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The
hawk-moths are among the most familiar and best known of Lepidoptera, both the
streamlined adults and the horned larvae, some of which bear a striking
resemblance to the head of a snake in both appearance and behaviour when
alarmed.
The adults fly by day, by night, or in the crepuscular period, many with long
tongues that have evolved in parallel with long, tubular corollas or nectaries
on the flowers they pollinate. Some of these species hover in front of the
flowers rather than settling on them, the only instance of hovering in the
Lepidoptera. Species of the genus Macroglossum Scopoli are known as 'hummingbird
hawks'.
The family is found worldwide, but is most diverse in the tropics e.g. four
times as many Neotropical species as Nearctic ones, and a similar relationship
between the Palaearctic fauna and the Afrotropical (approximately three times)
and Oriental (four times) faunas. The Australian fauna is made up mostly of
species in widespread Indo-Australian genera, but also has seven endemic genera,
some of which are associated with ancient elements of the flora such as
Proteaceae. There is a monotypic genus in New Caledonia, Compsulyx Holloway,
that may have a relationship with Neotropical taxa (see comment in D'Abrera
(1986)).
The work of Rothschild & Jordan (1903) is still the most detailed treatise
of the family as a whole, but the majority of species, including taxa described
since 1903, have been illustrated in the diagnostic summary of the world fauna
by D'Abrera (1986). Parts of the Oriental fauna have been described by Inoue
(1973; Taiwan), Diehl (1980; Sumatra), Dupont & Roepke (1941; Java) and Bell
& Scott (1937; the Indian Subregion). Recent works on the Bornean fauna are
by Holloway (1976) and Harman (1981), though these represent no more than
partial check lists.
Adults
Unlike other Bombycoidea, the Sphingidae have the tongue well developed as a
rule rather than as an exception, extreme length being exhibited by some
Sphingini. Processes on either side of the tongue, the pilifers, bear bristles
and provide some characters of use in the higher classification, as does the
genal plate, a triangular process between the pilifer and the eye.
The labial palps are usually large in most of the Macroglossinae, often reduced
in the Sphinginae, and again provide characters defining the groups in the
higher classification, particularly the patch of scales at the base of the first
segment.
The antenna is rarely bipectinate, usually rather swollen, tapering at the tip
which is often hooked. Rothschild & Jordan (1903) made a detailed analysis
of sphingid antennal structure.
The forewings are elongate, narrow, apically acute in many groups of genera. R2
and R3 have a common stalk, bifurcating at the distal extreme (some Smerinthini)
or being totally fused. The hindwings are very much shorter than the
forewings and indeed shorter than the abdomen, proportions that are seen also in
Notodontidae, Cossidae, and some Lasiocampidae, Noctuidae and Arctiidae where
the forewings are narrow.
The frenulum and retinaculum are usually present; reduction or loss are only
found in some genera of the Sphinginae and may be correlated with broader
forewings and less powerful flight.
The distal margins of abdominal segments are finely spined, but this is weaker
in many Sphinginae. The male genitalia have a strong uncus and gnathus, the
former, and sometimes the latter, often bifid in the Sphinginae and Dilophotini
but single and opposed by an upcurved, similar gnathus in most Macroglossinae.
Rothschild & Jordan (1903) regarded the former state as plesiomorphic. The
valves are usually simple, oval, with a strong saccular harpe.
The external surface of the valve has a slight rib subcostally that bears a
patch of modified scales; the 'friction-patch' of Rothschild & Jordan; in
the Macroglossinae
these are reduced to a row of long, conspicuous blade-like scales. The aedeagus
apex often has spined processes; the vesica is sometimes scobinate.
In the female genitalia the ductus seminalis arises from the ductus bursae; a
signum is sometimes present in the bursa copulatrix.
Eggs
The eggs are globular or slightly flattened, smooth, with only microscopical
structure (Rothschild & Jordan, 1903).
Larvae
The horned, cylindrical larva of the Sphingidae is probably one of the most
familiar amongst the Lepidoptera. The horn is dorsal on segment A8 as in other
Bombycoidea. It is reduced to a stump in final instars of many Macroglossinae, a
reduction comparable to that seen in other Bombycoidea such as the Brahmaeidae.
In the New World species Ceratomia amynthor Hubner there are paired thoracic
protruberances that again may be homologous with those of other bombycoids.
