145 
tion of preserving the proper balance between life of all descriptions, 
nature itself Las intervened to prevent the undue increase of the para- 
sites, either by making them less fertile than the hosts upon 
which they prey, by giving them a smaller number of broods, or bj~ 
supplying them in turn with parasites which keep them in check. 
This secondary parasitism is well known and it is as effective in pre- 
venting the excessive increase of the primary parasites as these are 
in inventing the excessive increase of the original host. There is 
really almost as much danger, and that is very little, that the sec- 
ondary parasites will destroy the primary parasite as that the primaries 
will exterminate their host. Predaceous insects are in much the same 
case, they never entirely destroy the species they feed upon, and in 
99 cases out of 100 they conquer their prey after all the injury has 
been done to the growing crops. Let us take the case of the Melon 
Louse for example. This makes its appearance in June or July, and 
increases with marvelous rapidity. Very soon after various species of 
Coccinellids make their appearance and begin preying upon the plant 
louse; but in the number in which they first appear they are incapable 
of- eating up the lice as fast as they multiply. By September they are 
up with their prey, but then it is too late; the crop has been destroyed 
and, although it is quite probable that the late broods have entirely 
rid the vines of plant lice, yet it has not benefited the farmer one 
solitary cent. I had a beautiful opportunity of observing just this in 
1892. It was a pleasure to see how the late broods moved from vine 
to vine, leaving scarcely a living louse behind them; but that same 
vine was dried and withered ; whatever fruit there remained on it was 
undersized, blackened by honey-dew, half ripe, and never in fit condi- 
tion for market. Acre after acre I have seen in just that condition, 
and practically no revenue has been derived from the land. It is 
quite true that the beetles exterminated or nearly exterminated the 
plant lice, but this did not advantage the farmer one solitary cent. A 
few buckets of kerosene emulsion liberally applied early in the season, 
Avhile the plant lice were running away from the lady-birds, would 
have been of a great deal more money benefit than all the aid that 
nature gave. My contention is, that in dealing with injurious insects 
from the farmer's standpoint, we can entirely ignore the work of para- 
sites or predaceous insects. We must accept the fact that each year 
these insects will appear in about the same numbers; that nature has 
evidently assumed that this is about the proper number to appear, and 
that all her checks are arranged accordingly. If we wish to lessen 
them, we must do it by means other than those which she has provided. 
There is, of course, a possibility that we may in some cases make use 
of either parasites or predaceous insects. That has been very well 
illustrated by the instance before referred to, that of the Vedalia and 
the Icerya. The one point that is overlooked by the majority of those 
who see only newspaper accounts is, that we had to deal in the first 
