The Norfolk Island puzzle: Identifying new insect and spider species

The ongoing identification of insect and spider specimens collected during the Australian Museum-led Norfolk Island expedition is throwing up a host of new family and species records and plenty of puzzles. The AM Arachnology and Entomology team tell us about these exciting finds and the work ahead.

The insects and spiders of Norfolk Island and Phillip Island are incompletely known so we need to improve our knowledge of what species are present to inform conservation measures. During Phase 1 of the Australian Museum-led Norfolk Island expedition, we collected a wide variety of spiders and targeted certain groups of insects, specifically plant-feeding beetles. The techniques used were hand searching (e.g., looking beneath woody debris, night collecting), sifting litter over a tray, knocking animals off vegetation into a tray (a technique called ‘beating’) and setting overnight traps on the ground.

One problem with faunal surveys for invertebrates is that identifying specimens takes a long time and there are many difficulties in such identifications. Some species may be quite easy to identify – they may be part of a group that has been thoroughly revised in the region so we have keys and illustrations, or they may already be known to occur on Norfolk Island (and/or on nearby Phillip Island). But many insect and spider groups are less well known, and for a place out in the ocean where colonization might have come from any direction, that is quite a problem.

The Norfolk Island region has faunal and floral biogeographic links with Australia, New Zealand and New Caledonia, not to mention the potential for human introductions over many years of settlement. As a result, it is often not possible for us to be sure of the status of a species we find – is it a unique endemic species that occurs nowhere else in the world, or is it a poorly known or unidentified species that is actually quite widespread? If the latter, then is it native to the island, or have people brought it here?

Our AM beetle expert, Dr Chris Reid, has now examined the Coleoptera and reports 69 species, including 7 longhorn beetles (Cerambycidae), 7 leaf beetles (Chrysomelidae) and 29 weevils (Curculionidae) – these were the plant feeding target groups and several of these species are undescribed. The most interesting beetle capture is a new flightless species of Phanodesta (Trogossittidae) – a genus previously only known from New Zealand, Lord Howe Island and the Juan Fernandez Is (Chile). For insects in general, however, most of the specimens are still being identified but we do know that there is a new species of crane fly.

Among the spiders, we have almost 60 species separated and identified as far as possible. Some exciting finds include spiders from nine families that have never been recorded in the Norfolk Island region before 2022. Images of four of these were posted to iNaturalist prior to our visit but another five are completely new records. The conservation status for most of the nine is unclear; so far three have been identified as known (non-endemic) species, one falls into the ‘puzzle’ category, and one cannot be identified further without more specimens. The other four are in groups that have not been worked on in the region.

In both insects and spiders, we keep encountering puzzles – specimens that look very similar to one or more named species, but not quite. Are the differences significant? Our Odonata expert and AM Research Associate, Gunther Theischinger, is working on the identification of a damselfly species that doesn’t seem to have any previous records on Norfolk Island but does not quite match species in Australia. One of the spider puzzles is a species of net-casting spider, Menneus sp. These spiders are relatively large, so you might think they would have been noticed years ago, but the first records are from iNaturalist, such as in the photograph above from early 2022. We collected two specimens in November 2022, and those seem to be intermediate between two species known from Australia. What does this mean? Further work will be needed to solve this puzzle.

On the other hand, some of the species we found are well-known and have almost certainly been introduced quite recently. Some of these are already widespread and common on Norfolk Island itself (but mostly not on Phillip Island), both around people and in the National Park and reserves. Island ecosystems are constantly evolving and the addition of new species, which are often effective colonisers, can be a disaster for locally evolved endemic species. The new arrivals may be adaptable and/or aggressive, they may take over suitable habitat, or even directly feed on the native species. To enable effective conservation, it is vital that we take stock of the current situation - and this means trying to identify all our specimens as far as possible.

We will carry on with our identifications and make our findings publicly available. In some groups we hope to describe new species in collaboration with specialists in those groups – maybe we will need to collect more specimens to resolve some of the puzzles and decide that the species is new. But many specimens will only get fully identified in years to come by being included in more widescale projects that look at a whole group of species and where they are found. This is where museum collections are particularly valuable because they make specimens available to researchers. The diversity of insects and spiders is so immense that invertebrate taxonomists by necessity need to specialise on certain groups. Such specialists work not only in our Australian museums but in similar institutions and universities around the world. After we have identified our specimens to a group and entered the data into our collection management system, external researchers can access the specimen data online. They can then request a loan of the specimens or high resolution images if those are suitable for identifying the group.