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Nascioides enysi (Sharp) is one of New Zealand's two buprestid beetles, also known as jewel beetles due to their colourful appearance. The other New Zealand buprestid is Maoraxia eremita (White). The habitat of the beetle is the Nothofagus beech tree species where adults are found during the summer period with high activity at times with lots of sun.
| Nascioides enysi | |
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| Genus: | Kerremans, 1903
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| Species: | N. enysi
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| Binomial name | |
| Nasciodes enysi Sharp, 1877
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Description
[edit]N. enysi larvae are a creamy white colour and when fully grown are about 20mm long and 5mm wide, recently hatched larvae are about 2-3mm long and 0.3mm wide.[1] The head is deeply embedded in the prothorax and only the mandibles extend out the front.[1] The prothorax is widened and flattened compared with the rest of the larval body with a V-marking on the top side and a T-marking on the underside.[1] The segments directly after the prothorax taper sharply to the abdomen which is about half the width.[1]
The adult beetle of N. enysi ranges from 7-10mm long and 1.7-3.2mm wide.[1][2] The colour of the beetle is primarily blackish with a metallic purple and green colour from various angles with some identifying sexual dimorphic features.[1][3] The elytra are ribbed and tapered at the end with two yellow/orange spots of a rough oval shape at about equal thirds lengthwise.[2] The front most spots are angled inwards with the back end in the centre, the back most spots sit across the width of the body.[2] The head of the beetle is flat without mouthparts protruding out the front, rather placed underneath.[2] The front margin of the head is concave in the middle with the forehead being slightly swollen.[2] The beetle has small hairs called setae on many parts of the body including head, antenna, thorax, and elytra.[2]
Sexual Dimorphism
[edit]There is distinct sexual dimorphism between the males and females of N. enysi easily identified.[1][3] The males have a red metallic colour on the front of the head which is visible from front on.[3] Further less obvious colouration differences are observable.[3] Male front sides of the femur and tibia of the first pair of legs are a metallic bronze and green, the remaining legs are a dull metallic purple.[3] The antennal segments are a metallic blue, accept for the basal scape segment which is the metallic red colour of the front of the head.[3] The male basal segment of legs is a metallic blue.[3] Adult females lack the metallic red colouration of the face, instead is the dull metallic purple of rest of the body.[1][3] All the female legs and antennal segments are the dull metallic purple of the body.[3]
Distribution
[edit]The genus Nascioides has 18 species, 17 found in Australia and one in New Zealand. Nascioides enysi is found only in New Zealand, occurring in both islands in all species of New Zealand Nothofagus, beech trees.[4] N. enysi closely resembles N. quadrinotatus, a species found in Tasmania and southern Victoria but is not found in New Zealand.[4] N. quadrinotatus can be differentiated by the colouration on the heads of adult males.[2] N. enysi have a metallic red colour whilst N. quadrinotatus has a metallic blue colouration.[2] N. tillyard is the only other Nascioides species associated with Nothofagus and is not found in New Zealand.[2]
Life Cycle
[edit]Emergence of N. enysi from pupal cavities in Nothofagus bark occurs from late October to early February with a peak in the second week of November.[5] Adult beetles are short lived and rarely seen after the third week of February.[5] Adults construct oval exit holes 2.5mm x 3.6mm in size on the bark surface.[1][5] After forming these holes, they can return to the pupal chamber until emergence conditions of temperature and light are ideal.[5] Daily emergence occurs between 9am and 6pm or when temperature exceeds 32 degrees Celsius.[5] Peak emergence during the day occurs at 12 pm and at 4:30pm with greater emergence of females between 11am and 1pm and male emergence dominating at other times.[5] Overall emergence sex ratio works out to be about 1:1. In lower temperature many adults, mainly females fall to the ground and within a few hours die.[5]
After emergence first flights are rarely more than 30m followed by short flights and crawling to reach food sources of Nothofagus leaves.[5] A starved beetle will survive 2-10 days, while a beetle with sufficient feed has a lifespan of 36 – 74 days.[5] After the first day of feeding a pattern of behaviour occurs dependant on temperature. Below 10 degrees Celsius beetles are inactive, 10-12 degrees Celsius beetles make short flight and crawling, 13 degrees Celsius feeding occurs, 16 degrees Celsius mating will commence and above 22 degrees Celsius oviposition takes place.[1][5] Activities described also occur above the listed temperatures.
