CATERPILLAR, SUBTERRANEAN GRASS
The larval stages of the moths commonly called porina moths (after the earlier generic name Porina) are important pasture pests in New Zealand. They live in tunnels in the soil during the day and feed at night at the surface of the soil on grass foliage. The damage done by them to pastures is comparable to that caused by the grass grub. Like the grass grubs, the subterranean grass caterpillars have adapted themselves very successfully to the introduced grasses which now dominate the grasslands of New Zealand. The life cycle is an annual one. Eggs are deposited on grasses in October to January, and the caterpillars are active from December to September. Adults appear in October to January. They do not damage plants but are attracted to light in great numbers and, in the South Island particularly, are a predominant feature of the insect life of early summer. Control is successfully carried out by the application of insecticides to the pastures. Many species of grass caterpillars are known, but only two or three are of importance as pasture pests. Other species are particularly prone to attack by the fungus Cordyceps. The caterpillars are attacked in the ground and, when all the caterpillar tissue is replaced by the fungus, a spore-bearing stalk is produced and protrudes above the ground. In this state the organism is called a vegetable caterpillar.
by Roy Alexander Harrison, D.SC., Senior Lecturer in Agricultural Zoology, Lincoln Agricultural College.