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This
family is most diverse in the Oriental Region, but is recorded from all Old
World zoogeographic regions. The New World Apatelodidae have in the past been
regarded as Bombycidae but are now (Franclemont, 1973) considered distinct
though allied to the Bombycidae, Eupterotidae and Anthelidae. Apatelodidae
larvae tend to be hairy like those of the last two families, though one South
American genus, Colla Walker, has larvae similar to those of Bombycidae. The
relationships of the two families and their position within the Bombycoidea need
further investigation.
Adults
Oriental Bombycidae fall into two lineages on characters of wing venation
and male genitalia.
Figure
4. Venation in the two
lineages of the Bombycidae: left, Mustilia dierli; right, Ocinara
albiceps.
The
first, with vein CuP present in both wings and often a vestige of the M stem
present in the forewing cell, has all radial veins except R5 arising anteriorly
from Rs (Fig. 4); the sclerites of segment 8 in the male genitalia are strongly
modified. This group is typified by Bombyx Linnaeus, includes the Ocinara
complex and Gunda Walker in the Sundanian fauna and the mainland Asian Rondotia
Moore, and is also represented in Africa (the Ocinara group) and the Papuan
Subregion (the divergent genus Elachyophtalma Felder (= Laganda Walker), diverse
in New Guinea but also represented in the Moluccas and with one species in
Sulawesi).
The second lineage has CuP absent and only four radial veins of which the
posterior two arise posteriorly from Rs (Fig. 4); the M stem is not present in
the forewing cell; the eighth sclerites of the male abdomen are only slightly
modified. The lineage is typified by Mustilia Walker and includes Andraca
Walker
Prismosticta Butler, Oberthueria Staudinger and Pseudandraca Miyata. This group
is the subfamily Oberthuerinae of Kuznezov & Stekolnikov (1985).
The Australian genus Panacela Walker has been included in the Bombycidae in the
past but is now placed in a subfamily of the Eupterotidae (as discussed by
Fletcher & Nye (1982)). The forewing venation has one radial vein absent as
in Eupterotidae, and the configuration is generally concordant with that family,
though M3 and CuA1 share a long common stalk. The frenulum is present. The
larvae are densely hairy.
All Bombycidae have the dorsal zone of the hindwing pleated and often somewhat
concave; this pleated zone is the most heavily patterned part of the wing. This
feature is seen to some extent in Eupterotidae, especially Panacela. The
frenulum is present but very short, rather stout. The male antennae are
bipectinate throughout as are the somewhat shorter (relatively to wing length)
ones of the females in the Bombyx lineage. In the Mustilia lineage the female
antennae are much more weakly bipectiante (Prismosticta) or filiform (Mustilia,
Andraca). The eyes in Prismosticta are hairy (Miyata, 1970).
Bell (MS) illustrated the resting posture of a Gunda species that may be
characteristic for the Bombyx lineage. The wings are held out at right angles to
the body (though the abdomen may be flexed to one side), with the dorsal pleats
of the hindwing folded round onto the upper surface of the forewing.
In the male genitalia the uncus is usually bifid, though this state is
secondarily lost in some Andraca species and genera of the Ocinara group such as
Ocinara Walker itself and Trilocha Moore. The saccus is only strongly developed
in the Bombyx lineage where it is variably associated or even fused with the
bifid modification of the eighth sternite to form a joint structure reminiscent
of the cubile of some Lasiocampidae. The gnathus is strong but often divided in
members of the Mustilia lineage and strong in Bombyx, weak in Gunda, and lost in
some members of the Ocinara group.
No features of the female genitalia are diagostic for the family but there are
several of generic significance. Only Ocinara has a signum in the bursa in the
Bombyx lineage, but one is seen in two genera of the Mustilia lineage; in the
latter the ductus bursae exhibits a central spiral.
Eggs
The
eggs are variable in shape, usually rather flattened spheres, laid in clusters,
lines or 'walls', sometimes covered with abdominal scales from the mother.
Larvae
The most detailed illustrated account of larval morphology in bombycid
genera in both lineages is by Miyata (1970), who also illustrated adult and
pupal features. Other descriptions of larvae are by Sevastopulo in papers cited
in the systematic account and by Bell (MS).
