Corinne Watts

History of weta (Orthoptera: Anostostomatidae) translocation in New Zealand: lessons learned, islands as sanctuaries and the future

Establishing new populations by transferring founder individuals from source populations has been effective for managing the recovery of many threatened species including some weta (Orthoptera: Anostostomatidae) in New Zealand. These large-bodied flightless insects are ‘flagship species’ for insect conservation in New Zealand and many are rare or threatened. The declining abundance of most weta species, particularly giant weta, can be attributed to the introduction of mammalian predators, habitat destruction, and habitat modification by introduced mammalian browsers. New populations of some weta have been established in locations, particularly on islands, where these threats have been eliminated or severely reduced in order to reduce the risk of extinction. Some populations were established to provide food for endemic vertebrates, ecosystem restoration and ready access for the general public. We illustrate how methods for both transferring weta and monitoring them have become more sophisticated by using a series of case studies. Other transfers of weta not included in the case studies are also summarised. We conclude by re-iterating the importance of documenting the transfer and post-release monitoring for all insect transfers, both for biogeographical reasons and to provide information to improve future transfers.

The importance of urban reserves for conserving beetle communities: a case study from New Zealand

Urban reserves provide a major opportunity for conservation of indigenous biodiversity in the heavily urbanised landscape of Waitakere City (Auckland), New Zealand. However, there is little documented information on what indigenous fauna survives in these reserves. Beetle (Coleoptera) communities associated with two small, isolated urban reserves and two sites in a larger forest area within the Waitakere Ranges were sampled using pitfall traps and analysed. A total of 887 beetles, from 23 families and 89 recognisable taxonomic units were caught. The urban reserves had a marked reduction in species richness and abundance of beetles compared with the sites within the larger forest areas. Various environmental factors influencing the distribution of beetles across the sites were investigated. The most important factors were size of fragment, local forest cover and soil moisture. ‘Common’ species (>5 specimens in the total dataset) found in the Waitakere Ranges and small urban reserves, were either endemic or indigenous to New Zealand. Therefore, even though these reserves may be isolated from a larger, more continuous forest tract, they have considerable potential as reservoirs of beetle diversity in highly modified landscapes and the contribution of urban reserves to the local sustainability of beetle assemblages emphasises the importance of maintaining ‘green’ areas in and around cities.

The interactive effects of livestock exclusion and mammalian pest control on the restoration of invertebrate communities in small forest remnants

Abstract In many agricultural landscapes, significant biodiversity gains can be made by improving the ecological condition of degraded remnants of semi‐natural habitat. Recent emphasis has been on the level of management intervention required to initiate vegetation recovery in small forest remnants, but no comparable emphasis has been placed on benefits for invertebrate communities. In the Waikato region, New Zealand, we tested the effects of livestock exclusion, mammalian pest control, and their interaction, on leaf‐litter invertebrate communities in 30 forest remnants, using a space‐for‐time substitution approach. A total of 87 376 invertebrates were extracted from 964 leaf‐litter samples. Invertebrate density was an order of magnitude lower in remnants than in nearby large forest reserves. For key taxa, such as Diplopoda, Isopoda, Coleoptera and Mollusca, 10‐ to 100‐fold lower densities were recorded in remnants with no pest control, particularly where livestock were not excluded. By contrast, other taxa such as Thysanoptera and For‐micidae (Hymenoptera) had up to 100‐fold greater densities in remnants with recent stock exclusion and pest control. These changes led to a significant livestock exclusion x pest control interaction effect on the degree of invertebrate community dissimilarity between forest remnants and forest reserves. Using structural equation modelling, we found that treatment effects were largely mediated by a cascading series of indirect causal paths involving altered soil chemistry, vegetation composition, and litter mass relative to large forest reserves, although the livestock exclusion × pest control interaction was inadvertently confounded with differing slopes and areas of remnants in different treatments. Livestock exclusion and mammalian pest control have significant, but contrasting, effects on invertebrates in the first 10–20 years following livestock exclusion from forest remnants, with mammalian pest control having limited benefit for the leaf‐litter invertebrate fauna without livestock exclusion.

