarily evolved from haematophagous species (J.F. Burger personal
communication).
Acknowledgements
To J.F. Burger (University of New Hampshire, USA) for reviewing the manuscript and for
help in editing the English version. Work supported by Dirección de Investigación, Uni-
versidad Metropolitana de Ciencias de la Educación Project DI/02/04/2002.
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