Parasitic Influences on Melanoplus. 
Contribution from the Entomological Laboratory, No. 63, 
BY S.) Jo SHUN TER: 
The relations existing between the host and its parasite is an 
ever interesting source of study from a biologic standpoint. Maul- 
tiplied numbers of the former tend toward greater increase of the 
latter. When the parasites predominate, the individuals of the 
host tribe decrease; should the host disappear, the parasite must , 
follow or adapt itself to new environments. Absence of the para- 
site grants license to the increase of the host. The prevalence of 
one is directly dependent upon the other. 
In order that an estimate of the influence of this condition upon 
Menaloplus differentials might be gained, the writer while conduct- 
ing the summer field work of this department during the two 
seasons past, collected a number of the differential locust. Fifty 
were taken the first week of October, 1897, one hundred and thirty 
were collected September 3, 1898. 12 per cent. of those captured 
in 1897 had been parasitized by diptera. Of those taken in 1898, 
20 per cent. had been attacked by parasite diptera. When it is 
taken into consideration that the dates of capture were before the 
close of the active season of the the parasites, and that by reason 
of capture and confinement, some of the locusts taken were doubt- 
less saved from attack, the estimate can be regarded as conserva- 
tive. The duration of observation and number of individuals 
considered will not yet allow favorable deductions to be made 
from the 8 per cent. increase recorded this year. In localities 
where this locust was superabundant in October, 1897, the number 
of dead forms showing an unmistakable evidence of the work of 
dipterous parasites was nearly equal to those moving about. The 
number of Melanoplus differentialis that appeared in the same 
localities this season was equal to, if not greater than, those existing 
the year previous. This species of locust has been of economic 
importance annually in those regions for some years past. This 
(205) KAN, UNIV. QUAR,, VOL, VII, NO. 4, OCT. 1898, SERIES A 