Secondary setae are present in many genera, usually as very short spines or
granulations, often lost after the first instar.
Pupae
Pupation is usually in the soil, sometimes quite deeply, sometimes in a
loose cocoon in leaf litter, rarely on a branch of the host-plant. The pupa has
a movable abdomen, often rolling and turning in its cell in the soil, and a
cremaster, variable in form but usually bifid. The tongue case is variable in
extent, sometimes projecting or free, slightly coiled, often in those genera
where the imaginal tongue is very long (e.g. Sphingini).
Higher classification
Today the Sphingidae are usually divided into two subfamilies, Sphinginae
and Macroglossinae, rather than the several recognised by Rothschild &
Jordan (1903), though the overall structure of the classification is similar
(Hodges, 1971; Derzhavets, 1984). The currently accepted system is as listed by
Derzhavets, and the Bornean genera are assigned to subfamilies and tribes as
follows:
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Sphinginae:
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Sphingini:
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Agrius, Megacorma, Acherontia, Meganoton, Psilogramma, Dolbina.
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Smerinthini:
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Amplypterus, Ambulyx, Clanis, Marumba, Daphnusa, Cypa,
Smerinthulus, Degmaptera, Callambulyx, Sataspes.
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Macroglossinae:
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Dilophonotini:
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Cephonodes
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Macroglossini:
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Gnathothlibus, Daphnis, Elibia, Acosmeryx, Gehlenia, Panacra,
Angonyx, Empinanga, Eurypteryx, Giganteopalpus, Macroglossum, Hippotion,
Theretra, Rhyncholaba, Rhagastis, Cechenena.
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The
last five genera of the Macroglossini form a closely knit subtribe, the
Choerocampina, in which the pilifer is long and twisted, with two distinct types
of bristle; the genal plate is very small (of larger than average in Macroglossum). The Choerocampina also lack scales on the interior of the second
segment of the labial palp.
Distinction of the two subfamilies is based on characters of both adults and
larvae, though it is not clear whether all of these represent apomorphic
(derived) states. Most of those listed below are discussed by Rothschild &
Jordan (1903) and Hodges (1971).
The Sphinginae lack the patch of scales seen at the base of the first segment of
the labial palp, in Macroglossinae. This is absent in other Bombycoidea but
present (or there are analogous structures) in other macrolepidopteran groups.
So it is unclear which is the apomorphic state. The Sphinginae also have reduced
hind-tibial spurs, stated to be a specialisation by Rothschild & Jordan,
especially in deeper-winged taxa (Smerinthini), though this may be a general
trend in the Bombycoidea. Some Smerinthini have reduced tongues, a full
complement of radial veins, and a bombycid-like resting posture, seen particularly in
Smerinthus and Daphnusa.
The Sphinginae larva is usually much more granulate or finely spinose, with
annular folding on each segment. The pattern on abdominal segments usually
consists of oblique pale bars laterally and above the spiracle on each segment,
and the larvae are thus predominantly cryptic.
In the Macroglossine the friction-patch on the valves of the male genitalia is
reduced usually to a row of long, blade-like scales, or is absent. The male
eighth abdominal sternite is usually unevenly sclerotised or modified (not so in
Sphinginae).
The macroglossine larva has longitudinal, linear patterning (though oblique bars
may also be present), is usually smooth, and often has the caudal horn reduced
to a stump in the final instar . The thoracic/abdominal junction zone is often
swollen, and in many genera some abdominal segments bear conspicuous subdorsal
eye-spots, particularly A1; the larva, when alarmed, bunches its anterior part
and exposes these 'eyes'. Thus, though generally cryptic, the larva has a second
line of defence as a snake-mimic if discovered. Snake-mimicry is also seen in
the Brahmaeidae and some Bombycidae.
Host-plant
relationships
The
host plant relationships of the family and its sections have already been
discussed in the introductory section. The two major tribes of the
Sphinginae and the Macroglossinae show little overlap in the families they
exploit as larval host-plants. The most important families utilised by each
group are listed in Table 2. The majority of records for the Sphingini
are from Bignoniaceae, Oleaceae, Verbenaceae and Solanaceae, those for the
Smerinthini are from Leguminosae, Fagaceae and Anacardiaceae, and those for the
Macroglossinae are from Araceae, Vitidaceae and Rubiaceae.
