58 
been the fungous disease, Lmpusa aphidis, which was common the 
early part of the season upon this insect, in both clover and pea fields. 
It is a contagious disease, and destroys the pest in very large numbers, 
under certain conditions. In one instance we found 58 dead lice upon 
the under surface of a single lobe of a clover leaf, and it was not an 
uncommon thing in June to find 15 or 20 dead lice upon the under 
surface of a pea leaf. With the rains which prevailed throughout this 
section during June, which fostered the development of this disease, 
it spread rapidly throughout the infested fields, and as a consequence 
it was very difficult to find the pea louse upon late peas. A careful 
examination of peas where the insects were abundant in June showed 
that they were practically free from them. We feel, therefore, that 
the climax, as far as the development of the insect this season, has 
been reached, and that these silent factors in nature are now actually 
reducing the pest to such a point that it may possibly be several years 
before it will be such a destructive pest in this section as it has been 
for the past two seasons. At any rate, the conditions are such that 
the farmer and canner have taken new hope, and we trust the future 
will bring fewer lice and more peas. 
In discussing this paper Mr. Hopkins said it would be interesting to 
know whether it is possible for this to be an introduced pest, and 
asked Mr. Johnson whether he had made any investigations in that 
respect. : 
Mr. Johnson replied that his opinion is that it is not an introduced 
pest but an indigenous insect, and that the change of conditions has 
brought about this enormous development in numbers. 
Mr. Hopkins asked if there are any records of its previous occur- 
rence in great numbers. 
Mr. Johnson stated that the only record he has is one by Mr. Beck- 
with, formerly of the Delaware station, made ten or twelve years ago, 
and the record of its occurrence along the Potomac River in 1887. In 
neither case however, are we sure that it is the same insect, as speci- 
mens are not available. The growers of Maryland, Delaware, and 
Virginia state now that this insect has been known to them for a 
number of years. 
Mr. Hopkins said this case is such a complete parallel to the inva- 
sion of the pine-bark beetle, which has been fully presented and pub- 
lished and the trouble from which is now over, that it occurred to 
him that in this case within the next few years this insect will proba- 
bly disappear or become exceedingly rare. He had taken the trouble, 
in connection with the investigation of the pine insect, to look up the 
history of invasions by indigenous insects and found that they multi- 
ply rapidly for several years, become enormously destructive, anda 
