76 THE DICTIONARY 
OF GARDENING, 
Tremex—continued. 
to the wood of Pear-trees, and also to Elms and Maples, 
in Canada and the United States, and may not impro- 
bably be introduced into Britain in trees from those 
countries. The female has the body about 1l}in. long, 
with the ovipositor extending nearly şin. backwards. 
The wings have a spread of about 2tin.; they are 
smoky-brown. The head and thorax are reddish-brown, 
with black markings; and the abdomen is black, with 
seven yellow cross-bars, each, except the first two, broken 
in the middle. The male is little more than half as 
large as the female, and the markings are less con- 
Trenching—continued. 
one end, and wheeled to the opposite end, where it is 
intended to finish. The depth which should be taken 
out varies according to the nature of the subsoil; if this 
is unfit to bring to the surface, it should be dug 
and still left beneath. Another width should then be 
marked ont, and the top spit of soil turned over to 
take the place of that wheeled away, the bottom being, 
in its turn, treated like the first; and so on. When the 
soil is good enough to allow of the bottom spit being 
brought to take the place of the top, the first trench 
must be taken out to the full depth, and the bottom 
a Fig. 91, TREVESIA EMINENS 
spicuous, the body being reddish, varied with black, 
and the wings more transparent. 
Should this insect be dovidontally ‘imported, the 
measures to be employed against it are the same as 
those recommended under Sirex. 
TRENCHING. A term applied to the process of 
a igging ground for the special purpose of increasing its 
4 Sepik i for the better cultivation of various crops. It is 
ch in autumn, and the surface thrown up 
the weather. In commencing | 
the soil, for about the wile a 
broken up. Trenching invariably deepens and improves 
garden land, but it is not always advisable to bring up 
the bottom soil at first; this is sometimes of a nature 
which causes actual harm to crops, and had better be 
left at the bottom below the limit which the roots reach. 
Trenching must, therefore, be practised with judgment. 
The bottom soil may always be loosened and dug, with 
advantage to that on the surface ; and if some loose leaf 
mould.or light manure is mixed into that beneath during 
the p ss, it will, in course of time, improve the whole 
and render it of a better description than before 
Bs è much greater depth. 
