190 
P. M. CAMPBELL-THE HESSIAN ELY. 
pest reached us. We can he confident that, from wherever we 
imported the puparia, some of them were tenanted by parasites. 
I have no doubt, however, that although there is uniformity in 
most parasites as to the selection of their hosts, there are indi¬ 
genous species of the Chalcid genera sufficiently polyphagic to infest 
any foreign insect, such as the Hessian fly, which may effect a 
lodgment in our country. I cannot identify any of the parasites I 
have reared from the puparia with the Bussian or American species. 
Precautionary Measures. 
In America considerable importance is advisedly attached to the 
late sowing of wheat, so that it should not he above the ground 
when the Hessian flies reach maturity in autumn. In our country 
the seed time is such as to preclude any chance of the crop being 
attacked before spring. There are, however, other methods re¬ 
commended in America which are not always practicable in this 
country. If for instance the stubble were left long it could he 
burned, and the hybernating puparia would he destroyed—hut this 
for obvious reasons cannot he generally practised. Or again, if the 
stubble were ploughed under, the result would he efficacious. But 
straw is valuable with us, and in very many places the soil is not 
deep enough for anything hut surface-ploughing. Bolling has been 
recommended, but it is a question whether the minute larvae and 
eggs would not escape pressure. One important matter appears, 
however, to have been overlooked by the Americans, and that is 
the presence of the puparia in the siftings from the threshing- 
machine. This was first observed by Mr. Palmer, and at once 
made public by Miss Ormerod. We cannot doubt that the debris 
contains other enemies to crops besides the Hessian fly. All such 
refuse should he burnt, and straw in manure should he well heated. 
The parasites are deemed so useful by the American entomologists 
that where the Hessian fly and parasites appear co-existent, they 
would risk retaining the fly rather than destroy the two together. 
I do not in the least sympathize with this precaution. If a thing 
must he done, and we can easily do it ourselves, why leave the 
performance to others, even to parasites ? Moreover, the burning 
of the puparia in our siftings does not disturb the balance which 
exists in neighbouring fields between the flies and the parasites. 
The fields which I have found to he the worst attacked were 
those adjoining clover, which, having been sown with barley or 
wheat, must have contained in autumn many self-sown plants, 
thus providing a suitable nidus for the brood of that season. It 
would he advisable not to sow clover with these cereals. 
It seems that the most important precautions to he taken 
are the most elementary, viz. that the seed sown should be 
of a kind giving good strong straw, and that all means should 
he taken to secure vigorous growth. This leads me to refer to the 
old Hebrew dictum of the indispensable necessity that land should 
sometimes lie fallow. The barley which suffered the most on the 
Bevell’s Hall Parm was grown on spots of poor soil, while barley 
