Costelytra zealandica
| Costelytra zealandica | |
|---|---|
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Family: | Scarabaeidae |
| Subfamily: | Melolonthinae |
| Genus: | Costelytra |
| Species: | C. zealandica |
| Binomial name | |
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Costelytra zealandica (White, 1846) |
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| Synonyms | |
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Rhisotrogus zealandicus White, 1846 |
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Rhisotrogus zealandicus White, 1846
Costelytra zealandica, commonly known as grass grub, is a scarab beetle that is endemic to New Zealand and is a prevalent pasture pest.
C. zealandica was originally described by the British entomologist Adam White as Rhisotrogus zealandicus from a specimen obtained during the Ross expedition.
New Zealand grass grubs are one of the most common insects in New Zealand. Grass grubs belong to the holometabolous insect group, this means that they have a life cycle with four stages: egg, larva, pupa, adult. The adult beetle can grow up to a mature length of 13 mm. It has a shiny brown colouring with a thick wing covering called an elytra. Adult beetles also have a prominent plate like piece covering the thorax called the pronotum. These adults can be seen flying in the evenings during the summer months.
Female adults lay up to 100 eggs at a time into wet or loose soil, 10–15 days after mating. Eggs are small, white, oval shaped and around 1.5 mm in diameter. 3–4 days after being laid, the eggs turn smooth, spherical, and start to swell by absorbing moisture. Once the eggs are mature they turn a dark brown/black colour.
On hatching larvae have a whitish/grey C-shaped segmented body, with a darker coloured head and dark brown jaws (mandibles). The larvae have three pairs of legs (true legs) attached to the underside of the segment behind the head, called the thorax. The length of the larvae ranges from 5 mm, when newly hatched, to 25 mm at larval maturity. Newly hatched larvae weigh 2–3 mg and grow up to 200 mg. The most obvious characteristic of larva is that the abdomen is very swollen and looks a lot bigger than any other part of body. There are many thin fine hairs along both sides of the body, especially around the abdomen. Occasionally grass grub larvae can be found that are purple/yellow or green in colour, these are diseased.
The pupae start off the same creamy white colour as the larvae, but slowly turn to a dark brown during pupation. They have a soft body and are generally shorter and thicker than the grass grub larvae, they grow to between 10–30 mm in length. The pupae have a thin translucent skin called the epidermal layer, through which the developing wings and legs can be seen.
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Wikipedia