New Zealand Cutworm

George Hudson described the larva of this species as follows:

The larva is rather stout, with the anterior segments wrinkled. It varies much in colour; the dorsal surface is usually reddish-brown; the lateral line is broad and black; a series of subdorsal stripes also black; the ventral surface is green. Sometimes these markings are hardly visible, and the larva is entirely green, whilst occasionally the brown colouring predominates. Walker in his original description of I. mutans described the adult of the species as follows:

Male and female. Pale cinereous. Third joint of the palpi cylindrical, full one-third of the length of the second. Antennae of the male minutely ciliated. Thorax with a black curved band in front. Fore wings with black marks along the costa; most of the disk clouded with fawn-colour and with blackish gray; lines almost obsolete, except the submarginal one, which is distinct, whitish, slightly undulating, bordered on each side by black and brown, and interrupted by the black veins; a black discal stripe, dilated towards its tip, and widely interrupted by the space which includes the black-bordered claviform spot; orbicular and reniform spots distinct, partly bordered with black, the former oblique, a little more than half the size of the latter. Hind wings cinereous, with whitish ciliae. Var. …

This species is endemic to New Zealand. I. mutans can be found throughout New Zealand, including from Three Kings Islands down to Stewart Island. However this species is not found in the Chatham Islands.

The larvae of I. mutans was described by Hudson as being sluggish. I. mutans adults are on the wing all months of the year. This species is attracted to light and have been collected via a mercury vapour light trap.

The larvae feed on a variety of herbaceous plants including those used to create pasture for stock, weeds such as Pilosella officinarum, as well as crops such as turnips, peas, wheat, and the leaves and fruit of apple trees. This species is therefore sometimes considered an agricultural pest. I. mutans pupates on the ground or on moss. The length of time this species in the pupal state depends on the season in which it pupates as well as what part of the country. If in summer it can be a short period of time, but if in autumn the adult does not emerge until the following spring. In the North Island it is thought that I. mutans may have up to four generations a year where as in the South Island this is likely to be reduced to two.