Observations on the biology and host plants of the ... - Calodema

Calodema Volume 1 (2003)
<strong>Observations</strong> on the biology and host plants of the Australian flea beetle,
Halticorcus platycerii Lea, 1917 (Coleoptera: Chrysomelidae: Alticinae)
by Dr Trevor J. Hawkeswood*
*270 Terrace Road, North Richmond, New South Wales, 2754, Australia.
Hawkeswood, T.J. (2003). <strong>Observations</strong> on the biology and host plants of the Australian flea beetle,
Halticorcus platycerii Lea, 1917 (Coleoptera: Chrysomelidae: Alticinae). Calodema, 1: 31-34.
Abstract. The larva and adults of the Australian flea beetle, Halticorcus platycerii Lea, 1917 (Coleoptera:
Chrysomelidae: Alticinae) have been collected from north-eastern New South Wales during 1993-1995 and
those biological observations undertaken on them are provided here for the first time. The known larval host
plants of the larvae are Platycerium bifurcatum Jonch. & Hennip. (Polypodiaceae) and Asplenium australasicum
(J.Sm.) Hook. (Aspleniaceae), while adults are presently only known to feed on the former mentioned host
plant. Halticorcus platycerii is the only chrysomelid beetle from Australia known to be restricted to ferns
(Filicopsida, Pteridophyta). There is one museum record indicating Orchidaceae as host, but this has not been
substantiated and probably represents a stray resting record.
Introduction
The genus Halticorcus Lea, 1917 (Coleoptera: Chrysomelidae: Alticinae) presently contains
two species of highly convex and semicircular, blackish, shiny beetles occurring in Papua New
Guinea and Australia (Samuelson, 1969). The only known Australian species, Halticorcus
platycerii Lea, 1917, measures 3.2-3.5 mm in total body length, and is shiny bluish-black or
dark greenish-black in colour with basal and central orange-red spots on the elytra (Lea, 1917;
Froggatt, 1917; Samuelson, 1969). The host plant of this beetle has been recorded as the
Common Staghorn Fern, Platycerium bifurcatum Jonch. & Hennip. (Lea, 1917; Froggatt,
1917; Samuelson, 1969, Hawkeswood & Furth, 1994). The larva has been illustrated by
Froggatt (1917) and McKeown (1942, 1944) but has never been described in any detail. In
fact, the larvae of Australian Alticinae are almost totally unknown and none have been
described scientifically, as far as I am aware. Some biological aspects of the larvae and adults
are reviewed here and some new data provided. A discussion on chrysomelids associated with
ferns (Filicopsida: Pteridophyta) is also provided.
Materials and Methods
Larvae of several stages (but mostly mature) were collected from the infested fronds of the host plants during
1993-1995 from the Hastings Point area, north-eastern New South Wales, Australia (28°20’S, 153°35’E).
<strong>Observations</strong> on adults were undertaken intermittently by the author during 1993-1995. Numerous Platycerium
ferns and other species which were growing in residential gardens were examined for the presence of H.
platycerii and observations recorded. Infested plant material was also collected and later carefully dissected in
the laboratory by the author.
<strong>Observations</strong>
There appears to be at least two generations of H. platycerii per year, with adults appearing on the leaves of
their host plants during April-June (autumn to early winter) and during September to November (spring to early
summer). A few early or late emerging adults may be found on the foliage outside these main periods of adult
activity but most adults are present during the above-mentioned periods. Eggs are apparently laid in the
mesophyll tissue at the ends of the fronds (where the fronds are bifurcate) of the host plant Platycerium
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bifurcatum Jonch. & Hennip. (Polypodiaceae) and are usually located near recent feeding holes caused by the
adults (see description of these below).
The young larvae hatch and mine the fronds towards the centre of the plant following the veins along the
longitudinal axis of the frond. In some cases, the larvae may turn and mine in the opposite direction towards
the tips of the fronds or may make another mine adjacent and parallel to a previous one. Often the mines of two
or more larvae will coalesce and this group of two or more larvae will share a common and more extensively
mined area along the frond for a distance of 50% or more from the apex. The epidermis of both sides of the leaf
soon dies and becomes brown, wrinkled and dried once the palisade and spongy mesophyll tissues have been
completely devoured by the developing larvae. Larval frass collects extensively in the mined areas. The larvae
are yellow in the early stages while the mature larvae, 6-7 mm in total length, are bright orange to almost red in
colour. These bright larvae can often be observed through the cuticle and epidermis of the infested fronds but
usually are camouflaged by the dead, brown frond material and the dark coloured faeces which surrounds the
larvae in the mined areas. Pupation apparently occurs at one end of the mine and adults emerge through a slit in
the abaxial (lower) epidermis.
