Search

Abstract Both sexes of Indian weta Gryllacropsis sp. communicate acoustically. Females lack an external ovipositor making it difficult to differentiate between the sexes in the field. There is limited ecological information on the species as it is found high up on the trunks of evergreen trees, well camouflaged, and active only at night. The present study was conducted to gain ecological information on this little known yet intriguing species. We tested the hypotheses that (a) calling activity of Indian weta is uniformly distributed throughout the year and (b) there is no difference in morphometric measurements between the sexes. The study was conducted in Bhagwan Mahavir Wildlife Sanctuary and Mollem National Park, Goa, India. Visual scanning of tree trunks followed by vegetation sampling, psychoacoustic sampling, and morphometric analyses was carried out. Resource selection function values, obtained for a total of 52 tree species from 1984 individuals, were less than 0.1 for all plant species indicating no preference by the wetas. Peak calling activity was observed in the month of November (Rayleigh's test, Z = 7.90, p

Both sexes of Indian weta Gryllacropsis sp. communicate acoustically. Females lack an external ovipositor making it difficult to differentiate between the sexes in the field. There is limited ecological information on the species as it is found high up on the trunks of evergreen trees, well camouflaged, and active only at night. The present study was conducted to gain ecological information on this little known yet intriguing species. We tested the hypotheses that (a) calling activity of Indian weta is uniformly distributed throughout the year and (b) there is no difference in morphometric measurements between the sexes. The study was conducted in Bhagwan Mahavir Wildlife Sanctuary and Mollem National Park, Goa, India. Visual scanning of tree trunks followed by vegetation sampling, psychoacoustic sampling, and morphometric analyses was carried out. Resource selection function values, obtained for a total of 52 tree species from 1984 individuals, were less than 0.1 for all plant species indicating no preference by the wetas. Peak calling activity was observed in the month of November (Rayleigh's test, Z = 7.90, p <.01). Discriminant function analysis on morphometric characters of males and females (Wilk's λ = 0.32 approx. F (4, 21) = 11.24 p <.0001, classification accuracy = 96.15%) provided clear distinction between males and females. Contribution of body weight was significant (standardized canonical discriminant function coefficients = +1) and could be used for identification of sexes in the field. These polyphagous insects provide insights on understanding ecological specialization due to host plant association, signal evolution, and mating behavior. [ABSTRACT FROM AUTHOR]

Reproductive activities are generally costly to immune responsiveness because limited resources required by reproduction are diverted away from immunity (and vice versa). Reproduction, however, is not expected to affect the immune response in males and females similarly as mating is expected to negatively affect male immunity more so than female immunity. Here, I test the phenotypic plasticity hypothesis in the Wellington tree weta ( Hemideina crassidens), a sexually dimorphic orthopteran insect that is endemic to New Zealand. My laboratory experiment showed that although males had higher rates of melanotic encapsulation than females, contrary to prediction, females were the only sex significantly affected by mating and the effect was positive. In addition to immunity differing between the sexes, immune function can differ intrasexually, particularly when males are polymorphic and different investment strategies are used to maximize fitness. Male H. crassidens exhibit alternative mating strategies that are represented by three different morphotypes. I therefore explored whether the morphs differed in their melanotic encapsulation response and whether mating affected the morphs differently. I found no difference among morphs or an effect of mating on male immune response. [ABSTRACT FROM AUTHOR]

Recognition of conspecifics is an essential precursor of successful mating. Where related species coexist, species discrimination might be important, but because related species are similar, species signal recognition may actually be low. Chemical cues such as cuticular hydrocarbons ( CHCs) are frequently used by insects to identify suitable sexual partners. We predicted that New Zealand tree weta ( Hemideina spp.), a genus of nocturnal ensiferan Orthoptera that live both allopatrically and sympatrically, use chemical signals from either frass or CHCs to find mates. In a series of six laboratory trials using both H. thoracica and H. crassidens, we found that male tree weta, but not female tree weta, occupied cavities primed with female cuticular cues more often than cavities without. However, males did not discriminate between chemical cues of male and female conspecifics, or between conspecifics and heterospecifics. In field trials, tree weta did not occupy artificial cavities primed with either female frass or female cuticular cues more often than unscented cavities. However, in both trials weta preferentially returned to cavities that had already been occupied earlier in the trials. A final field trial confirmed the presence of mixed species harems during the mating season in one region of sympatry. Our results suggest that selection on sex and species specific chemical cues that could be used to find conspecific mates is weak. Mixed species aggregations suggest that identification of conspecific mating cues has not evolved to be species specific. We infer that for male tree weta, the cost of mating with heterospecifics is likely less than not mating at all. [ABSTRACT FROM AUTHOR]