Critical issues facing New Zealand entomology

Here, we identify current high-priority issues in New Zealand entomology. These ‘critical issues’ were defined by being of national entomological interest, and in urgent need of research or attention. The issues were derived in consultation with the Entomological Society of New Zealand members and as part of a workshop at the 62nd New Zealand Entomological Society Conference. We present a list of nine priority areas (presented here without any ranking priority). These areas are: 1. conserving indigenous invertebrate diversity; 2. limiting predator pressure exerted by exotic vertebrate predators; 3. limiting the effects of invasive invertebrates, especially Vespula wasps in honeydew beech forests; understanding the influence of pesticides and pathogens on honey bees; 4. maintaining and enhancing efficient biosecurity systems to keep out invasive pests and diseases; 5. enhancing support for taxonomy; 6. enhancing entomological teaching, training and support for entomology graduates; 7. utilising the hidden knowledge of retired entomologists; and 8. supporting amateurs in entomology. For each of these topics we briefly discuss the state of the current situation or knowledge gaps. We consider this a road map to enhance entomology in New Zealand.

Beetle community changes following pest mammal control at two biodiversity sanctuaries in Wellington, New Zealand

Introduced pest mammals impact widely on New Zealand invertebrates, but community-level responses to mammal removal are largely unmeasured. Beetles were pitfall-trapped for 7–10 years to examine how their communities responded to near eradication of all mammals except mice (Mus musculus) within a fenced sanctuary (Zealandia), and to sustained mammal control at an unfenced sanctuary (Otari-Wiltons Bush). In Zealandia, beetle abundance unexpectedly declined for 6 years after mammal eradication before stabilising. Beetle community composition changed, perhaps due to increased predation by birds and mice, but species richness, size distribution and trophic composition did not. At Otari-Wiltons Bush, beetle abundance also declined, in the presence of few but diverse mammals. Identifying causes of invertebrate community changes will be improved with study replication, more ‘before’ data, and targeted measurement of possible explanatory factors. Five recommendations are made for future insect community monitoring, including reconstructing fossil invertebrate communities to sharpen restoration objectives.

Insect Conservation in New Zealand: An Historical Perspective

The exciting prospect of discovering New Zealand’s untapped insect fauna was incentive enough for the early collectors of natural history specimens. Investigation of the fauna began with Joseph Banks on the Endeavour in 1769 and was continued by a devoted group of eighteenth century naturalists who occasionally voiced their concern at the rate of destruction and modification of the indigenous ecosystems as European Imperialism fuelled the development of agriculture for the economic base of the new colony. Although records are sparse, at least two early entomologists expressed their opinions in the early twentieth century. G.V. Hudson aired his concern about the dwindling numbers of native insects in a Presidential Address to the Wellington Philosophical Society (Hudson 1900) and later recollected that: ‘every summer throughout the “eighties” great fires raged on the hills around Wellington and the air was thick with smoke for days together’. The concept of preserving native fauna was then in the minds of very few and those who protested at the reckless destruction of the forest were regarded as “cranks” …’ (Hudson 1950, pp. 161–162). Back ‘home’ in Britain, another entomologist, Commander James J. Walker (1921) in his presidential address to the Entomological Society of London, also drew attention to the potential plight of New Zealand’s insect fauna when, after discussing the rich and endemic attributes of the flora that were being lost both to agriculture and weed invasion, he said that ‘the disastrous effect on all forms of life of this destruction and replacement … (necessitate) immediate and thorough research in what still remains of the endemic animal life of New Zealand, before many of its most interesting forms are lost forever.’ However, nothing was done and no consideration was given to the need to conserve invertebrates. Instead, it was the ornithologists who paved the way for the first conservation ethic as they focussed on New Zealand’s unusual and dominant bird life. This began with the influential politician, Thomas Potts, who raised awareness for conservation in the 1850s and was eventually in part responsible for the declaration of island reserves for Resolution, Secretary, Little Barrier, and Kapiti islands, gazetted between 1891 and 1897 (Young 2004). Conservation action on behalf of invertebrates did not occur despite increasing knowledge of their uniqueness and significance in understanding southern biogeography issues (Gibbs 2006).

Beetle community responses to grey willow (Salix cinerea) invasion within three New Zealand wetlands

Abstract We investigated the effects of invasion by introduced grey willow (Salix cinerea) on beetle communities within four wetland vegetation types: native vegetation, native vegetation following grey willow removal, native vegetation undergoing grey willow invasion and dense grey willow-dominated vegetation. In total, 1505 beetles from 90 species were collected using modified Malaise traps. Native wetland vegetation had significantly lower beetle species richness than willow-dominated vegetation and was dominated by herbivores, whereas detritivores characterised willow-dominated vegetation. Beetle abundance was highest in the willow-dominated vegetation and mostly comprised detritivores. In contrast, beetle abundance was lowest in native wetland vegetation, but had even proportions of herbivores and detritivores. Native wetland vegetation had a high proportion of native beetles present. As grey willows invaded, introduced beetles became more common. The beetle community composition differed significantly between grey willow-dominated vegetation and native wetland vegetation. These compositional differences were mainly due to the increasing complexity of vegetation structure following grey willow invasion. The beetle communities within restored native wetland vegetation were most similar to those within the native wetland vegetation. From a conservation perspective, these results are encouraging and suggest that, although grey willows dramatically alter the composition of beetle communities present, these communities can be restored to a beetle fauna that is similar to those found within native wetland through the removal of the willows.

