FNZ 61 - Lucanidae (Insecta: Coleoptera) - Biology
Holloway, BA 2007. Lucanidae (Insecta: Coleoptera). Fauna of New Zealand 61, 254 pages.
( ISSN 0111-5383 (print), ; no. 61. ISBN 978-0-478-09395-7 (print), ). Published 21 Nov 2007
No detailed behavioural or life history studies have been made for any of the stag beetles found in New Zealand. The currently available information comes mainly from label data accompanying the specimens examined and from a few published observations (Hudson 1934; Sherley et al. 1994; Thorpe 2001).
Habitats of adults and larvae
With the exception of Dendroblax earlii, Holloceratognathus helotoides, and a few species of Mitophyllus, adults and larvae of the endemic lucanids are confined to areas of predominantly indigenous vegetation or places where the forests have disappeared but large rotting logs remain on the ground. Adults of D. earlii have most frequently been collected in the vicinity of native forests but a few specimens have been found in pastures and gardens where their larvae are thought to be feeding on roots of grasses. Adults of H. helotoides are usually associated with native trees but on several occasions have been found inside hardwood poles, and the few Mitophyllus species that can extend their range into suburban or rural areas have larvae that are able to develop in rotting branches and logs of some exotic trees. The two Australian species established in New Zealand, Ryssonotus nebulosus and Syndesus cornutus, seem not to invade our native forests, the larvae of R. nebulosus develop in large rotting stumps of several species of introduced trees (Thorpe 2001) and those of Syndesus cornutus also have been found in dead wood of exotic trees as well as in structural timber (Lawrence 1981b). Adults of all of the above species are attracted to lights and may enter buildings at night or become entangled in spider webs on outside walls. Adults of the remaining endemic species are unlikely to be seen near dwellings unless there are stands of native vegetation close by. During the day, they shelter in and under rotten logs, under stones, under loose bark on tree trunks, in leaf litter, among dead leaves trapped in the branches of living trees, and in other similar places. Damp, cool habitats that limit desiccation seem to be preferred by larvae and adults of most of the New Zealand lucanids. Large logs left isolated on open grassy hillsides where previously there was forest may still contain adults and larvae of some species of Paralissotes and Mitophyllus if the logs are in contact with the ground and retain some moisture. The larvae of Geodorcus live in soil that is enriched with humus, sometimes close to the surface if they are under a rotting log, or several centimetres below the surface especially in soil containing guano of burrowing sea birds. Throughout the family it is not unusual for adults and larvae of the same species to be found in close proximity to each other. Adults of Mitophyllus gibbosus and also of M. macrocerus have been observed flying in groups near shrubby vegetation in hot sunshine and those of Holloceratognathus cylindricus and Dendroblax earlii are known to fly at dusk. Information about the flight activity of H. helotoides and most of the other species of Mitophyllus is not available but specimens have occasionally been collected in Malaise traps. The slow moving adults of Geodorcus and Paralissotes are essentially nocturnal but are sometimes active during the day in misty or rainy conditions.
Food of adults and larvae
Adult stag beetles anywhere in the world are rarely seen feeding but it is generally assumed from the structure of the mouthparts that their diet consists mostly of liquids. Exceptions are some Australian lamprimines that eat soft eucalypt and acacia leaves (Britton 1970). The food preferences of adults of Dendroblax earlii, the New Zealand lamprimine, are not known. In the genitalia preparations I have examined of this species and of the other New Zealand lucanids, I have never seen any solid material in the hindgut. Of the many genitalia preparations of exotic lucanids that I have made only two had solids in the hindgut and in both instances the solids had apparently been ingested involuntarily while the beetles were feeding on liquids; the hindgut of a male of Aegus chelifer MacLeay, 1819 from Laos contained conidia of several kinds of fungi, including those of Capnobotrys sp., a sooty mould, which would have been growing on the honey dew presumably ingested by the beetle, and the hindgut of a male of Lissotes menalcas Westwood, 1855 from Tasmania contained chlorococcalean (green algae) cells of Oocystus sp., possibly O. solitaria, a species that is associated with fresh water which the beetle may have been drinking. I am indebted to Dr Gary Samuels for identifying the fungi and Dr Vivienne Cassie for identifying the algae, and I am especially grateful for the associated information they both provided. Geodorcus helmsi adults have been observed feeding on sappy exudations on tree trunks (Holloway 1961; Sherley et al. 1994) and those of G. novaezealandiae held in captivity were seen applying their mouthparts to pieces of apple (Holloway 1961). Some places where Geodorcus and Paralissotes adults have been collected have had no trees or shrubs nearby so it is unclear what, if anything, these specimens were eating. I am unaware of any observations that have been made on adult feeding habits of Holloceratognathus, Mitophyllus, and Paralissotes. There are no records of any of the New Zealand lucanids taking nectar from flowers but some stag beetles in Australia are nectar feeders (Britton 1970).
