Sphingidae

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 Dilophonotini 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:

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.