43 
grasshoppers being only the various stages of certain leaf hoppers 
—by far the commonest species being the unfriendly leaf hopper 
Jassits inimicus. 
As has so frequently been the case when our indigenous locusts 
have become destructively numerous, many people mistook them 
for the Rocky Mountain locust, and were unnecessarily alaime 
concerning future attacks by this frightfully destructive pest. It 
seems useless to reiterate what has so frequently been said on tins 
subject—that the Kocky Mountain locust has never, and m all 
human probability can never, become injurious m Illinois. 
, conclusions. 
The following general considerations bearing upon the subject of 
the destructive outbreaks of our indigenous locusts, and of the possi¬ 
bility of forecasting the future in any given locality where these 
insects are numerous, are mainly the result of the investigations re- 
corded above. Of course no definite rules can be laid down by which 
predictions can be made. We can only _ indicate some of the fac¬ 
tors- to be taken into account m estimating the ratio of pioiab - 
ity In all cases the entomologist must carefully survey the field, 
and use his own judgment as to the importance due to each fac¬ 
tor of the problem. 
Besides the arthropodous animals mentioned below, various other 
agencies—such as the weather, epidemics of contagious diseases, 
•etc.—must at times be taken into account. 
1 Destructive outbreaks of our common locusts are liable to 
•occur in restricted localities at varying intervals, whenever tlie 
climatic and other conditions favor their development, 
2. There will generally be a gradual increase in the numbers 
•of the locusts for a series of years, until the culmination is reached, 
after which there may be expected a great and sudden decrease. 
3. The great majority of the eggs are deposited in grass lands, 
—especially in pastures and along roadsides,—and these situations 
should be examined for the eggs. Here, also, the young locusts 
will appear at a time when they are most easily destroyed by 
artificial means. 
4 As a concomitant of this locust increase, there will usually 
be an increase’ of the Arthropoda which prey upon the locusts or 
their eggs; and it is generally owing to the fact that these enemies 
get the start of the locusts that the outbreak is checked. 
5. Among the more important of these locust enemies which 
should be observed, and reckoned upon in prognosticating, are 
4he following: 
a The red locust mite ( Trombidium locustarum), which, when 
young, attaches itself to the locusts and sucks their juices; and 
later attacks their eggs. 