The adults occur mostly on the adaxial (upper) epidermis of the fronds where they chew characteristic ovalshaped
(sometimes circular) incisions through the adaxial epidermis and cuticle, through the palisade and
spongy mesophyll to the lower epidermis which is not usually chewed. The density of the chewing holes varies
from 4-12 per square centimetre and these holes are situated mostly at the ends of the fronds. These feeding
holes measure mostly 1.8-2.5 mm in diameter (range 1.5-3.0 cm). Adults also mate on the upper surface of the
fronds but flick away with great rapidity upon any slight disturbance or approach. The adults are very
conspicuous when resting on the fronds as the black and red coloration on the elytra contrasts with the deep
green colour of the fronds. Predation by other insects upon adults has not been observed. No other leaf mining
or external leaf feeding insects were observed on the hosts occupied by H. platycerii.
Other field data obtained on fronds, leaf mines and larvae are presented in Table 1.
___________________________________________________________________________
Table 1. Size of fronds of Platycerium superbum Jonch. & Hennip. (Polypodiaceae), number of associated
larval mines per frond of Halticorcus platycerii Lea and colour of larvae, from Hastings Point, New South
Wales, 15 June 1993
___________________________________________________________________________
Frond length Width of frond at No of mines No. of larvae Colour of larvae
(cm) widest point (cm) per frond
___________________________________________________________________________
45.5 6.8 2 1 Orange
38.0 2.1 2 1 Red
41.5 7.5 4 0 -
66.0 6.4 2 0 -
21.0 2.2 1 1 Orange
20.5 3.0 1 0 -
46.5 3.3 3 0 -
31.5 2.7 2 1 Red
31.5 6.8 2 1 Dark orange
50.0 4.8 1 1 Dark orange
37.0 5.4 2 0 -
53.0 3.0 2 0 -
___________________________________________________________________________
Mean 41.0 4.5 2.0 0.5 -
SD 12.9 1.9 0.8 0.5 -
Range 20.5-66.0 2.1-7.5 1-4 0-1 -
___________________________________________________________________________
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Discussion
As far as I am aware, Halticorcus platycerii Lea is the only species of Australian
Chrysomelidae known to feed on the foliage of ferns (Filicopsida). The only known host
plants of the beetle are Platycerium bifurcatum Jonch. & Hennip. (Polypodiaceae) and
Asplenium australasicum (Sm.) Hook. (Aspleniaceae)(Hawkeswood & Furth, 1994). There is
one museum record indicating Orchidaceae as host, but this has not been substantiated and
probably represents a stray resting record (Hawkeswood & Furth, 1994). Mostly H.
platycerii adults are found on ferns in residential gardens and supposedly they are very
difficult to detect or collect when the ferns are growing 50 metres or more above ground level
in their native habitats in the subtropical rainforests of south-eastern Queensland and northeastern
New South Wales. The fact that this distinctive species was not discovered and
named until 1917 attests to this situation, because ferns growing in tall trees are difficult to
sample for invertebrates, unless they fall to the ground during storms etc. and retain the
beetles which can be later collected. Froggatt’s material came from sites similar to where my
own observations were undertaken, viz. residential gardens.
