Book VII. NOXIOUS INSECTS. 1115 



fall through the nostrils, and change to the chrysalis (h), which produces the fly (g) in about two monthj. 

 Swine, pigeons, and all kinds of poultry are subject to fleas, and lice of various kinds, but never to such 

 a degree as to occasion death. 



7659. Fish, in their young or fry state, are the food of the larvae of water beetles (Dytisci). These 

 insects are frequently seen in great numbers in ponds : they may be caught by a hand net (made of 

 very small meshes), inserted beneath the insect, as he reposes (with his head doAvnwards) on the surface, 

 and then suddenly drawn upwards. 



SuBSECT. 4. Insects injurious to Vegetables. 



7660. The ravages of insects upon plants commence from the time that the seed is committed to the 

 ground, and continue until the produce is gathered into the barn. These various injuries, in one shape 

 or other, are annually experienced ; and many of them, beyond all doubt, will hereafter increase to an 

 alarming extent, if the great body of agriculturists persevere in their mistaken prejudice against crows, 

 rooks, and other useful birds, which Providence has kindly given us, to keep the insect tribes within due 

 limits. We have already noticed the destructive insects which are in a great degree peculiar to certain 

 plants, as wheat, barley, &c. in ageneral way (Part III. Book VI.) : we shall now enumerate those that 

 infest the grains, clover, pastures, cabbages, and fruits, plantations, as well as those universal destroyers 

 of all vegetables, the wire-worm, the plant lice, and the different species of crane-fly. 



7661. Wheat, in every state, is subject to many insect depredators. Mr. Marsham describes a small grub 

 (by some mistaken for the wire-worm), which eats into the young plant about an inch below its surface, 

 devours the central part, and thus causes its immediate death. Out of fifty acres sown with wheat in 

 1802, ten had been destroyed in this way so early as October. At a later period this grain is attacked by 

 a fly nearly related (according to Mr. Kirby) to the Mosfllus arcu^tus of Latreille. It makes a lodgement 

 in the heart of the principal stem just above the root, which stem it invariably destroys, giving the crop 

 at first a most unpromising appearance ; but it proved ultimately that the plant, instead of being injured, 

 derived great benefit from this circumstance; for, the main stem perishing, the root (which was 

 not hurt) threw out fresh shoots on every side, so as to yield a more abundant crop than in other fields 

 where the insect had not been. When first observed in England, this insect caused great alarm among 

 agriculturists, who thought it might prove the Hessian fly. When the wheat blossoms, it becomes ex- 

 posed to the attack of a small orange- coloured gnat, which deposits its eggs in the centre of the flower j 

 the larva or grub devours the pollen, and thus prevents the impregnation of the grain. The weevil, a 

 small coleopterous insect {Caldndra granaria F.), is extremely destructive to wheat when in the granary, 

 where it feeds both in the larva and perfect state : against the first, we are acquainted with no remedy, 

 as it lives in the grain ; but as this is larger than the perfect beetle, the latter may be in a great measure 

 collected by means of a sieve, large enough for the insect (but not the grain) to pass through : it is often 

 found in such numbers, that they have been collected and destroyed by bushels. The same insect, or one 

 very near it, often infests sea biscuit ; and can only be killed by baking or heating the biscuits over again 

 in an oven. 



7662. Itye is subject to the attacks of a small fly (Musca pumilionis), which introduces its eggs into the 

 heart of the shoots, and occasions a loss of from eight to fourteen plants in a square of two feet. No remedy 

 has yet been proposed for this pest, which, if not extensive, may be checked by plucking the injured ears, 

 and burning them. 



7663. Barley, besides other insect foes, has one peculiar to itself, in the shape of a small moth (TYnea 

 h6rdei K). This fly deposits from twenty to thirty eggs on a single grain ; when hatched, each of the larvEB 

 disperses, and selecting a grain for itself, enters from without, and lies totally concealed : should these 

 moths be observed in a granary, the injury may be stopped by carefully covering the grain, leaving a few 

 handfuls exposed ; upon these the moths will deposit their eggs, and by roasting or destroying this small 

 quantity, the rest may be saved from infection. 



7664. Oats are subject to few diseases ; but, like all other grain, the plants are liable to be destroyed by 

 that universal devastator the wire-worm, of which a more particular account will be found in treating of 

 insects universally injurious to vegetables. 