Rotting wood at or above ground level is the most common food source for lucanid larvae in general but a few species are subterranean, feeding either on roots or on enriched humus. Dendroblax earlii is the only New Zealand stag beetle whose larvae seem to be root feeders. Interestingly, larvae of lamprimines elsewhere in the world develop in rotten wood. Circumstantial evidence suggests that larvae of the unrelated South African lucanine genus Colophon Gray, 1935 are root feeders (Endrödy-Younga 1988), and also that those of the lucanine Sphaenognathus oberon Kriesche, 1922 feed on roots (Bartolozzi & Onore 1993). The gut of the subterranean larvae of Geodorcus contains vast quantities of humus. Undoubtedly the quantity and quality of nutrients in the ingested material will influence the size achieved by the larvae and ultimately that of the adults into which they develop. The very large size of some G. helmsi adults from Bauza Island, Solander Island, and mutton bird islands around Stewart Island is likely to be attributable to the abundant, peaty, guano-enriched soil in which their larvae developed. Larvae of only a few species of Paralissotes are known. Those of P. reticulatus have been found in decayed wood lying on the ground or partly buried especially when the wood is in the soft, red stage of decay (Hudson 1934). Judging from where adults have been collected it seems likely that larvae of some other Paralissotes species, e.g. P. stewarti and P. triregius, ingest firmer dead wood in fallen trunks of trees such as manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides). Holloceratognathus larvae are mostly associated with well decayed wood on the ground or on standing trees, but as noted above, those of H. helotoides may develop in hardwood poles. In New Zealand, larvae of Ryssonotus nebulosus consume rotten wood of privet (Ligustrum lucidum) and Acacia (Thorpe 2001) and probably also of Eucalyptus (Gourlay 1954), and those of Syndesus cornutus have been found in old posts, probably of Eucalyptus and, based only on the presence of adults, probably also in dead Pinus radiata, Macrocarpa, and in milled timber. Larvae of Mitophyllus have mostly been found in damp powdery wood in and under fallen logs of a wide range of native trees and of several exotics. Some of the smaller species of this genus are able to develop in well rotted twigs and thin branches on standing trees and shrubs. Wood decay is classified into brown, white, and soft rot, based on physical and chemical properties, and the decay types do not depend on the species of wood but on the fungi causing the decay (Araya 1993a). Experiments carried out in Japan on the lucanine Prismognathus angularis Waterhouse, 1874 revealed that the dry weights of adults whose larvae developed in brown rotten wood were significantly less than the weights of adults whose larvae fed on white rotten wood (Araya 1993b). It was further found that while P. angularis is a decay type generalist another Japanese lucanid, Ceruchus lignarius Lewis, 1883, is a brown rot specialist (Araya 1993c). No comparable New Zealand information is currently available so it would be useful in future to record decay types very precisely when observing or collecting lucanids in rotten wood.
There is no published information about oviposition, larval and pupal duration, and the life span of adults of any New Zealand stag beetles. Adults of most of the species have been collected all year round. Some Mitophyllus adults can be found deep inside rotten logs throughout the year and when handled they are very inactive, suggesting that they may be in some sort of hibernation state. It is also possible that, until the food supply is exhausted or the substrate becomes unsuitable several consecutive generations may be produced without the adults ever leaving the original larval site. Remains of dead adults are often present in rotten wood that contains larvae. For several years wood samples containing Mitophyllus larvae were maintained in the laboratory of the New Zealand Arthropod Collection and it was found from these that larvae of various sizes were present at all times of the year and that adult emergence also occurred throughout the year. In some Geodorcus adults the fore tibial teeth have become blunt tipped which may indicate that the specimens have lived for a long time but equally it could be that the teeth are worn down because the beetles have been burrowing through very hard soil. Copulation has been observed taking place in Geodorcus novaezealandiae in mid October (Holloway 1961), in G. alsobius in January (Sherley et al. 1994), in Paralissotes reticulatus in November (Holloway 1961), and in P. rufipes in January (present volume).