affecting Carrots and Parsnips. 
179 
carrot crops, but of course the drier the weather is the better the 
lime will take effect.* 
The spirit of tar, however, has been so often successfully 
tried, and it is so applicable to field culture, that I shall give the 
best directions I am able to obtain for its use. Take a barrowful 
of sand and pour a gallon of spirits of tar upon it by degrees, so 
as thoroughly to incorporate the whole mass, with the hands, then 
sow it over the surface of the field intended for carrots. The 
above quantity will be enough for 60 or 70 square yards. The 
object of uniting the spirits of tar with the sand is to divide it so 
minutely that a small quantity may be scattered over a large 
space ; for it is believed that the scent is so offensive to insects, 
they cannot endure the soil where it is thus employed : under 
these circumstances the female flies would avoid such localities, 
and in all probability the spirits of tar would kill the young larvae 
if even they hatched. Some cultivators have applied this dressing 
in the autumn, digging it in and letting it remain until the car- 
rots were sown, whilst others have tried it after the sowing in 
April ; and I have heard of its being sown at the same time as 
the seed, with equally good effect. f When it is dug or ploughed 
in during the autumn, it is supposed to drive the vermm to the 
surface, where they perish ; and if repeated in the spring, after 
sowing, it no doubt renders the surface disagreeable to the flies, 
as I have already stated. 
In the cage where I bred the Psila I found also a species of 
Alysia, somewhat allied to the A. Ajni^X which I can only pre- 
sume was a parasite connected with its economy, as it might have 
been introduced with the soil. 
Millipedes and Centipedes. 
The Pobjdesmus complanatus is attracted to the roots which 
have been previously perforated by the maggots of the Psila, and 
sometimes congregates in such vast numbers, that I suppose it 
was this little animal which was reported to have devoured carrots 
by the acre in Scotland in 1831 ; but as its characters with figures 
have already been published in this Journal, it is unnecessary to 
give any further description of it here.§ It may, however, be 
added that these Millipedes are said to crawl about the surface 
beiore sunrise, when they have been collected into cans by 
myriads and destroyed. || A Centipede, named /S'cci/ope?2cZra elec- 
* ' Gardener's Mag.,' vol. xvi. p. 208. 
■|' ' Gardener's Chron.,' vol. ii. pp. 365, 726, and 821. Vol. iii. pp. 5 and 86. 
t Vide p. 192. 
§ Vide vol. v. p. 230, pi. J. f. 53. 
II 'Scotsman,' lorMay 14, 1831. 
N 2 
