3G0 



THE FARMER'S MAGAZINE. 



devoured but the midrib fibres, and the entire crop is 

 destroyed. There are at least two broods of these in- 

 sects in the year. The eggs that are first deposited, 

 passquickly through the stages of larvae, and nymphse, or 

 papse, and become perfect flies in July or August, when 

 these also deposit their eggs, and with the same destruc- 

 tive results. The writer has seen a field of turnips thus 

 completely destroyed by them, when the bulbs had 

 attained a considerable size, and the ground was covered 

 with the foliage. They sometimes appear as late as Oc- 

 tober; but it is only when that month is unusually warm, 

 that they can effect much mischief, as the cold frosty 

 nights enfeeble, if they do not wholly destroy them. 



The larva changes its skin three times, at intervals 

 of from five to seven days. After the last change, it 

 attains its full maturity, and is then about an inch in 

 length, and becomes doubly destructive, especially if 

 the weather be bright and hot, which is particularly 

 grateful to it. It is probable, however, that but few of 

 the October brood have sufficient strength to go through 

 the labour of preparing to enter the pupa or chrysalis 

 state. 



As soon as the larva has attained its full growth, it 

 burrows into the ground to the depth of some inches, 

 where it undergoes its next change, and becomes a chry- 

 salis. "With the first brood these changes are very 

 quickly gone through, and a fresh progeny is produced. 

 But the later broods, having entered the earth, form an 

 oval cavity or cell, in which they remain until the fol- 

 lowing spring ; still in the form of larvse ; not changing 

 into the chrysalis state until about the latter end of 

 April or beginning of May, and soon after assuming 

 the form of the perfect fly. In the earth they form for 

 themselves cocoons like all of the caterpillar tribe; 

 these are about half an inch in length and a quarter of 

 an inch in diameter, and in them the insect passes the 

 winter in perfect security from the cold and wet, neither 

 of which appears to injure it after it has completed its 

 defence. A cold and wet spring and summer, however, 

 retard, and probably prevent for the time, the deve- 

 lopment of those changes it undergoes, or rather 

 should undergo at that period. And it is thus that we 

 may account for its non-appearance in such seasons. 



It has been ascertained that the charlock {Sinapis 

 arvensis) is the most natural food of this insect ; and 

 that when this wild plant abounds, it will devour it first 

 before attacking the turnips. The charlock is of the 

 same family of plants with the mustard ; and the pre- 

 dilection of the insect for that plant, pungent as its 

 leaves are, is a singular fact in its history. It would be 

 well if it confined its voracity to it; but it is far from 

 being thus satisfied. It will make clean work of a field 

 of turnips in an incredibly short period, devouring the 

 entire cellular tissue, and leaving only the mid-rib and 

 its fibrous branches ; never leaving a plant whilst a par- 

 ticle of the softer portion of the leaf remains. We 

 have never known a field of turnips recover from the 

 injury, so as to be of the smallest use to the farmer ; 

 and when the caterpillar has done its work, the best plan 

 is to plough up the ground at once, and prepare it for 

 some other crop. 



With regard to the means of preventing the mischief, 

 we have heard of none hitherto, in which we place any 

 confidence. It is only in the larva state that it can do 

 mischief; but in that state it appears to bid defiance to 

 the malice of its foes. Unslacked lime, wood ashes, 

 salt, a rope dragged over the plants, &c., &c., have all 

 in turn been tried without effecting a cure. Some have 

 undoubtedly been destroyed by all these means, but 

 " their name is legion,'' and fresh armies of them fill 

 up the ranks of those destroyed. The most effectual 

 plan hitherto adopted is that of turning ducks into 

 the field. These birds are excessively fond of the 

 black palmer, and will devour immense quantities of 

 them. But a moderate-sized field of turnips would 

 require an army of ducks in the proportion of at least 

 fifty to the acre, to produce any sensible impression 

 upon the enemy. Few persons have any idea of the 

 vast numbers of the insect tribes that infest the crops. 

 A friend of mine, many years ago, invented a plan for 

 taking the green flies (aphides) off a field of beans in- 

 fested with them. Two men worked the machine over 

 a field of about eight aci'es, and took off twelve bushels 

 of the aphides, which our friend presented to his pigs, 

 who gratefully accepted and duly appreciated the gift. 

 The "palmer" is probably less numerous, but a hun- 

 dred times bigger, than the aphis ; and how any rea- 

 sonable stock of ducks on a farm could save a crop of 

 eight or more acres of turnips, we are at a loss to con- 

 ceive. It is found, too, that the food disagrees with 

 the ducks ; and it is not an improbable result that, 

 without saving his turnips, a farmer would run the 

 chance of losing his ducks also. Mr. Newport recom- 

 mends that, when the yellow fly has made its appear- 

 ance on the turnips, the whole field should be watered 

 with sea-water or a solution of salt in water twice a 

 day, in order to prevent the hatching of the eggs. This 

 plan would be more practicable now than formerly, by 

 means of the apparatus for distributing liquid manure ; 

 but still, it would be attended with some considerable 

 trouble. All saline liquids are destructive to the insect 

 tribes, especially those with soft skins, as the various 

 kinds of larvae ; whilst the application of the moisture 

 would in the first instance retard, if not wholly prevent, 

 the hatching of the eggs. We are not by any means 

 assured that the plan our friend adopted to save his 

 beans, would not be effectual to take the palmer off the 

 turnips. He used a light bag, about six feet long, each 

 edge of which was nailed to a lath of the same length. 

 This was drawn over the tops of the turnips ; and the 

 flies fell into it, and were removed from time to time 

 into a cask. The difficulty with the palmer would be 

 in preventing them from walking out of the bag. But 

 if some caustic substance — quick-lime or wood -ashes, 

 for instance — were kept in the bag, it would at once 

 destroy the larvse. At any rate, the plan is worth a 

 trial, as it would be attended with very little trouble, 

 and less expense ; and the saving of a turnip crop is no 

 light matter to a farmer. C. 



N.B.— For. a more detailed account of the tenthredo, we 

 refer the reader to Marshall's Minutes of Norfolk Agriculture. 