Single records (one or two records for Macroglossinae) from several other
families have been noted for the three groups as follows:
Sphingini: Annonaceae, Apocynaceae, Buxaceae, Cannabinidaceae, Cannaceae,
Casuarinaceae, Compositae, Cucurbitaceae, Dipterocarpaceae, Ehretiaceae,
Euphorbiaceae, Flacourtiaceae, Lauraceae, Rubiaceae, Tetragoniaceae.
Smerinthini: Apocynaceae, Dipterocarpaceae, Euphorbiaceae, Juglandaceae,
Lythraceae, Malvaceae, Meliaceae, Meliosmaceae, Rosaceae, Tiliaceae.
Macroglossinae: Amaranthaceae, Apocynaceae, Bignoniaceae, Chenopodiaceae,
Commelinaceae, Cruciferae, Cucurbitaceae, Daphniphyllaceae, Dioscoreaceae,
Hypoxidaceae, Naucleaceae, Passifloraceae, Pedaliaceae, Pontederiaceae, Rosaceae,
Saxifragaceae, Scrophulariaceae, Solanaceae, Tiliaceae, Urticaceae.
Thus the Bornean Sphingini are recorded from 28 families, the Smerinthini from
19 families and the Macroglossinae from 38 throughout their geographical range.
Geography and habitat preference
A high proportion of Sphingidae species, about one third, ranges widely,
through the Indo-Australian tropics, their distribution straddling Weber's Line
between Sulawesi and the Moluccas, the major discontinuity in the region. About
40% are widespread in the Oriental tropics but do not cross Weber's Line.
Species widespread in Sundaland are fewer, perhaps 20%. The only endemic species
are Panacra psaltria Jordan (Diehl's (1980) record from Sumatra is based on a
misidentification) and M. pseudungues sp. n.
The faunas of Sumatra (112 species) and Java (97 species) are comparable in
size to the Bornean total of 94. Inoue (1973) recorded a possible 67 species for
Taiwan.
The genera Polyptychus Hubner, Leucophlebia Westwood, Nephele Hubner and
Gurelca
Kirby are represented in Sumatra but have not yet been recorded from Borneo.
The tribe Smerinthini differs from the Sphingini and Macroglossinae in having a
predominance of Sundanian species (13), one fewer Oriental widespread species
(12), and only one species that crosses Weber's Line.
This
distinction between the Smerinthini and other groups is also seen in trends of
habitat preference (Holloway, 1976; 1984; in press). The family is most diverse
overall in lowland, open, agricultural, disturbed or secondary habitats, but
Smerinthini are not, tending to be taken more frequently in undisturbed
rainforest. The Sphingini and Macroglossinae also are taken in large numbers at
high altitude sites but are probably not resident there; they may migrate
upwards, hill-topping. Thus large catches of common lowland species were also
taken above 2000m on G. Kinabalu.
There are a few species that are predominantly montane in Borneo: Dolbina
krikkeni Roesler & Kuppers in the Sphingini; Marumba spectabilis Butler in
the Smerinthini; Gehlenia falcata Hayes, Giganteoalpus mirabilis Rothschild,
Macroglossum passalus Drury and Rhagastis castor Walker in the Macroglossinae.
Most species fly by night and come to light, but strongly only to a powerful
mercury vapour U.V. source. An exception to this is Daphnusa ocellaris Walker, a
species that seems to be abundant in the understorey of lowland rainforest and
comes to weaker light sources. The day-flying species of Sataspes, Cephonodes
and Macroglossum are not taken at light either.
A number of species are known to be migratory, all in the Sphingini and
Macroglossinae, and particularly in the genera Agrius, Cephonodes, Macroglossum,
Hippotion and Theretra.
Systematic account
Much of the morphological detail presented in the generic descriptions is
from Rothschild & Jordan (1903), where the reader may find a much fuller
description of generic features. The intention here is to highlight the
diagnostic features where possible, but the significance of these can only be
clarified by a modern phylogenetic review of the family.
Many species have numerous synonyms. Those names published prior to 1903 are
listed by Rothschild & Jordan (1903) and are not repeated here. Original
descriptions of Bornean or Sundanian subspecies and their synonyms are given..
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