XYIII. 
THE HESSIAN FLY AND ITS INTRODUCTION INTO BRITAIN. 
By Eleanor A. Ormerod, E.H.Met.Soc., E.E.S. 
Read at St. Albans , 27 th April , 1889. 
It was at Revells’ Hall, near Hertford, in 1886, that the first 
appearance of the Hessian fly ever recorded in Britain took place, 
and it was on the same farm that Mr. George Palmer (almost at 
the same time as Mr. Taylor at Daleally in Scotland) observed one 
of the simplest and most effective means of checking increase of the 
pest,—so simple and so effective that it was at once noted for 
adoption by the Director of the Government Earm Stations in 
Canada, and by the chief observer of the habits of this insect-pest 
in Russia; and in my own house I had the honour of bringing it 
under the notice of Professor Riley, the well-known Entomologist- 
in-chief of the United States of America, and of hearing from him 
that the plan was noted for adoption. 
In appearance the Hessian fly is just like a very little dark 
brown gnat (say about a quarter of the size of a common gnat), 
with a pair of smoky grey wings, three pairs of uncommonly long 
legs, and a pair of antennae or horns, very beautiful under the 
microscope by reason of their beaded structure. It is a sober- 
looking little creature when fairly launched into life, but when 
it can be watched as I have seen it in its first hours, before the 
brilliant mulberry-colour spotted with black velvet changes to the 
graver tints, it is as bright a little piece of coming mischief as may 
well be imagined. 
The attack, as we have had it in Britain, happily as yet only affects 
the growing corn in summer, not the winter plants, and consists of 
the flies laying their eggs on the stem of the corn just above a 
knot. There the little white legless maggots begin their work 
beneath the sheathing leaf, sucking the juices continuously with¬ 
out moving from one spot. There one or more remain, and the 
natural result is that the stalk is very much weakened just at the 
point of injury, and presently when the ear at the top becomes a 
heavy weight, or a summer breeze passes through the standing 
corn, the stems bend down at the weakened part. So the appear¬ 
ance in the fields of the stems sharply elbowed down just above a 
knot is the regular sign of presence of infestation. The maggots do 
not stir from where they lie feeding, their outer coats simply harden 
and change to a bright brown colour as they turn to chrysalis state ; 
and then from their size, their flattened shape, and their colour, 
they become so like the flaxseeds from which they take their name 
that when I have mixed the real and the so-called flaxseeds to¬ 
gether, it has not been an easy task to distinguish at a glance the 
one from the other. Erom these so-called flaxseeds (really the 
puparia or chrysalis-cases of Cecidomyia destructor) the flies presently 
come out,—it may be in the autumn or it may be in the following 
spring after lying quiet through the winter,—and start a new attack. 
