Neocicindela tuberculata

Neocicindela tuberculata is a species of tiger beetle endemic to New Zealand and is sometimes referred to as Tuberculate tiger beetle or Common tiger beetle. It was first described in 1775 by Johan Christian Fabricius, making it the first ground beetle to be described from New Zealand. The species has been suggested to be roughly 0.92 million years old. Adult species prefer clay banks in summer and are good predators when in comes to insects.^[1] Neocicindela tuberculata are found throughout New Zealand and can be seen on hot sunny days on clay tracks or sandy areas. As well as running it can also fly. The adult beetle is approximately 2.5 cm long, and is greenish in colour with yellow markings on the side of the elytra. It eats other insects as food.^[2]

This tiger beetle was first described as Cicindela tuberculata in 1775 by Johan Christian Fabricius in his first major publication, Systema entomologiae.^[3][4] This is regarded as the first description of a ground beetle from New Zealand.^[5] The species was featured in another taxonomic revision in 1846, although little new information was presented.^[6] In 1877, Thomas Broun described the species again as Cicindela huttoni, named after entomologist Frederick Hutton. It was named as a different species because Broun considered it to be less robust in form.^[7] This was later recognized as a synonym in 1936.^[8]

In 1963, the species was transferred to the newly created Neocicindela, which contained all of New Zealand’s tiger beetle fauna initially.^[9] This genus was demoted to subgenus in 2001 and the species was reassigned to Cicindela by André Larochelle and Marie-Claude Larivière. The common name of "Tuberculate tiger beetle" was also suggested for the species (although "Common tiger beetle" is also used).^[5][10] It was most recently revised in 2013 by Larochelle and Lariviere, who reassigned it to the Neocicindela genus.^[10]

A 2011 study examined the genetic relationships of New Zealand's tiger beetles. The combined sequences of cytochrome oxidase I, cytochrome b and 16S rRNA suggested that Neocicindela formed a clade (group of organisms that comprise all descendants of a common ancestor) that was distinct and separate from Zecicindela (which was at the time, identified as Neocicindela). It found that within the dataset, N. tuberculata is most closely related to Neocicindela latecinta, from which it diverged around 0.92 million years ago.^[11]

Neocicindela tuberculata is best distinguished from all other species of Neocicindela by the combination of a single setiferous pore (one pore with a long hair sticking out of it) on antennae segment one and the colour pattern of the abdomen.

The beetle is about 9–12mm (0.35–0.47 in) in length with a dark brown head and pronotum. The antennae and femora are dark, whilst the tibia and tarsi are pale. The first antennal segment also has anywhere between five or nine setiferous pores

The elytra (wing coverings or hardened for wings) colour background is dark brown with some tinges of velvet black and moderately wide. The dark areas of the elytra are shiny, somewhat metallic and are covered in small green metallic punctures. The elytra have numerous distinctive pale yellow markings. The humeral lunule (marking at the upper corner of the elytra) is fused with marginal line (marking along the middle margin of the elytra). The middle band of the yellow marking distinctly sticks out and is angled towards the apical lunule (part of the yellow marking sticking out near the tip of the abdomen). The marginal line is separated from the apical lunule. The shape of the elytra also begin to widen behind the middle.^[10]

Larvae are 20mm in length when in their final instar before moulting. The head and prothorax form a single circular flattened shape. The mandibles are sickle shaped. The labrum of the larvae is well developed and projects from the head of the insect. The tarsi of the legs are two jointed and have double claws. The larvae slowly widens after segment five and segment 9 have a pronounced dorsal hump.^[12]

Neocicindela tuberculata are found endemic to New Zealand where they are found across all regions of the North Island and are also found in the Marlborough and Tasman regions of the South Island.^[5] It is most often found on the lowland areas of these regions.^[5]

These beetles are found in most habitats but generally prefers open areas.^[13][14][5] N. tuberculata is a diurnal (active in daylight/sunshine) insect so would be most benefited by areas with large amounts of sunlight.^[15][5] They are also generally found in physiological and ecologically uncomplicated areas.^[15][13] The larvae of N. tuberculata prefer to dig their burrows in on dry soil, particularly exposed sand or peaty soil^[16] as well as clay banks.^[5]

Mating for N. tuberculata occurs during February^[5] and after this occurs the female lays her eggs in the soil by drilling many holes with her ovipositor, and laying one egg in each hole.^[17] These holes are initially big enough for the larvae, however as the larvae grow, so too must the hole. As they develop and grow in size, the larvae will make the hole bigger, therefore the size of the burrow will determine the age of the larvae.^[17] The larval stage depends on not only the species of Cicindela, but also the frequency of food, and the climate, however the larval stage will generally only last for one to two years depending on these resources.^[17] Once the larvae are ready to pupate they do so and this stage is very brief,^[17] beginning in February, which is when the larval population declines to a point where they are no longer seen.^[5] When it is pupating, the larvae plugs the hole of its burrow and descends to the bottom of the burrow where it digs a side cavity to pupate in. The adults will emerge in spring or early summer, where they will mate and die before autumn is finished.^[17]

Both the adult and the larvae of Neocicindela tuberculata are predators of other insects. The adults of N. tuberculata eat mainly caterpillars and flies,^[5] and it has been said that the “mean mandible length (chord) is directly related to mean size of prey captures by tiger beetles throughout the world”.^[15] Food data and mouthpart morphology of the tiger Beetle genera, shows that they are opportunistic predators that can feed on a variety of small prey.^[5] The adults use their long legs, and therefore running capabilities, to catch their prey, along with their short flight capabilities.^[17] The larvae dig vertical burrows in the ground^[18][5][17] which can be up to 15 cm deep^[5][17] and are kept constantly clean and smooth by the larvae.^[18] Once the larvae have burrowed into their holes, they sit at the entrance in such a way that their head is at the entrance of the hole and their body fills the rest of their hole.^[18] Once the larvae spots prey they determine the best way to catch it based on its size, by either going back into their burrow and seizing it when it falls in, or by darting out and seizing the prey that way.^[18] The larvae generally feed on flies and other small invertebrates,^[5] similar to what the adult feeds on.

Neocicindela tuberculata is preyed on by a number of different birds such as kiwis and magpies.^[5] It is also preyed on by Asilids, better known as Assassin flies or Robber flies. To protect itself from these predators the adult emits a musky smell when it is disturbed.^[5] C. tuberculata is also part of the only beetle family (tiger beetles) that are capable of instantaneous flight and there is a possibility that they also use this to evade predators.^[18] The tiger beetle family are generally the fastest running beetles because of their long legs.^[18] This could also be used as a method of evasion from predators.

• Scientific literature discussing Neocicindela tuberculata in the Biodiversity Heritage Library
• Citizen Science observations of Neocicindela tuberculata
• Neocicindela tuberculata discussed in RNZ Critter of the Week, 10 Jul 2020