FARMERS^ REGISTER— THE TURNIP FLY. 



219 



ration and extent. Their existence has given rise 

 to much speculation, and even tlie experienced 

 philosophy of JNIr. Jeticrson has succumbed to the 

 mystery* ol' their origin. 



Our frosts are souietimes equally severe and 

 unexpected; no body placed near the earth has a 

 temjjcrature oi its own, but is entirely regidated 

 by that of the earth. A violent storm of rain, by 

 absorbing much of the heat of the earlh, is oilen 

 followed by a destructive trost. When the jjower 

 of frost reaches a certain pitch, the vapors dis- 

 persed throughout the air, yield their latent heat — 

 the atmosphere becomes clouded, the ii-ost is either 

 destroyed or mitigated, and the vapors descend in 

 rain or snow. 



Our hardest frosts never penetrate the earth 

 more than three inches, and though the leaves of 

 the trees and shrubs are scathed or destroyed, 

 and tnnber somethnes splits in the direction of the 

 fibres of the tree, its roots unifbrml}^ remain un- 

 injured. Those portions of vegetation which grow 

 nearest to the earth, and those in low and marshy 

 situations, receive the severest injuries. On the 

 night of the 17tli May, 1834, the leaves of the 

 oak, hickory, and all the tbrest trees, were blighted 

 in most of their foliage; the s3-camore oidy re- 

 mained unhurt. Frost during the winter, is a 

 fatal enemy to those plants which are nurtured in 

 eouthern exposures; they are rarely covered with 

 snow, wliich melting rapidly, is converted in the 

 course of the night into destructive ice. Our lohite 

 frost is generally harmless, it being simple dew 

 slightly congealed. 



Dew is found in Virginia in heavy masses, gen- 

 erally in the months of August, September, and 

 October; it lies in greater quantuies on our flat 

 than high lands, being collected there during the 

 absence of the smi from the horizon, like the relics 

 of a drizzling rain; it appears first on the lower 

 parts of bodies, because in the evening the lower 

 atmosphere is first cooled and most disposed to 

 part with its vapor. 



Virginia is subject to rains of vehement and long 

 continuance; they fall in the largest quantity about 

 the breaking of the winter, and in INI arch and 

 September; I have no data on which to reckon 

 their depth t or their prevalence over the fair and 

 cloudy days of our climate. Our valley and west- 

 ern regions, by the condensing power of their 

 mountains, and our tide water sections, by the 

 attractive force of broad rivers, have more local 

 rains than the intermediate country, and do not 

 suft'er in the same proportion from continued 

 droughts. If a year be remarkable lor rain it is 

 fair to conclude that the ensuing winter will be 

 severe, from the great evaporation of the heat of 

 the earth, and if the rains have been violent, ste- 

 rility and baiTenness will follovv^ in the next year 



* May they not proceed from that latent elcctnciiy 

 which pervades the air most in dry seasons, and which 

 is attracted to the human body by its heat, — thus pro- 

 ducing from the action of affudiy, the feeling of sud- 

 den warmth ? 



t According to the observations of Dr. Sanders made 

 near Boston during ten years, from Januaiy 1, 1S21 to 

 January 1, 1831, there were on an average in each 

 year, 219 days of fair and 146 of cloudy weather. 

 Rain fell more or less on 57 days. Boston is on the 

 sea coast, in latitude 42 deg. 20—58 min. and the stand- 

 ard temperature of the level of the sea at that place is ' 

 .between 59 deg. and 60 deg. Farenheit. i 



in proportion, as the surface mould so vital to ve- 

 getation has been scattered and wasted away. 



Our Indian summer presents an ample field for 

 the creations of fancy and the conceits of theory'. 

 It generally follows excessive and protracted 

 droughts, and is dispersed by heavy rains. It has 

 been traced to electric influence — to the burning of 

 mountains — to the existence of numerous impal- 

 pable atoms of decayed vegetation, and has been 

 assimilated to those light gray clouds which over- 

 hang Peru. May Ave not ascribe it to that mass 

 of accumulated vapor which is precipitated on the 

 lower atmosphere, while the continued action of 

 the heat of the earth, and the rays of the sun con- 

 spire to produce the dense medium through which 

 the light is so irregularly refracted ? 



But I must conclude my tedious communication 

 or I shall incontinently vex you with the idle spec- 

 ulations of delusive theory, which in seducing from 

 the path of truth, ever persuades us that its fond 

 dreams are facts, and its forced assumptions, fixed 

 principles. 



\V. G. M. 



0:V THE ORIGI3V OF THE TURNIP FLY, AND 

 BIEANS TO PREVENT ITS RAVAGES. 



From the Entomological Magazine. 



The turnip fly is not always of one kind, but 

 the dilTerence in them is not ver}^ important; for 

 they only alter in their paint, their build is always 

 ahke. The most common is bottle-green, but in 

 some fields all are painted black, Avitli a white line 

 on each side from stem to stern down the neck. 

 They are so active, that the only way in which I 

 could ever obtain them in newly sown fields, was 

 by sweeping the surface with a gauze net, on an 

 iron hoop at the end of a strongish stick. They 

 jump like fleas as soon as they see you. This in- 

 sect, or rather its grub, commences its attack on 

 the turnip as soon as it is up, devouring the two 

 cotyledons and the little heart, and sometimes in a 

 (e_\v days leaving the field as brown as it was on 

 the day it was sown. Schemes without number 

 have been tried to get rid of or kill this little pest 

 wherever it has appeared. I have always ob- 

 served the greatest quantity of grubs on verj' young 

 plants; they are very various in size, and it is not 

 before the plants are a fortnight or three weeks 

 old, that the beetles appear in any quantities. Yet 

 there are some beetles observed at the first coming 

 up of the plants. Now I know from experience, 

 that the turnip-fly feeds on wild mustard, and se- 

 veral other hedge plants, and therefore it is not 

 improbable, that when they smell the fragrance of 

 the fresh bursting cotyledons of their favorite food, 

 they would skip down from their spring habita- 

 tions, the hedges, and make the attack. I first 

 sowed some seed in a flower-pot, with earth out 

 of my garden; it produced the animal in abund- 

 ance. Secondly, I enclosed the pot with paste- 

 board and canvass, with the same success; but still 

 there was a possibility of the enemy getting in, as 

 I had not the cover sufficiently close. Thirdly, I 

 made a light frame about eight inches square, co- 

 vered it whh very fine silk gauze, carefully stop- 

 ping the crevices of the door with pasted paper, 

 and round the pot where the cover was fastened 

 on with putty, so that there was no possibility of 

 any thing coming to it from without. Yet this 

 experiment was attended with the same success; 