Mating takes place between 11am and 6pm after at least 3 days of feeding.[5] Females require a period of feeding and sun basking before mating will occur.[5] Mating events can vary from 1 minute to 5 hours, but oviposition does not occur until at least 1 mating period of 20 minutes commences, indicating a minimum requirement for successful mating.[5] Males and females will mate several times without being selective of the partner after the initial oviposition.[5] Oviposition will occur after a week from emergence and 2-4 days after copulation where temperature is above 22 degrees Celsius or after 11am.[5] Temperatures between 22 and 24 require full sunlight exposure for oviposition.[5] At temperature up to 30 degrees Celsius oviposition occurs in shaded areas.[5] Despite needing dead material for complete larval development, females will deposit eggs in live trees during epidemics with the hope that during the lifespan of the first larval stage the tree will die.[4]
The eggs appear a cream or whole colour when first deposited at a size of about 0.85mm – 1.15mm long by 0.45mm – 0.65mm wide.[5] Eggs are laid either individually or in groups of 2 – 3 under bark scales, in narrow openings or breakages, preferences to roughened parts.[1][5] Female behaviour is characteristic when ovipositing, they walk hesitantly over the bark surface testing with the flexible ovipositor for suitable sites.[5] When a site is found the ovipositor is inserted at full length and the beetle remains stationary for about a minute, then runs away from the site.[5] Females may return to the same site to deposit another egg, or an egg may not be laid on every insert.[5] The incubation period of the egg is about 34 days with a range of 29-39 days with a temperature range of 5 – 29 degrees Celsius.[5]
There are 6 larval stages in N. enysi.[1] After hatching from the egg, the larvae enter the bark and mine to the phloem where it feeds until ready to moult.[5] With each larval stage the mine increases in size, following a meandering pattern, rarely straight.[5] When ready to pupate the sixth larval stage forms a pupal chamber in the bark where it stops feeding and begins the transformation into a pupae then adult form.[5] The pupal stage can vary from 24-44 days, averaging 29 days.[5] Development from pupae to adult takes about 26-29 days where the adults will then rest in the chamber before boring out of the bark.[5]
The whole life cycle can be over one year in thin bark or two years in thicker bark, however the size of adults does not seem to vary from one or two-year cycles.[1][5]
Interactions
[edit]Larvae of N. enysi feed on the outer layer of the phloem in the first larval stage, awaiting the death of the inner phloem.[5] The larvae do not have the ability to cause the death of the inner phloem, rather act as opportunists when it happens due to other factors such as wind damage.[5] The later larvae stages feed on the old dead tissue of this inner phloem.[5]
There is a preference of feeding shown to older leaves of Nothofagus species with no preference between Nothofagus species.[5] No damage has been observed to others common species such as Coprosma spp., Quintinia sp., Weinmannia racemosa Linn, f., Myrtus bullata Soland., and Neopanax spp.[5] Buds and new leaves are rarely damaged by N. enysi, due to the adult beetles’ ability to cling to the margins of the stiffer older leaves, beetles cannot get sufficient foothold on softer leaves for feeding to occur.[5] On average an adult beetle consumes about half the average sized Nothofagus fusca leaf a day with the damage spread over multiple leaves.[5] Damaged leaves rarely fall prematurely from the living tree except when most of the leaf has been destroyed, therefore the beetle herbivory has minimal impact on these trees.[5] The lifespan average of 50 days results in the average adult beetle consuming about 20-25 leaves in its lifetime.[5]
There is no recorded natural predation on the adult beetles of N. enysi. Larvae of N. enysi are have two natural predators, the first being the braconid wasp Doryctes pallida and second being the colydiid beetle Bothrideres obsoletus.[1][5] D. pallida can parasitise up to 70% of the larvae reaching later stages of development during outbreaks of the buprestid beetle.[1][5] B. obsoletus is a generalist predator and has less direct impact on N. enysi.[5] In thick barked trees in cold conditions the larvae are susceptible to a parasitic fungus from the Entomophthoraceae family.[5] Larval populations can be reduced by up to 90% from the fungal infection.[5] Intraspecific competition in large larval populations causes a reduction in adult emergence.[5] When eggs per square foot exceed 300, only 40 adults emerged, whereas when eggs per square foot is only 10 more than 8 adults emerge.[5] A defence sap response from host trees can flood larval chambers from more vigorous trees resulting in death of the early stage larvae.[1]
Further Information
[edit]Historically, it was thought that Nascioides enysi caused damage to Nothofagus trees which raised concerns of tree mortality for forestry.[1][4] It has now been revised and found that although the first larval stages can survive in the outer phloem of living trees, for complete development to occur they require dead phloem material to feed on.[1][5] This dead material cannot be created by N. enysi and is caused from other agents such as tree fall from wind damage or other invertebrate species such as the Platypus beetle which can penetrate the inner phloem areas.[5]
Category:Endemic fauna of New Zealand Category:Beetles of New Zealand
- ^ a b c d e f g h i j k l m n o p q r Milligan, R.H. (1985). "Beech buprestid". Forest and Timber Insects in New Zealand. 63 – via Scion.
- ^ a b c d e f g h i Williams, G.A. (1987). "A Revision of the Genus Nascioides Kerremans. (Coleoptera : Buprestidae)". Invertebrate Taxon. 1: 121–45.
- ^ a b c d e f g h i Stuart, A.M. (1955). "A note on secondary sexual dimorphism in (Sharp), (Coleoptera, Buprestidae)" (PDF). N.Z. Entomology. 1: 14–15 – via BUGZ.org.nz.
- ^ a b c d Dugdale, J. S. (1966). "Nascioides enysi and beech mortality". Forest Pathology (Entomology). 14. doi:10.7931/DL1-FPR-14 – via Landcare Research.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au Morgan, F.D. (1966). "The biologyand behaviour of the beech buprestid, (Sharp) (Coleoptera:Buprestidae) with notes on its ecology and possibilities forits control" (PDF). Trans, roy. Soc. N.Z., Zool. 7(11): 159–170 – via BUGZ.org.nz.