The New Zealand cave weta fauna is large and diverse but poorly described. This study aimed to improve the strategies for cave weta identification and, in doing so, build an understanding of population dynamics and distribution of the taxon across three habitat types in the Te Paki Ecological District. Species identification used morphological traits and metric analysis of specimens in pitfall traps. Although nearly half the individuals were juveniles (< 10 mm long) that could not readily be distinguished from one another, four species were identified from the larger specimens. Capture rates of cave weta varied by species, habitat, month and the interactions of these variables. Nearly half of all identified cave weta individuals in our sample were Neonetus variegatus, which was abundant across all three habitats (pine forest, native forest and shrubland) throughout the year, but were caught in pitfall traps in the greatest numbers in some pine forest sites. A species of Pachyrhamma was also abundant and showed seasonal variation in capture rate, but no adults were captured by pitfall traps. Talitropsis sp. and Pallidoplectron sp. were least frequent in our sample. Taxonomic resolution improves ecological inference, but, as with other invertebrates, trapping method and design influence sampling outcome among species. [ABSTRACT FROM AUTHOR]

Although the New Zealand ground wētā (Anostostomatidae: Hemiandrus) are widespread and abundant, little has been described of their ecology and behaviour. Within the genus several lineages have evolved with ovipositors that are unusually short for this orthopteran family. Some species with this derived morphological character also exhibit maternal care of eggs and offspring. Two new species are described here, Hemiandrus maia sp. nov. and Hemiandrus electra sp. nov. Although morphologically similar with medium length ovipositors, they are not sister taxa and live at opposite ends of South Island, New Zealand. The behaviour of Hemiandrus maia sp. nov. was studied using burrow door re-construction as a key to activity patterns. Observations at night and burrow excavation during the day were used to identify features of their behaviour. Maternal care of both eggs and nymphs was observed. Hemiandrus maia sp. nov. were shown to eat fruit, invertebrates and seeds without discrimination. http://zoobank.org/urn:lsid:zoobank.org:pub:1C7EB0D2-D01B-4D3A-B643-D17813EC2084 [ABSTRACT FROM AUTHOR]

New Zealand is home to giant king crickets called weta, which are the only insects known to consume fleshy-fruits and disperse seeds after gut passage. Although they disperse seeds in viable condition after consumption, their importance as seed dispersers is unknown. We conducted a series of field observations and laboratory experiments to investigate intraspecific variation in the capacity of Wellington tree weta ( Hemidenina crassidens) to disperse seeds of tree fuchsia ( Fuchsia excorticata). We asked three questions. How frequently do weta disperse fuchsia seeds? Do seed passage rates differ between sexes and different-sized weta? Might weta select for particular seed sizes via differential seed mortality after ingestion? A total of 2,272 F. excorticata seedlings germinated from 241 scats (i.e., faecal pellets) that were collected from the field. Experimental results showed that, on average, 15% of seeds ingested by weta successfully germinated, whereas 75% germinated in control trials. Larger weta dispersed greater numbers of seeds in experimental trials, while no differences in dispersal rates were observed between sexes. Regardless of sex and size, weta preferentially dispersed larger seeds. When interpreted collectively, results indicate that (1) weta are frequent seed dispersers of F. excorticata, although many seeds are destroyed during ingestion, (2) larger-bodied weta consistently disperse greater quantities of seeds, which is unusual in seed dispersal mutualisms, and (3) weta preferentially disperse larger seeds, suggesting that they might interact evolutionarily with New Zealand plants. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The sexually dimorphic Wellington tree weta ( Hemideina crassidens Blanchard) (Orthoptera: Anostostomatidae) is a harem-defending polygynous insect in which males use their enormous mandibles to fight conspecifics for access to harems residing in tree cavities (gallery). Tree weta ejaculates (spermatophores) do not include a nuptial meal (spermatophylax) to delay removal by females as in some ensiferan Orthoptera. Consequently, male tree weta are predicted to remain with their mates post-copula to ensure complete sperm transfer. Contrary to prediction, however, males forcibly eject females from the mating site (gallery) soon after copulation. Results suggest that forcible ejection occurs apparently because females consume the previous spermatophore if either the resident male or a rival initiates a subsequent copulation attempt. Thus, ejection appears to reduce the resident male’s risk that his ejaculate will be eaten and his mate will copulate with another male. [ABSTRACT FROM AUTHOR]

