76 



The Natuealist. 



to be mainly depended upon as an agent for tins purpose is desiccation, — 

 that is, drying the egg by throwing it out. from its natural locality to such 

 influences of air and sunshine as may dry up the contained fluid, and 

 thus prevent the embryo within from developing. It is possible to 

 prevent attack by turning the eggs down to an ascertained depth, at 

 which, although the tenant may hatch out, yet if the ground is in a 

 natural state the insect cannot penetrate it. If the earth is cracked, of 

 course the deep crevices admit air, and alter the state of the case, but it 

 is plain that we can destroy great numbers of eggs by throwing them out, 

 upwards or downwards, from their natural place of deposit, and also we 

 may diminish the quantity of eggs laid above ground by decreasing the 

 number of places proper for egg-laying. Clearing away neglected weeds 

 will demolish many nurseries of coming attack, good limiug will keep the 

 click beetle from laying eggs to infest the meadow with wireworm, or a 

 better plan is penning sheep on grass that it is particularly desirable to 

 protect, thus not only preventing oviposition, but destroying the young 

 grubs just beneath the ground from its being sodden with matter injurious 

 to insect life. The use of chemical manure, such as super-phosphate, has 

 been found to decrease the ravages of the cabbage-root maggot ; while, 

 as the onion-flies lay their eggs very frequently either just below the 

 surface of the ground, or if possible at the base of the bulb, it has been 

 found that if onion bulbs are earthed up from time to time the flies are 

 thus obliged to lay their eggs at haphazard, on the leaves or ground, or at 

 least not in such a position that the maggots, if they hatch at all, can 

 make their way to their food, and this prevents very much of the attack, 

 and agrees well with the plant-growth. Passing to deal with larvae, the 

 lecturer pointed out that in this country the conditions which are most 

 favourable for the hatching of the larvse of the greater part of our insects 

 are moderate warmth, together with some degree of moisture, while heavy 

 rain, and especially rain following a term of warm dry weather, is most 

 destructive to larvae exposed to it, as well by its immediate effect upon 

 them as presenting them food caused thereby to be unsuitable to larval 

 life. The turnip fly, or beet fly, or whichever it may be, was very 

 injurious till the rain washed it off, or started the plant, or in some way 

 put an end to its ravages ; and it was pointed out that when we look at 

 the injury caused by overplus of rain in some years and deflciency in 

 others, and the benefits that might possibly be derived from a more 

 extended plan of field cisterns, it is so plain that a better regulated 

 distribution of water, both as an external application to clear off insect » 

 vermin and for absorption by the roots to press on the growth, would be 

 thoroughly useful, that the point of how far it could be managed by steam 

 power at a paying rate is well worth thinking of. Miss Ormerod con- 

 cluded : The coolness and darkness of the night, or the bright sunshine, 

 as distinguished from the cloudy light of mary of our summer days, aU 

 have their effect on insect life, some of which we can utilise, and some of 

 which, although we cannot alter them, will benefit us, if we notice them, 



