Transactions of RHASS Volume 1940 - Page 056
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| Year | 1940 |
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INSECT AND OTHER PEsrs or 1939. LEATHER J ACKETS. The Leather Jacket is another important pest that is destructive to crops, particularly cereals, which follow the breaking of grass land. So well known is this insect 1 that there is scarcely a farmer but has had some. experience of its activities. 111 point of economic importance, the ‘Grnb,’ or Leather Jacket, does not fall far short of the Wireworm, and like the latte‘ attacks a wide range of plants. Unlike the Wireworm, however, which, we have seen, requires four or five years to complete its development, the Leather Jacket requires only one. Thus the Leather Jacket is destructiw- only for one year to crops following grass, and cultivated crops of subsequent years are untroubled until the land is laid down to grass once more. From the fact that the population of Leather Jackets is greatly determined by the kind of weather conditions in autumn, it is possible to forecast outbreaks of the pest. Wet weather in autumn is favourable to the Leather Jacket, with the result that it may be expected to be injurious the following spring. Rarely does an outbreak follow upon a dry autumn. Life-historg/.—The Leather J aeket deVelops from an egg laid by a Crane Fly, or Daddy Long Legs, an insect familiar to all. The two common grass-land Crane Flies are characterised by their dull greyish-brown colour, slender elongated bodies, g to 1 inch long, narrow parchment-like wings, and abnormally long legs, from which the flies earn their p0pular names. They are on the wing from the beginning of August till the end of September, and the period of their greatest numbers extends from 1st to 6th September. According to Barnes 2 the males live for one to fourteen days and the females up to ten days. The average number of eggs laid by each female is said to lie between 250 and 350, with a maximum of 487 and a minimum of 48. Pairing occurs soon after the files are born, and, according to Lovibond,3 the female lays practically her whole quota of eggs on the first day of her existence. The eggs are deposited at random on grass land when the Crane Fly is in flight over, or at rest among, the herbage, and they appear to be ejected with some force. Alternatively the female may bore a hole in the ground with its rigid ovipositor and deposit the eggs 1 Actually there are several different kinds of injurious Leather Jackets. Tipula paludosa and T. oleracea are the most common. 2 Barnes, H. F., 1937. “ Methods of Investigating the Bionomics of the Common Crane-Fly, Tipula paludosa Meigen, together with Some Results." Ann. App. Biol., Vol. XXIV., No. 2, pp. 356-368. ‘ 3 Lovibond, B., 1937. ” Investigations on the Control of Leather Jackets. (2) Notes on Craneflies and their Larvae.” Jour. Bd. Greenkeeping Res., Vol. V., No. 11, p. 12. INSECT AND OTHER PESTS OF 1939. 101 beneath the surface. Females of T. paludosa that were. kept by Lovibond 1 in glass tubes were found to deposit their eggs in clumps, while T. olcracca deposited only one or two at a time. On Scottish hill-farms Crane Flies are very abundant, and some idea of the degree of infestation of a Selkirkshire pasture was obtained from the egg counts of sod samples 9” x 9” X 6” extracted by the Ladell apparatus.2 This extraction, which was done in the winter months, had for its object an entirely different aim—namely, the dlscovery of hibernating individuals of the Sheep Tick. lnc1dentally, each sample examined yielded, among other soil insects, eggs Fig. 5.—I[atch€(l eggs of the Crane Fly, Tipula paludosa, recovered from i grassland. X 6. From nature. of Crane Flies which varied in amount from 10 to 100, .with an average of about 40, which is the equivalent of_an egg population of about 3 millions per acre. As our examinations were made during the winter, only empty egg-shells were found, together with a few that had failed to hatch (Fig. 5). 1 Lovibond, B., 1938. “Investigations on the Control of Leather Jackets. (3) Some Results of Breeding and Sampling Experlments during the Current Season.” Jour. Bd. Greenkeeping Res, Vol. V., No. 17, p. 1.04. 2 Ladell, W. R. S., 1936. “ A new Apparatus for separating Insects and other Arthropods from the Soil.” Ann. App. Biol., Vol. XXIII., p. 862 |
| Title | Transactions of RHASS Volume 1940 - Page 056 |