The association of chrysomelids with ferns has been reviewed relatively recently by Jolivet &
Hawkeswood (1995). Hendrix (1980) earlier recorded only 5 genera and six species of
Chrysomelidae feeding on ferns. There are many others but most of the fern-feeders belong to
the subfamily Alticinae, e.g. Alema on tree ferns (Cyathea, Cyatheaceae) in New Zealand,
(Jolivet & Hawkeswood, 1995), Schenklingia with two species on Nephrolepis
(Oleandraceae) in Malaysia and Micronesia (Bryant, 1948; Samuelson, 1969, 1973; Jolivet &
Hawkeswood, 1995), Setsaltica on Cyathea at high altitudes in New Guinea (Samuelson,
1969, 1970), Manobia on Cyathea atrox and other ferns in New Guinea (Samuelson, 1969,
1970; Jolivet & Hawkeswood, 1995) etc. Recently, Kimoto (1984) and Kato (1991) recorded
Manobia lewisi Jacoby feeding on Cyclosorus acuminatus (Aspidiaceae), Minota nigropicea
(Baly) on Pteridium aquilinum, Dryopteris erythrosora and Cyrtomium fortunei)(all
Aspidiaceae), Schlenkingia hiranoi Takizawa on Lemmaphyllum microphyllum and
Loxogramma salicifolia (Polypodiaceae) etc. (see also Jolivet & Hawkeswood, 1995). Other
alticine chrysomelids are known from Pteridium aquilinum (= P. esculentum)
(Dennstaedtiaceae) in Papua New Guinea (Kirk, 1976) although none have been recorded on
this plant in Australia (Jolivet & Hawkeswood, 1995).
It should be noted that most of these fern species are from genera with large, broad, rather
thick, fronds (see e.g. Table 1, this paper) which are able to support the burrowings of the
larvae and the thicknesses of their bodies. The parenchyma tissues in their leaves are
composed of large cells with high concentrations of carbohydrates and minerals. Some of
these fern records are of species which are not epiphytic, e.g. Cyathea, Pteridium. Hence
there is quite a diversity of fern species inhabited by a diversity of Alticinae. However,
considering the number of fern species in the world and the number of Alticinae (many of
which are still to be discovered), the actual number of species of Chrysomelidae known from
ferns is rather small. This may be because the niches in which ferns live, e.g. cracks in rock
overhangs and branches of trees, in moist, shady habitats along creeks etc. are actually hostile
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environments to thermophilic leaf beetles, in terms of their microclimate, and relative dark
seclusion. Thus only a few leaf beetle species have adapted by leaf mining the fronds. Further
studies of the relationships of H. platycerii and other chrysomelids with ferns should reveal
interesting co-evolutionary adaptations not yet realised.
References
Bryant, G.E. (1948). A new species of Eucylca (Halticinae, Coleoptera) from Malaya feeding
on Nephrolepis biserrata. Annals and Magazine of Natural History (series 11), 14:
587-588.
Froggatt, W.W. (1917). Entomological notes. Agricultural Gazette of New South Wales, 28:
891-895.
Hawkeswood, T.J. & Furth, D.G. (1994). New host plant records for some Australian
Alticinae (Coleoptera: Chrysomelidae). Spixiana, 17: 43-49.
Hendrix, S.D. (1980). An evolutionary and ecological perspective of the insect fauna of ferns.
American Naturalist, 115: 171-196.
Jolivet, P.H. & Hawkeswood, T.J. (1995). Host plants of Chrysomelidae of the World- An
essay about the relationships between Leaf-beetles and their food plants. Backhuys
Publishers, Leiden, The Netherlands: 1-281.
Kato, M. (1991). Leaf-mining chrysomelids reared from Pteridophytes. Japanese Journal of
Entomology, 59: 671-674.
Kimoto, S. (1984). Chrysomelidae. In: The Coleoptera of Japan in Colour. Hayashi, M.,
Morimoto, K. & Kimoto, S. (Eds). 4: 147-224. Hoikusha Publishing Company,
Osaka.
Kirk, A.A. (1977). The insect fauna of the weed Pteridium aquilinum (L.) Kuhn
(Polypodiaceae) in Papua New Guinea: a potential source of biological control agents.
Journal of the Australian Entomological Society, 16: 403-409.
Lea, A.M. (1917). Notes on some miscellaneous Coleoptera with descriptions of new
species. Part III. Transactions of the Royal Society of South Australia, 61: 121-322.
McKeown, K.C. (1942, 1944). Australian Insects. Royal Zoological Society of New South
Wales, Sydney.
Samuelson, G.A. (1969). Alticinae of New Guinea, III. Schlenkingia and allies (Coleoptera:
Chrysomelidae). Pacific Insects, 11: 33-47.
Samuelson, G.A. (1970). Alticinae of New Guinea IV. (Coleoptera: Chrysomelidae). Pacific
Insects, 13: 513-518.
Samuelson, G.A. (1973). Alticinae of Oceania (Coleoptera: Chrysomelidae). Pacific Insects
Monographs, 30: 1-165.
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