54 



SCIENCE-GOSSIP. 



[March 1, 1866. 



ON SOME PESTS AND THEIR CHECKS. 



npiIERE is a subtle relation between the health 

 -"- of plants and the attacks they suffer from 

 insects. One may watch an apparently healthy, 

 vigorous shoot on a favourite rose-bush and expect 

 it to be presently crowned with roses. Has a current 

 of cold ah* breathed unkindly upon it? Has an 

 Aphis in its perfectly-developed winged state halted 

 there a moment, and unseen deposited some eggs ? 



Qiden sabe (who knows) ? — but there comes first 

 an uncomfortable roughness, as if the plant were per- 

 spiring through the pores of its epidermis. These 

 small beads of moisture soon show themselves to be 

 living six-legged creatures, with bodies of bright 

 green jelly, and they grow and increase, both in size 

 and numbers, with the most marvellous rapidity, till 

 they jostle and tumble over each other, coating the 

 stem and leaves with their bodies, as thickly piled 

 together as a swarm of bees round the branch where 

 their queen has settled. Alas ! poor plant, how your 

 life-juices will now be sucked and drained ! But 

 help is at hand when least expected. Gardeners in 

 general do not like ants : they accuse them of disturb- 

 ing the soil from the roots of plants, and of various 

 mischief. Yet now they come as allies to help the 

 beleaguered fortress. In serried file they issue from 

 their citadel, march in straight line across gravel- 

 paths or smooth-raked border, climb up the stem, 

 and quickly settle themselves where the Aphides 

 are thickest and busiest, and greedily drink the 

 honey-dew which they excrete. There have been 

 various meanings given to the oft-quoted remark of 

 M. P. Huber, the younger, that " the plant-lice serve 

 instead of cows and goats to the ants " — pastured 

 through the winter they could not be ; and Gould, 

 Latreille, and others have found that the ants be- 

 come dormant, and do not require stored-up food for 

 that time. In this little episode of the raid of the 

 emmets on the rose-bush, there could be no such 

 commissariat-providing prevision as that by which 

 the respectable Dr. Watts would have us think 

 " they foresee all the frosts and the storms, and so 

 bring their food within doors ; " on the contrary, 

 judging by the dried, empty skins, and the altogether 

 defeated and discomfited state of the Aphides, one 

 may suspect that the ants, God Bacchus - like, 

 mounted on and tapped their barrels of liquor, and 

 gorged themselves with the sweet inebriating juice 

 fresh from the heart of the distillery, till heavy and 

 stupefied, the ants roll helplessly on the stem, and 

 possibly, by the formic acid exuding from them, 

 might do more harm to the plant than their soft 

 green predecessors. But help comes again : amongst 

 the dark mass of the now lazy ants, move some red 

 coral beads prettily speckled with black ; these are 

 Coccinelhr, equally greedy after the Aphides and the 

 honey-dew, they soon dislodge those who would 



debar them from their feast, and the ants helplessly 

 tumble about and nearly disappear, as the Aphides 

 had done before. Ah, then, " lady-birds, lady-birds, 

 fly away home," stretch out your pretty gauze 

 winglets— begone ; shelter yourselves in the dahlias 

 or under the broad sycamore leaves, and lick up 

 what remnants of honey-dew you can find, for here 

 come numerous feathered fiutterers to pick you up 

 like grains of wheat. Your friends the hop-growers 

 will willingly help to hide and protect you for the 

 sake of the great services you render them against 

 the Hop-aphis. In confirmation of my suspicions 

 against the sobriety of the ants, Dr. J. E. Gray has 

 just written to me, "I know that ants do get 

 drunk." They pass up the stem of the laurel, the 

 broad-leaved evergreen (Primus Laitrus-cerasiis), 

 drink the secretion from the gland on the petiole, 

 and get so mugged they cannot find their way 

 down again, and some seem to die on the spot. 



Dr. Kirk told me he caught the Galagos (a small 

 Lemur) when they had been up in the palm-trees 

 drinking the juice which the negroes brew into palm- 

 wine, and they would come staggering into the house, 

 and were easily caught. On mentioning this to a 

 friend, a distiller, he told me he had a Skye terrier 

 given to him which got the habit of going to the end 

 of the worm and sipping the spirit as it dropped out, 

 and got so intoxicated it could not walk, and nothing 

 could cure it, so it was obliged to be sent away where 

 spirits were not made. The Aphides we have spoken 

 of have soft green luscious-looking bodies, which 

 offer an easy and tempting prey to their enemies ; 

 others have curious means of defence. Eor instance, 

 the little green insect which involves itself in a wet 

 frothy spume, and either from its making its appear- 

 ance when the cuckoo calls, or because it is more 

 frequently found on the cuckoo-flowers (Cardamine 

 pratensis) than on any other plant, has the popular 

 name of Cuckoo-spit. 



The Aphis lanigera, commonly called American 

 blight, which so deforms our apple-trees with great 

 white scabs, is rolled in webs of cotton-wool, which 

 not only preserve the inclosed insects, but serve 

 them as flying chariots; small flakes of the web being 

 wafted by the wind from tree to tree spread the 

 pest. If you take hold of these flakes, your fingers 

 become bloody with the insects, whose covering you 

 thus crush. This sort was particularly abundant in 

 this last hot, dry summer; but after the heavy 

 autumn rains the apple-trees appeared to be washed 

 quite clean, and the woolly patches had disappeared. 

 On searching closely in November, however, I fouud 

 in cracks, in the axils of branches here and there, a 

 very small soft grub inclosed in a smooth silky 

 cocoon, which, I think, was the chrysalis state of the 

 perfect Aphis ; and which, in spring, would produce 

 the wool-spinning stage of the Aphis. In the cocoon 

 state, however, they are accessible to the bills of 

 such small birds as may be industrious enough to 