Habitat use, Behavior and Movement Patterns of a Threatened New Zealand Giant Weta, Deinacrida heteracantha (Anostostomatidae: Orthoptera)

Abstract Wetapunga (Deinacrida heteracantha), New Zealands largest insect, were formerly abundant in forests of northern New Zealand. However, they are now restricted to onepopulation on mammal-free Little Barrier Island (3083 ha). This study investigated the movements, habitat use and behavior of 22 adult wetapunga fitted with miniature radiotransmitters for up to 18 nights. Adult wetapunga appeared to be quite mobile, with males (16 m per night) moving further than females (8 m per night). Differences in the distances travelled by adult male and female wetapunga between daytime refuges appear due to differences in reproductive behavior. Wetapunga were associated with silverfern, nikau palm, kanuka, and kohekohe within second-growth coastal forest on Little Barrier Island. The majority of wetapunga were found above ground level, but were also occasionally found moving on the ground. In addition, adult wetapunga were found in relatively open sites with little or no cover and were clearly visible by day. Wetapunga were generally solitary and the majority of their activities, such as feeding, movements and oviposition, occurred at night. The one exception is mating (actual copulation and pre-, post-copulatory behavior), which usually occurred during daylight after weta had paired during the previous night. During the study, one male wetapunga was eaten by an unknown avian predator. Radiotelemetry has extended our knowledge of adult wetapunga behavior and this monitoring technique could be readily applied to other large invertebrates.

Morphometric change, distribution, and habitat use of Cook Strait giant weta (Deinacrida rugosa: Orthoptera: Anastostomatidae) after translocation to Matiu-Somes Island

Giant weta (Orthoptera: Anostostomatidae) are large flightless New Zealand insects in the genus Deinacrida. They usually survive in the absence of introduced rats and many have now been transferred to islands and areas after rodent eradications. One such transfer of the Cook Strait giant weta, D. rugosa was made from Mana Island to Matiu-Somes Island in 1996 and we investigated the sex ratio, morphometrics, growth, distribution, habitat use, nocturnal activity pattern and incidence of natural injury in February, May, September and December 2007 and February 2008. Most weta found were adults (82%), more adult females (74%) were seen than males but more male juveniles (61%) were seen than females. Weta from Matiu-Somes Island had slightly longer metatibiae than those from Mana Island. Cohorts of different-sized insects become larger in most successive samples indicating a 2-year development period following eclosion. Adults were always present but were most frequently seen in February when the smallest juveniles were also found, and large juveniles were common in September and December. Weta have spread throughout the island but were abundant over the northern half of the island with few found at the southern end. Adults and large juveniles were usually found on or near the ground whereas small juveniles were above ground on vegetation. Most adult weta were seen during the fi rst two hours of darkness in February on the ground or on short grass, and only five were on bushes. Overall, 22% of adults were injured, usually with damaged antennae or legs. Cook Strait giant weta are now so well established on Matiu-Somes Island that we consider this translocation a success.

The world's thinnest caterpillar? A new genus and species of Batrachedridae (Lepidoptera) from Sporadanthus ferrugineus (Restionaceae), a threatened New Zealand plant.

Houdinia flexilissima, gen. nov., sp. nov. is described from peatlands in the North Island of New Zealand. The extremely narrow larvae mine and pupate in the living stems of Sporadanthus ferrugineus de Lange, Heenan & Clarkson, (Restionaceae), a large endemic rush. Eggs, larvae, pupae and adults are fully described and illustrated. The systematic placement of this autapomorphic taxon is discussed in detail, and it is assigned within Gelechioidea to Batrachedridae on the basis of characters shared with a taxon currently placed in Batrachedra. Because of its morphological distinctiveness, as well as threats to the habitat of its very local host plant, H. flexilissima, gen. nov., sp. nov. is considered a species of high conservation status.