The larva appears smooth, but is usually densely invested with small secondary
setae. All abdominal prolegs are present, with crochets in a homoideous
biordinal mesoseries. The thorax is swollen in some genera, particularly those
of the Bombyx lineage. There is usually a prominent horn in the centre of the
eighth abdominal segment, a feature common to both lineages. Paired thoracic
horns are not seen, but in Bombyx huttoni there are small paired horns on
abdominal segments 1 to 7 (preserved material in BMNH). The caudal horn is
strongest in members of the Mustilia group (Pseudandraca, Oberthueria) but
reduced to a hump in Andraca, also a member of the group. This group appears to
have a larval resting posture with anterior and posterior parts of the body
adjacently erect away from the substrate, a disruptive cryptic posture seen also
in some smooth, leaf-mimicking notodontid larvae.
Pupae
Pupation is in a densely silken cocoon, the quality and fineness of which in
Bombyx mori is the basis of the silk industry. The cremaster is rounded and
finely setose in most genera but more rugose and spined in Prismosticta;
Prismosticta also lacks sparse setae elsewhere on the pupa, present in other
genera.
Host-plant relationships
There are numerous records of members of the Bombyx lineage from genera of
the family Moraceae: Morus, Streblus, Ficus, Artocarpus. Miyata (1983) noted
Bombyx mandarina as feeding on Malus (Rosaceae) and Diospyros
(Ebenaceae) as
well as Morus in Japan but all tropical records are from Moraceae. The
Chinese Rondotia menciana Moore is also noted from Morus (Moore, 1885,
Ann. Mag.
Nat. Hist. (5), 15: 491).
Records for the Mustilia lineage are more diverse but there is predominance of
records from the related families Symplocaceae and Theaceae:
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Andraca albilunata:
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Cudrania
(Moraceae Sevastopulo (1940) as Cudranus)
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Andraca apodecta Swinhoe:
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Camellia
(tea; Theaceae; Roepke, 1924)
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Andraca bipunctata Walker:
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Symplocos (Symplocaceae; Sevastopulo (1946)); Camellia
(Roepke,
1924).
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Mustilia falcipennis Walker:
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Symplocos (Sevastopulo, 1946)
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Mustilia phaeopera Hampson:
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Camellia (Theaceae; Sevastopulo, 1940)
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Oberthueria falcigera Butler:
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Acer (Aceraceae; Miyata, 1983)
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Prismosticta hyalinata Butler:
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Symplocos (Miyata, 1983)
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Pseudandraca gracilis Butler:
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Stewartia (Theaceae; Miyata, 1983)
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Zoogeography
and habitat preference
Only
one of the Bornean species is endemic, namely Pencillifera purpurascens
Holloway. The rest are represented on at least one other of the Sunda Shelf
lands and five are also known from the Himalaya or range further.
Two of the more widespread species, Gunda javanica Moore and Ernolatia lida
Moore, are shared with Sulawesi. That island shares an Ocinara with the
Philippines and has single endemic species of Bombyx, Gunda, Ocinara and Trilocha. The fauna of Sulawesi is thus predominantly Oriental, only one species
of the Papuan group, Elachyophtalma inturbida Walker, being represented there.
The majority of Bornean species are found in the lowlands, though Ernolatia
moorei Hutton, Penicillifera purpurascens and Andraca apodecta Swinhoe are
exclusively montane, the Penicillifera only known from tall montane forest that
used to grow on the now ravaged Mesilau Plateau of G. Kinabalu. Two species,
Penicillifera apicalis Walker and Mustilia dierli sp. n. range
from the lowlands to the upper montane zone.
Bibliographic note
Dierl (1978, 1979) did not refer to the rather obscure publication by Lemee
[ 1950] on the Lepidoptera of Vietnam. Three bombycid taxa were described from
N. Vietnam, one a synonym of Gunda javanica as listed under that species. The
other two were Bombyx lemeepauli, a good species in the Bombyx group (but
probably not Bombyx) that has also been taken in N. Thailand, and Ocinara
tamsi,
possibly a synonym of one of the Trilocha or Ocinara species discussed by Dierl
(1978).
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