FNZ 3 - Anthribidae (Insecta: Coleoptera) - Biology
Holloway, BA 1982. Anthribidae (Insecta: Coleoptera). Fauna of New Zealand 3, 272 pages.
(
ISSN 0111-5383 (print),
;
no.
03.
ISBN 0-477-06703-4 (print),
).
Published 23 Dec 1982
ZooBank: http://zoobank.org/References/AC1DC576-5021-40DE-9BD7-0F7C591C6521
Biology
Habitats of adults and larvae
All New Zealand's Anthribidae are phytophagous, and most species occur only in natural plant communities. The plant habitats do not have to be extensive areas of original forest - a small patch of mainly second-growth vegetation or a few clumps of Muehlenbeckia and New Zealand flax in an unmodified coastal setting can support anthribids. Species that may be abundant in pockets of bush on the outskirts of suburban housing developments are rarely attracted to their known host plants growing in adjacent gardens and parks. The one exception is Sharpius brouni, which is common through much of New Zealand. Larvae of a few endemic species are able to develop in exotic plants, particularly when these are intermingled with native trees and shrubs.
Most species are associated with standing vegetation, and have larvae that are endophytic in dead and dying branches of trees and shrubs. The adults feed mainly on fungal material growing on the bark of weakened woody plants. Adults of a few species with arboreal larvae have been extracted from leaf litter as well as being beaten from vegetation. Whether these adults were actually feeding on saprophytic fungi of the forest floor or had recently emerged from fallen twigs is not known. Adults of Notochoragus chathamensis, Xenanthribus hirsutus, and a few species of Dysnocryptus have only ever been found in leaf litter (or, very rarely, under wrack). Their larvae are unknown, but will perhaps be found to develop inside rotting twigs and branches lying on the forest floor. Adults of Caliobius littoralis occur in litter associated with ground-nesting seabirds, and the larvae will doubtless be found in the same habitat.
A few species of Dysnocryptus are associated with monocotyledons growing in swamps or close to the sea, where they may be submerged from time to time, but in general anthribids do not live in places that are frequently exposed to water. The two exceptions are Lichenobius littoralis, which has larvae that live inside rock-encrusting lichens of the spray zone and adults that move freely over the surface of this lichen; and Z. maritimus, adults of which have been collected from encrusting plant material on wave-washed rocks of the Bounty Islands. The habitat preferences of adults and larvae are summarised in Appendix 3.
Host plants of larvae
Label data of reared specimens indicate host plants of the larvae of 39 species. For a further six species larval host-plant relationships can be assumed from the occurrence of adults on various plant species; males and females are often abundant on weakened and cut branches of the food plants of their larvae.
Altogether 2 species of lichens, a genus of ascomycete fungi, a genus of basidiomycete fungi, a genus of ferns, 7 genera (representing 4 families) of gymnosperms, 15 genera (representing 7 families) of monocotyledons, and 55 genera (representing 35 families) of dicotyledons are known to serve as host plants for anthribid larvae in New Zealand.
The actual relationship between the larvae and their host plants has not been studied in detail, but it seems likely that nutriment is obtained not directly from the plant tissue itself but from fungi, such as Xylariaceae, that have invaded the host plant. The larval food could consist either of fungal material alone or of host-plant tissue that has been altered by the presence of parasitic fungi. Penman (1978) has suggested that third-instar larvae of Euciodes suturalis may be feeding on fungi that commonly infest the interior of the dried seed-head stems of cocksfoot where they live, although first and second instars are present in developing seed-head stems, presumably without this fungal growth. In an Arecopais spectabilis larva that I examined the hindgut contained numerous ascospores and fragments of fungal fructifications in addition to tissue of the dead nikau palm frond in which the larva was found.
Lichenobius is the only New Zealand genus with lichenivorous larvae, and it is doubtful whether these larvae could deve1op in any other plants.
The endemic choragine Notochoragus crassus and two endemic anthribines, Lophus rudis and Pleosporius bullatus, have been reared from ascomycete fruiting bodies growing on beech and tawa, but they have also been reared from dicotyledons showing no obvious fungal growths. The only basidiomycete fungus with which larval anthribids in New Zealand are known to be associated is a rust that induces galls on acacias. It is Australian in origin, and the choragine Araecerus palmaris that develops inside the galls is an Australian species established here. A. palmaris can also develop inside mummified fruits of various dicotyledons.
Tree ferns may be among the larval host plants of Dysnocryptus rugosus, as relatively large numbers of adults have been beaten from their fronds, but larvae are known to develop in old stems of Gahnia, a monocotyledon.
Nine endemic anthribines have been reared from gymnosperms. Larvae of Cacephatus incertus and C. inornatus apparently are confined to gymnosperms, but do not discriminate between endemic and exotic species. Androporus discedens, Helmoreus sharpi, Phymatus cucullatus, P. phymatodes, and Sharpius brouni have also been reared from dicotyledons; Cacephatus aucklandicus and Phymatus hetaera have been reared from gymnosperms as well as monocotyledons and dicotyledons.
