A preliminary study of the biology of Haplothrips niger Osborn, and associated thrips, on red clover in New Zealand

Abstract

The primary aim of this investigation has been to study the biology of Haplothrips niger on red clover in New Zealand. The various aspects of the biology which it was intended to study were: i. A full description of all stages of the insect. This section is illustrated with drawings and photographs. ii. The life cycle of the insect. iii. Factors affecting the life cycle. iv. The damage done by thrips feeding on red clover heads. v. The level of infestation in the season under review. vi. The effects of this level of infestation on the seed set by, and harvested from, infested clover heads. vii. The effects of different levels of infestation artificially produced in laboratory studies. At the outset of the investigations it was not known whether ,any other species of thrips were associated with H. niger in the red clover head. Having regard to the difficulties of identification of these insects, it was decided to collect and identify thrips from a wide range or plants and flowers. This was done prior to the clover flowering season so that during that relatively short period, any thrips species collected might be readily identified. The results of this work are included in order to place on record the species of thrips so far found to be present in this country. The investigations were carried out at Canterbury Agricultural College during 1948 and 1949. The investigations into artificial infestation were carried out in the insectary at the College. Field investigations were made at Lincoln and Timaru during the 1948-1949 harvest season. A few crops were inspected in the Wairarapa and Hawke's Bay districts during April 1949. Thrips were collected from all places visited during the two years.