7665. The diseases of peas are mildew and blight, but these are only occasional ; its insect enemies, 

 however, are formidable. The principal of these is the plant louse (A^phis), one species of which is pecu- 

 liar to this plant. In the year 1810, the crops of peas throughout the whole kingdom v/as so much 

 destroyed by it, that the produce was not more than the quantity sown ; and many farmers turned their 

 swine into their pea-fields, not thinking them worth ga^^her-ng. [Kirby and Spence, i. p. 177.) Beans are 

 exposed to the same injury from another species of A^'phis of a black colour, which begins at the top of the 

 plant, and multiplies downwards. In both cases the most effectual remedy is to top the plants at an early 

 period of the infection, an<l burn the parts so gathered ; this plan is likewise advantageous, as it improves 

 both the quality and quantity of the crop. The earlier peas are sown, the better chance they stand of 

 escaping this pest; or if a small quantity of quick-lime is sprinkled upon them when they are a few 

 inches high, experience has shown that the plants remain uninjured, while the A'^phis is totally de- 

 stroyed. 



7666. The diseases of beans are the rust, honey-dew, and mildew. The insects which infest it, and their 

 eradication, have already been noticed. (5256.) 



7667. jTwrm);* are subject to several peculiar diseases, and are the food of many noxious insects. On 

 the first appearance of the cotyledon leaves, a whole host of little jumping beetles (Haltica n^morum), 

 called by farmers the fly and blackjack, attack and devour them, so that the land is often obliged to be 

 resown. An eminent agriculturist has calculated, that from this cause alone the loss sustained in the 

 turnip crops of Devonshire in 1786 was not less than 100,000/. {Young's Annals, vii. p. 102.) Nearly as 

 much damage is sometimes cau.sed by a little weevil (CurcWio contractus Marsham), which in the same 

 manner pierces a hole in the cuticle j watering with lime water, &c. may serve to check both these 

 evils. 



7668. The caterpillar of a saw-fly (Tenthredo I..'), entirely sure, ^e enticed ard destroyed, like the true "wire-worm, -which 

 of a black colour, appears on the plants so soon as they have also does extensive injury to turnips. The small knob or tu- 

 produced three or four rough leaves: these have sometimes bercle, often observed on the roots, is inhabited by another 

 occasioned considerable mischief, particularly in 178.'5, when kind of grub, probably the larva either of Curcilio contrac- 

 many thousand acres were, on this account, ploughed up. tus M., or RynchseSius assfmilis F., two small weevils. These, 

 These caterpillars are sought after with so much avidity by however, do not seem to aflect the growth of the plant, 

 crows, rooks, and magpies, that those farmers, whose good 7670. The vegetable lUteasei of the turnip are the mildew (by 

 sense have led them not to destroy, but rather to encourige, some considered the effect of insects), dLstortion of the root 

 these useful birds, need not fear any great damage from this (known prjncipallv by thenameof fingers and toes), the anbury, 

 insect. To destroy it in the most efiectual way, watering or the canker, and gangrene, or wasting from water EUid frost, 

 sprinkling with lime has be^n strongly recommended. None of these injurious diseases, as far as is known, admit 



7669. The caterpillar of the turnip Iniiterjly (Pier;* nkpffi F.) either of prevention or cure : under favourable circumstances 

 is also sometimes found on the turnip in great numbers : nearly of soil, culture, climate, and weather, they seldom occur; and 

 fifty of the grub, which so much resembles the wire-worm, and therefore all that the cultivator can do is to prepare and manure 

 which we have before alluded to (766.), have been found just his land properly, and in the .sowing season supply water when 

 below the leaves of a single bulb. These may, in a great mea- tJie weather is dry. 



7671. The hop is liable to many external and internal diseases : by the first term we must be understood 

 as alluding to mjuries caused by insects, while those which belong to the vegetable are certainly internal. 

 When the plants first emerge above the ground, they are infested by a small beetle, vulgarly called the 

 flea. In a more advanced state the tops and branches are devoured by the hop A^his, known to some by 

 the name of the green fly, while at the same period the rrets are 'ubj'^t to the attack of the caterpillar 



