12 
cent bore one or two colonies, and that 5 per cent were free from 
the insects. 
Infected mealybugs were first detected in this grove upon the fruit. 
Later in the season they were found nearly as abundantly upon the. 
twigs and branches, where, however, they were detected with diffi- 
culty, owing to the neutral gray color of the fungus, which simulates 
rather closely the bark of the trees. Upon the grapefruit the dead 
bugs may occur singly, or more often in groups of four or five, hud- 
dled tog-ether as in life. Surrounding them upon the grapefruit a 
dark halo was often observed, which might easily be confused with 
the sooty mold that accompanies the insect. This appearance, how- 
ever, is caused by masses of eonidia which are discharged in enor- 
mous numbers and fall upon the grapefruit near or upon one another 
(PI. I. 21). Dead insects upon the twigs and branches occur more 
often singly, most abundant in positions near the colony, but often 
from 5 to 10 feet away, and in such locations, owing to their small 
size, inconspicuous color, and position in the crevices of bark, are 
easily overlooked. 
In studying this insect infestation during the period June 13 to 
August 8, one of the first facts which became apparent was the grad- 
ual disappearance, week by week, of young insects or crawlers. The 
total number of insects collected on June i^2 and June 29 was some- 
thing over 1,500, one-third of which were so young that they were 
discarded for reasons noted below. In later collections the percentage 
of young ones decreased markedly until, on August 8, but few young 
crawlers were observed in the field. It will be observed by reference 
to Figure 1 that this period of maximum abundance of young insects 
is likeAvise the period in which the percentage of diseased specimens 
jumped from 18 to 64, and it is to be noted that following this sudden 
increase in mortality the young or crawler insects became less and less 
l umerous. 
In order to obtain definite data regarding the prevalence of the 
fungus at various periods during the season, so that its work might 
be measured with some accuracy, the following plan was adopted : 
Collections were made at approximately weekly intervals, an attempt 
being made to have them representative of the entire grove. The 
mealybugs were scraped by a penknife from the grapefruit or twigs 
to which they were attached and placed in ordinary pasteboard pill 
boxes. Preferably those grapefruit were chosen upon which large 
numbers of insects occurred, in order to facilitate the collection, but 
late in the season it became rather difficult conveniently to collect 
large numbers, as the colonies were decimated and the individuals 
scattered. In collecting the insects those dead and alive were scraped 
off indiscriminately, and when taken to the laboratory the crawlers 
or very small active members were discarded, and those infected with 