Wetanema ripariae n. sp is described from the hind gut/faeces of the threatened Raukumara tusked weta (Motuweta riparia Gibbs, 2002). W. ripariae is close to W. hula but differs most obviously by the female having a filiform tail. While the tail shape conflicts with the generic diagnosis, a filiform tail was illustrated in a juvenile of the type species. Both species may have eggs flattened on one side. [ABSTRACT FROM AUTHOR]

In species with a resource-defence (male dominance) mating system, males are expected to maximize fitness by controlling resources deemed more valuable by sexually receptive females because these sites attract more mates. Furthermore, males, which control more valuable resources should themselves be of high quality. I experimentally tested these predictions in the laboratory using the sexually dimorphic Wellington tree weta, Hemideina crassidens (Blanchard) (Orthoptera: Tettigonioidea: Anostostomatidae). Male H. crassidens use their mandibular weaponry to fight for control of harems (groups of adult females) that seek shelter in trees cavities (galleries). As predicted, larger galleries housed significantly larger groups of females and males with larger weaponry controlled large galleries significantly more often. Therefore, galleries with a larger volume are likely considered more valuable by males because they house larger harems. However, contrary to prediction, males with larger weaponry did not reside with significantly more females overall because females did not always form the largest possible groups in galleries and males with smaller weaponry were able to reside with single females in small galleries. The latter observation suggests a possible alternative mating strategy by disadvantaged males. [ABSTRACT FROM AUTHOR]

Sound production in New Zealand giant wetas (Orthoptera: Anostostomatidae) includes a femoro-abdominal mechanism, a ticking sound when alarmed (mechanism unknown) and, in two species (Deinacrida rugosa and Deinacrida parva), a tergo-tergal mechanism on the dorsal overlapping surfaces of abdominal tergites. The tergo-tergal mechanism consists of bilaterally paired patches of short curved spines on the dorsal anterior margins of tergites II–V, rubbed by opposing patches of articulated hair sensilla on the underside of each overlapping tergite. The latter are extremely robust, modified mechanoreceptors inserted at an acute angle onto raised bases which greatly restrict movement. They rub sideways against the underlying spines and produce sound during telescopic abdominal contraction which accompanies defence leg kicking stridulation. Movement analysis showed that the abdominal tergites contract asynchronously during stridulation. Sound is produced during both phases of telescoping. Femoro-abdominal sound comprises loud clicks of broadband sound principally below 10 kHz; tergo-tergal sound is a softer hiss spreading broadly from 10 kHz to the ultrasonic above 20 kHz. We propose that the tergo-tergal mechanism may have evolved under predation pressure by the ground gleaning short tailed bat endemic to New Zealand. The use of mechanosensory hair sensilla for sound production is rare in arthropods. [Copyright &y& Elsevier]

Abstract A population of Hemideina crassidens (the Wellington tree weta) was monitored over a 4-year period after the eradication of Rattus exulans (the Polynesian rat kiore) and Gallirallus australis australis (the South Island weka) from Nukuwaiata (Chetwode Islands), Pelorus Sound, New Zealand. A novel survey technique (entrance scores) was used in combination with a conventional technique (random searches for active weta) to measure changes in weta population parameters after the removal of predation pressure and to investigate impacts of exotic predators on tree weta. Tree weta density did not increase markedly over the 4-year period, but the proportion of active adults did increase. Weta were observed to move into larger and more crowded galleries (refuges), to occupy galleries closer to the ground, and to spend less time sitting in gallery entrances. It was concluded that endemic tree weta are well adapted to withstand some introduced vertebrate predators but are able to live a more “relaxed” lifestyle in the absence of this predation. The most significant change detected was in weta age structure, with adults increasing their proportion of the population. [ABSTRACT FROM AUTHOR]