1066 



PRACTICE OF AGRICULTURE 



Part III. 



6861. All the gratiivorous birds are injurious to the farmer at seed time and harvest, and 

 must be deterred by watching or shooting, by scare-crows, as figures of men, cats, &c. , 

 by rags dipped in bruised gunpowder and tar, renewed every day or two ; but chiefly 

 by shooting and fixing up the victims in different places. It must always be recollected 

 that birds are, with very few exceptions, insectivorous as well as granivorous, and that 

 frequently they may do much good in destroying the grub and wire worm. This is 

 more especially the case with the crow tribe, {Corvus, L,) (See Encyc. of Gard. 2223.) 



Sect. III. Insects injurious in Agriculture. 



6862. The insect tribes are by far the most dangerous animals that the agriculturist 

 has to contend with ; and injurious as they are in Britain, their destructive effects are 

 here but trifling compared to what is experienced from the locust in eastern countries, 

 and various insects in North America. Dr. Dwight, in his Travels in New England, re- 

 lates accounts of the Hessian fly ( Tipula), destroying the crops of entire districts, and 

 rendering it impossible to cultivate a particular variety of wheat. It made its first ap- 

 pearance in New England in 1787, and advanced at the rate of 20 miles a year. A ca- 

 terpillar called the palmer worm appeared in 1 770. Its march was from west to east ; 

 walls and fences were no obstruction to its course, nor indeed was any thing else, except 

 the sides of trenches. It destroyed, rather than devoured, ascending a stalk of grass, or 

 grain, cutting it off in a moment, and, without staying to eat any part of it, rapidly re- 

 peating the same process on all which stood its way. The meadows, where it most 

 abounded, appeared as if they had been mown with a dull scythe ; and the grain, as if it 

 had been reaped with a sickle which had gaps, and therefore had cut the stalks in a 

 scattering, slovenly manner. In some places, immense multitudes of these animals died 

 in the trenches, which were formed to stop their progress, and were left uncovered. The 

 mass soon became foetid and loathsome ; and was supposed in several instances, to produce 

 a fever distressing, and sometimes fatal. The canker worm, another caterpillar, lives on 

 apple-trees, and entirely strips them of their, leaves in the course of four u-eeks. A sort 

 of grasshopper appears occasionally in vast numbers, and not only eats every thing of 

 the vegetable kind, but even " the garments of labourers hung up in the field while 

 they are at work, which they destroy in a few hours." (Dwight^s Travels, vol. ii. 

 p. 384. ) Every species of larger animal and plant seems to have a particular species 

 of insect which it is destined to support, and to which it will fall a victim unless in vigo- 

 rous health ; and in the case of animals, notonly in good health, but in the habit of using 

 the means which nature or art suggests for their suppression or destruction. We shall 

 first offer some general remarks on the nature of insects, and next describe a few belong- 

 ing to each of the Linnaean orders. 



SuBSECT. 1 . Of the Physiology of the Insect Tribes. 



6863. Insects are distinguished from quadrupeds, birds, and reptiles by their more 

 numerous feet, being without bones, and by their head being furnisfied with a pair of 

 antenna; or horns. From the vermes, or worm-like animals, insects are sufficiently dis- 

 tinguished by their having feet. 



6864. Taking a general view of insects we find most of them are oviparous ; of course 

 the first state in which insects appear is that of an ovum or egg. This relates to the 

 generality of insects, for there are some examples of viviparous insects, as in the general 

 aphis, musca, &c. The eggs of insects (fg. 748 ) 748 



are of two sorts : the first membranaceous, like the 

 eggs of the tortoise, and the other reptiles ; the other 

 covered with a shell like those of the birds. Their 

 figure varies exceedingly ; some are round, some 

 elliptical, some lenticular, some cylindrical, some 

 pyramidal, some flat, some square, but the round 

 and oval are the most common. As an example of 

 the various shapes of the eggs of insects, and of 

 their natural as well as magnified size, we refer to 

 those of the common slu^ (a), phalaena nupta {b], 

 brown-tailed moth (c), currant moth (rf), common 

 gooseberry moth (e;, turnip butterfly (f ), spider (g), 

 house cricket {h], and common chafer (i). 



6865. The egs of insects seldom increase in size, from the time they have been deposited 

 by the parent, till they are hatched ; those of the tenthredo, however, and of some others, 

 are observed to increase in bulk. At first there is nothing to be perceived in the eggs 

 of insects but a watery fluid; after some little time, the head, like an obscure point, is 

 observable in the centre. The little insect remains in the egg till its limbs have acquired 

 strength to break the egg and make its escape ; the different species of insects remain 

 enclosed in the egg for very different periods ; some continue enclosed only a few days, 



