DESTRUCTION OF EARWIGS

Hokitika Guardian, 12 August 1931, Page 7

DESTRUCTION OF EARWIGS

PARASITE ESTABLISHED. SUCCESS OF CAWTHRON INSTITUTE. NELSON, Axi S . 9. The earwig, that vicious and übiquitous enemy of orchadist and gardener, is to have an enemy opposed to him which may, control him even to the point of extermination, for experiments designed to establish the tachinid fly as a parasite to him have at last been brought to fruition by the entomological staff of the Cawthron Institute after patiently waiting and working for the past seven years.

It had been known for a long time that this fly, which resembles the ordinary house fly in size and appearance, was definitely a parasite of the earwig in Europe, but the problem was to get It to breed in New Zealand. It was found that to bring consignments of them from one hemisphere to another upset the normal cycle of life with the result that they would not breed. To harmonise this cycle was the task which confronted the entomologists in Nelson, but success seemed elusive through the years. NEW TECHNIQUE.

Dr David Miller, chief entomologist to the Institute, relates how, prior to last year, the work having been a failure, they had decided to discontinue it, when news came of a new technique for the handling of parasites which had been employed with success by overseas scientists. The institute then resalved to persevere, using the new technique. Mr C. IT. G. Fraser, one of the younger members of the staff, was put in charge and success has at last been achieved.

The story of how this was done, ns told by Mr Fraser himself, is instructive. Ever since December, 1923, he said, the institue has been receiving consignments of these insects from the Farnham Royal Laboratory, in England. To explain the difficulties confronting the scientist it was necessary to know something of the habits of the tachnid fly. In Europe this insect deposited its larvae in the presence of earwigs. When the maggots hatched they crawled on to the host (the ear-' wig) and entered the abdomen or thorax. There they proceeded to absorb the body and blood of the earwig without any apparent effect on that insect until they were developed enough to leave, when they set about devouring all- the earwig’s internal organs, leaving only the shell of this insect behind. Then they pupated and went into the fly stage. CHANGE OF SEASONS.

The flies destined for New Zealand were collected in England and sent to the in sectary at tile Earnham Royal Laboratory and fed there till tile eggs reached tile maggot stage. They mere then collected and forwarded to the instiutOi »'Rut the* - trouble''“'Wose through the parasite reaching the Dominion towards winter go that the flies began to emerge shortly after arrival. This, of course, interefered with their natural cycle and the difficulty had been in getting them to mate and also in producing living conditions approximating to the northern summer. Finally, by exposing them to direct sunlight in a warm sheltered spot the flies were mated. This achieved, it was considered necessary only to keep them living in an atmosphere where the temperature and humidity . approximated to summer conditions. Under such conditions were the flies matured for the first time in New Zealand. y THOUSANDS OF EARWIGS PARASITED. The females oviposited in the presense of earwigs. So far over one thousand Nelson earwigs have been parasited. The flies have done their work well and there is every reason to believe that these parasites can be raised in this country and distributed, much to the discomfort of the earwig, and the satisfaction of the fruitgrower.