Monocotyledons seem to be the only group of plants selected as hosts by larvae of three anthribine species. Arecopais spectabilis, an endemic species, has been reared only from nikau palm fronds; Isanthribus phormii, also endemic, is probably confined to New Zealand flax; and the adventive grass stem anthribid Euciodes suturalis has been reared only from seed-head stems of introduced grasses. Of the endemic choragines, Dysnocryptus and Micranthribus probably develop in native Cyperaceae and in both New Zealand and South American species of Cortaderia (Poaceae) as well as being associated with plants of several dicotyledonous families.
Not surprisingly, dicotyledons provide host species for a large number of larval anthribids. Seventeen endemic species have been reared from dicotyledons, and at least some of these have larvae that seem to be confined to a single plant family or genus. For example, Hoherius meinertzhageni has been reared only from endemic Malvaceae, Lophus lewisi from Nothofagus (Fagaceae), and Liromus pardalis from Coprosma (Rubiaceae). However, most of the New Zealand anthribids whose larvae are associated with dicotyledons have been reared from several genera distributed among unrelated families.
The greatest number of larval host-plant records is for Sharpius brouni, which has been reared from plants belonging to 14 genera of dicotyledons, representing 11 families, and from 2 genera of gymnosperms belonging to different families.
Very little information is available about the sites selected by larvae within the host plants. Larvae of Cacephatus incertus, C. inornatus, and C. vates are often found deep in the sapwood, and C. huttoni larvae feed in the pithy rays of dead stems. Sharpius brouni has been reared from dead, but intact, twigs as well as from rotten stumps of trees. In twigs its larvae feed in the subcortical zone. The larvae of HeImoreus sharpi and Hoherius meinertzhageni feed subcortically and in the bark of dying twigs and branches, and larvae of Dasyanthribus purpureus have been found under bark flakes of living trees. Lichenobius littoralis larvae form feeding tunnels just below the surface of rock-encrusting lichens, whereas L. silvicola larvae apparently extend their workings down into the bark on which their host lichen is growing.
Host plants of endemic and adventive Anthribidae of New Zealand are listed in Appendix 4.
Food of adults
The diet of adult anthribids can be determined by examination of hindgut contents, obtained by macerating the abdomen.
The plant material most commonly found in New Zealand species was fragments of fungi, mainly ascomycetes and Fungi Imperfecti. Spores and hyphae of rusts (Basidiomycetes) were identified from Araecerus palmaris, Euciodes suturalis, and Cacephatus propinquus. Lichen tissue was present in Lichenobius littoralis, L. silvicola, and Cacephatus aucklandicus. Fragments of bark and epidermal tissue, presumably from part of the fungal substrate, were present in some preparations. No pollen grains were found.
The fungal material consisted of spores, apparently unaltered externally during digestion, and fragments of hyphae and ruptured fruiting bodies. Some of the preparations contained hundreds - even thousands - of spores, often of a single species, hut in others there were only small numbers of spores, frequently representing several species. The hindgut of some specimens contained only fragments of fungal fruiting bodies and hyphae. Few prenarations contained no fungal material at all.
The beetles probably derive most of their nutriment from vegetative hyphae and from mucilaginous material inside the fungal fructifications. From the amount of vegetative fungal material present in most preparations it is evident that whole fruiting bodies are eaten, often with some of the supporting fungal tissue (stroma). The extent to which spore contents may be digested is not known. Many spores have thick walls that are continuous except for localised thinning at the sites of germination pores and slits. Some of the conidia (asexual spores of Fungi Imperfecti) had their end cells digested away.
The most common ascomycete spores identified in the preparations belonged to Xylariaceae, but ascospores of Sordariaceae were present in the two species of Hoplorhaphus. Hyphae and ascospores of Euantennariaceae (true sooty moulds) were identified in the gut of Cacephatus inornatus, Dasyanthribus purpureus, Garyus altus, and Pleosporius bullatus; the last-named also contained ascospores of Pleosporaceae. These moulds grow on the honey dew deposited by some scale insects (Coccoidea). Knowing of the association of some adult anthribids with true sooty moulds, it is now not difficult to see how larvae of a few Northern Hemisphere species could have become predators of the sessile scale insects that produce honey dew (and their eggs). Pirozynski & Weresub (1979) consider the Euantennariaceae to be a relict group of fungi, the present-day distribution of which results from overland migrations of biotas in the early Cretaceous, more than 80 million years ago. If, as seems likely, some adult anthribids are very slow to change their feeding habits, then anthribid/euantennariacean associations could be extremely ancient.
All the basiodiomycetes identified in the hindgut preparations were rusts (Uredinales). Rust spores ingested by adults of Araecerus palmaris belonged to the same species that induces the acacia galls in which their larvae develop. Those found in the gut of the grass stem anthribid Euciodes suturalis belonged to Puccinia, a genus commonly found on grasses and weeds.
It was expected that the gut contents of the two specimens of Lichenohius maritimus collected on encrusting plant material in a wave-washed crevice on the Bounty Islands would include fragments of algae or lichens, but only fungal spores and hyphae - apparently not associated with lichens - were present, so presumably these beetles had been feeding on a marine fungus.