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Janita's Tussock

 

Argyrophenga janitae

	Ovum Larvae Pupa Imago Classification Habitat Food Plants Lifecycle Unknown Facts

Distribution & Status Common Found in the eastern Southern Alps from Nelson to north Otago. It has declined due to improved pastures for farm animals and burning of Tussock areas to improve the palatability of Tussocks for Sheep. Observations map

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

Also Known As;

Tussock Ringlet, Eastern Tussock

Description

A native species of Butterfly that still needs farther study and whose life history is not well known. (See bottom of page for unanswered questions). Suspected lifecycle is one year in most of its range and maybe longer in the sub-alpine areas of range, since third, forth and fifth instar larvae have being found in early spring in Tussocks adjacent to snow patches after overwintering. 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 Harris's Tussock in the Tasman Mountains where both species fly together. It shares most of its range with the Common Tussock where, Janita's Tussock will stay above the beech forest line and 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 and Poa - small Tussocks and other grasses. The ovum and pupa are nearly the same on all three Tussock Butterfly species. it's named after Janita Craw who assisted her husband in identifying this Tussock Butterfly as it's own 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 and the larva inside. Barrel-shaped with 15-18 vertical ribs. They hatch after approx 6 days. Upon hatching, the larva chews around the crown and 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 with slightly darker stripes down the side, tapers towards the tail and has distinguishing white setae on the main part of the body and longer setae on the rear end. It has a bifid head and 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 and 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

Greenish with varying markings and a forked head. It is elongated and attached to Tussock leaves by cremaster and 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 31-45mm wingspan, female average is 40mm and is usually slightly larger wingspan then the males, however those around the Dun Mountain area of Nelson are smaller, this maybe due to a mineral belt that also seems to have a dwarfing effect on Forest Ringlet as well. Flight is weak and takes on a hopping appearance. They quite often land roughly and 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. I have observed that if faced with danger while resting or just landed near the top of a Tussock, it will flash its wings quickly (like an Admiral or Monarch), then immediately as drop low as possible into the Tussock with its wings closed. Historical literature notes similar behaviour while flying. Both genders have black spots with 2 white ocelli on the forewings and 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 male has a long slender abdomen while the female has a short stout abdomen. Differs from the Common Tussock by having heavily outlined veins on both wings and differs from Harris's Tussock by having larger orange patches on both wings. There is hardly any sexual dimorphism in lower altitudes, however in higher altitudes the males become paler and the females become brighter. The definitive feature of Janita's Tussock is that it does not have the silver margin to underside of the hindwings like the other 2 Tussock Butterflies. Males appear more common, but is probably due to them spending more time on the wing.

Habitat

Montane to subalpine tussock, between altitudes of 500-2000m.

Food Plants

Snow Tussock (Chionochloa spp)

Lifecycle

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

Unknown Facts

Janita's Tussock is a species of Butterfly that still needs farther study.

Unanswered questions are;

• How long is the period the ovum take to mature?
• Do the larvae eat anything but Snow Tussock (Chionochloa spp) or do they share other Tussock 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 and the Common Tussock?

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

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