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Common Tussock

 

Argyrophenga antipodum

Scientific Classification More info Family Nymphalidae SubFamily Satyrinae Tribe Satyrini SubTribe Coenonymphina Genus Argyrophenga Taxon antipodum

Also Known As;

Tussock Ringlet

Description

A native species of Butterfly that still needs farther study & whose life history is not well known. (See bottom of page for unanswered questions). Suspected lifecycle is one year in most of its range & maybe longer in the sub-alpine areas of range. It is very well camouflaged with closed wings, as they have silver streaks on the underside of the back wings that blend in with grass blades. It's range overlaps Janita's Tussock in it's eastern & northern range. Generally in most of the shared range, Janita's Tussock will stay above the beech forest line, whereas the Common tussock will stay below this altitude. but when the forest is absent, Janita's Tussock tend to fly in areas of Chionochloa - large Snow Tussocks, whereas the common Tussock will fly in areas of Festuca & Poa - small Tussocks & other grasses. The ovum & pupa are nearly the same on all 3 Tussock Butterfly species.

Ovum  In English

Ovum are either laid singularly on the foodplant or dropped when flying above the foodplant. Uniform white to pale-green for first 2 days, then become mottled brown in colour. Just before hatching the general colouration becomes silvery due to a layer of air between the shell & the larva inside. Barrel-shaped with 15-18 vertical ribs. They hatch after approx 6 days. Upon hatching, the larva chews around the crown & pushes it up to leave, then most of the shell is eaten by the newly hatched larva for it's first meal.

Larvae  In English

It is sleek leaf-green, yellow-brown or reddish-brown with yellow stripes down the side, fine setae, tapers towards the tail & has a distinguishing predominant dark mid-dorsal stripe which contrasts vividly against the body background colour. It has a bifid head & tail. They have 5 instars. They usually spend their resting time head-down below the notch they are presently eating. This can take several days as they are slow eaters. They eat through the leaves of Tussock or grass leaving small elongated notches along the margin. As they are elongated larvae & almost the same colour as the leaves, they are very well camouflaged. They are very similar to the Forest Ringlet larvae, but unlike the Forest Ringlet, the first instar larvae have a pale-brown head instead of a black head. Tussock larvae also have setae which are absent on the Forest Ringlet. Before pupating, they spend about 2 days head-down on a leaf with their anal prolegs attached to a silken pad, however they use all their prolegs to hold onto the leaf unlike the Forest Ringlet, which hangs free. Grows up to 28mm when fully grown.

Pupa  In English

More variable in colour then the other Tussock Butterflies, it ranges from a pale-green through dark-green to light-brown with a forked head. Larva's colours doesn't necessarily correspond to pupa colouration. It is elongated & attached to Tussock leaves by cremaster & usually lies flat along a blade for disguise in the heart of the plant. Pupation lasts between 12 to 18 days.

Imago  In English

The imago has a 31-46mm wingspan, male average is 44mm & female average is 40mm. Flight is weak & takes on a hopping appearance. They quite often land roughly & then have to find their footing. In full sun they keep their wings wide open, but quickly close them if there is any disturbance, including wind. The male is slightly larger & have red-brown wing patches. The female has a light yellow wing patch & whitish borders to wings. Both genders have black spots with 2 white ocelli on the forewings & several black spots with 1 white ocelli each on the hindwings. Even so the ocelli are on the upper wing surface, they show through to the underside. The orange wing patches are larger & lack the brown scales along the veins then those found on Janita's Tussock or Harris's Tussock. The sexual dimorphism results in the males having deeper colouration & the females having paler colouration then the other 2 Tussock Butterflies. However at higher altitudes the males become paler & the females become more intense in colouration, especially in central & western Otago. The definitive feature of the Common Tussock is that it has a 7th silver streak at the front of the underside of the hindwing, which meets a silver border which continues around to the rear of the hindwing. This silver border stops farther back on Harris's Tussock. Males appear more common, but is probably due to them spending more time on the wing.

Habitat

Most common in South Island Tussock at altitudes of 500-1600m. However it is found from sea level to 2000m. In it's lowland ranges, it's still a common Butterfly in swampy areas & course grasslands.

Status & Distribution

Widespread Found in the Southern Alps on eastern side of main divide, from the inland valleys of Marlborough to Southland. It increases in numbers in Otago & Southland. It never crosses to the western side of the main divide since it's too wet there. It has declined due to improved pastures for farm animals & burning of Tussock areas to improve the palatability of Tussocks for Sheep.

Food Plants

Silver Tussock (Poa cita), Red Tussock - Haumata (Chionochloa rubra), Festuca, Agropyron, Snow Tussock (Chionochloa spp), Other Tussock's (Poa spp) & some introduced grasses. It's suspected other Tussocks & grasses are suitable foodplants, but since the larvae are hard to find & the grasses are equally hard to identify, it maybe a while before there is a comprehensive list.

Lifecycle

Note: there is possible inaccuracies for the egg, larvae & pupation stages.

Unknown Facts

The Common Tussock is a species of Butterfly that still needs farther study.

Unanswered questions are;

• How long is the period the ovum take to mature?
• What are the 'other' Tussocks & grasses they use for foodplants?
• Their distribution?
• Their lifecycle - is it different from other the other Tussock Butterflies?
• Is there a short summer generation?
• Altitudinal variation?
• Courtship behaviours?
• Do they hybridise with other Tussock Butterflies?
• Is there a better way of defining the habitat distinction between Janita's Tussock & the Common Tussock?
• Any correspondence between black spot frequency on the wings to the location?

Please contact nzButterfly.info if you can answer any of the above questions.

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