ON THE STRUCTURE, LIFE‐HISTORY, ECONOMIC IMPORTANCE AND DISTRIBUTION OF THE COCKSFOOT MOTH, GLYPHIPTERYX FISCHERIELLA , ZELL.

SUMMARY. The Cocksfoot Moth ( G. fischeriella , Zell.) is a small moth (wing expansion 7 1 / 2 ‐ ‐ – 8 1 / 2 mm., body dark fuscous, front wings coppery brown, with five silvery streaks along the costal margin. The moth is diurnal in habits, bright warm weather greatly favoun its activities, and on such days from the last week in May till the third week in June it is very common in the field on the nettle and gorse bushes and on flowering stalks of cocksfoot. The eggs are deposited as a rule singly at the base of a seed in the second and third weeks of June, and hatch in from ten to fifteen days' time. The larva which does the sole damage is small glassy white when newly hatched, but assumes more and more of green colour as it feeds and grows. When full grown it measures about 6 mm. in length. There are four larval instars altogether. Immediately after hatching the larva begins to bore into the seed on which it was hatched. The injury takes the form of a small circular bole through which it enters and feeds on the kernel. There is always one entrance hole and only one in each seed which also serves as the exit. After about four weeks' feeding, when the larva is full grown, it either leaves the food plant and crawls away in search of winter quarters, or remains inside the hollow husk of the seed which previously served 86 its food. In the former case, it spins a small, oval elongate, dirty white, silken cocoon in which it hibernates during the next nine months prior to actual pupation, while in the latter, instead of constructing a cocoon, it simply seals the entrance hole with a thick silken web. In captivity, under laboratory conditions, a large number of larvae, by cutting small holes, entered the dry hollow stalks of the cocksfoot plants and constructed cocoons therein. Pupation takes place in April or early in May, the pupal period extending over three or four weeks. There is only one generation in a year. As regards the food plants it was found that indigenous plants of cocksfoot were attacked much more heavily than the foreign “nationalities,” as is shown in the following table: A suggestion is made that the moth selects the panicle on which it lays its eggs, finding the indigenous plants more attractive than those of the foreign nationalities. It appears that the selection is made by the moth rather than by the larva. Samples of seeds obtained from different places in England, Scotland and Wales showed that the pest was generally distributed all over the island; almost all samples examined were found to have been attacked. The larva is so effectively protected within the seed that no internal parasite was found to attack it. An effective method of obtaining seeds free from this pest is to place them in an airtight chamber, heat up to 60°C., and leave there for twenty‐four hours. This temperature kills all the larvae, and, on the other hand, does no harm to the germinating power of the seed.