On Deep Draining. 
493 
holes in a straight line at equal distances across the land, then to 
place in these holes pegs, of which the tops should all be on a 
level : this should be done previously to cutting an experimental 
drain, of which the depth might be gradually increased, and the 
effect would be shown by the sinking of the water in the different 
holes. The best time for obsenation is when heavy rains are 
followed by fine weather, leaving the level undisturbed ; corre- 
sponding observations should also be made in a similar soil not 
subjected to the action of drains, that the two may be compared. 
In the clay soil, where most of my obsenations have been made, 
after the summer of 1S44, which was unusually dry, no more than 
4 inches of rain, falling within 30 days, saturated the soil, though 
the drains cut in the previous winter ran before any water could 
be traced as stagnating in the soil — a fact worth notice, and I 
think to be easily accounted for by the extent to which the ground 
was cracked, by which the water, falling in heavy showers, ran 
at once down these channels into the drains. A few simple 
observations, made as I have attempted to describe those made 
by myself, would I think satisfy any one within 48 hours that 
deep drains must be more effective than shallow, the former 
scarcely draining the tilth, the latter the subsoil. 
XLI. — Observations on the Natural History and Economy oj 
various Insects, ^-c, affecting the Corn-crops, including the para- 
sitic Enemies of the fFheat-midge, the Tfirips, Ulieat-louse, 
Wheat-buy, and also of the little icorm called Vibrio. By John 
Curtis, F.L.S., Corresponding Member of the Imperial and 
Royal Georgofili Society of Florence ; of the Academy of 
Natural Sciences of Philadelphia; &c. 
Paper X. 
Cecidomyia Tritici — The British Wheat-midge. 
I HAD hoped, during the past summer, to make some progress in 
the furtlier development of the economy of the Wheat-midge ; but 
although the little orange larvae were abundant in some wheat- 
fields in August in this neighbourhood, owins to the wet and cold 
season 1 presume, I did not discover a single midge on the wmg, 
and the larvae appear to have all died as usual. I have, however, 
collected materials for detailing the histories of sevei-al minute 
IchneumonidcB that attack the Wheat-mid o-e, which are too 
mterestmg and important to be passed by without comment. 
The most abundant and, consequently, the most useful of them is 
2 l2 
