PREVENTION AND DESTKUCTION OF INSECT PESTS, 513 



stniction, which is one of the most important features in prevention, 

 let us see where insects generally take up their winter quarters. 

 After an attack of onion maggot, rust, celery fly, cabbage maggots, 

 and wurzel fly, &o. (all of which are the larvae of Diptera), we shall 

 find in the ground during the winter numberless small, oval, brown 

 bodies known as " puparia," each of which contains a pupa derived 

 from one of the maggots. We must not forget, however, that some 

 of the larvae have not matured by the time the crop was lifted, and 

 thus some are harvested with the crop, as we find in maggoty 

 onions and rusty carrots ; or they may remain in the leaves, as in 

 the case of celery-fly, or in the rotting stalks and roots, as in cabbage 

 maggots. Now, if these are left in and on the ground and not 

 destroyed, fresh generations appear next year, and should a similar 

 crop be grown on or near the same land it stands a considerable 

 risk of further attack. Again, in sawjly larvce attack on fruit-trees, 

 at the end of the year the larvse fall to the ground, bury themselves 

 a few inches beneath the bushes and trees, and forming a case of 

 silk and earth, likewise later pupate. They often remain as larvae 

 in the cocoon until the spring, and then pupate. A very large 

 number of moths also are found in the pupal stage in the earth 

 in the winter time. At this time of year one and all should be 

 destroyed. Two methods seem to recommend themselves — one, 

 turning over the land so as to expose the pupsB to the attack of 

 birds, which greedily devour them ; another, by deep trenching the 

 land so as to bury the insects. After a bad attack of currant saw- 

 fly, we may remove the soil from beneath the currant and gooseberry 

 bushes in winter and burn it in gardens. 



It must he rememhered that frost has little or no injurious effect 

 upon insects in the egg or pupal state, or even upon most maggots. — 

 I have known chrysalids frozen as brittle as glass, and yet their 

 vitality was unimpaired. Frost, if anything, is beneficial to insect 

 life, for the hard state of the ground protects the creatures from the 

 attack of birds. Many insects hibernate in the adult state, — such 

 as the turnip- flea, thrips, apple-blossom weevil, earwigs, &c., — taking 

 refuge in hedgerows, grassy headlands, rubbish-heaps, under dead 

 bark, and so forth. Hedges bordering fields and gardens, and all 

 grassy patches, should be well cleaned in the winter, the material 

 burnt, and all rubbish cleared off' and similarly destroyed. The dead 

 leaves that collect in currant-bushes harbour the young larvte of the 

 currant moth {Abraxas grossulariata), and should therefore be 

 cleaned out. All prunings of fruit-trees should he hicrnt, and not 



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