240 MONOGRAPH OF THE LABOULBEXIACE^. 
Variations in size among different specimens of a given species are often influ- 
enced by two factors; namely, the size of the host and the position in which the para- 
site has become attached. Thus small specimens of a given species of insect will, as 
a ride, bear smaller parasites than larger ones, and the same is true of smaller species 
in a varied genus, for example, like Platynus, almost all the members of which are 
liable to bo infested by a single species of Laboulbenia. In regard to differences de- 
pendent on the position of growth, it is usually true that individuals growing near the 
circulatory centres of the host, being presumably better nourished, are commonly dis- 
tinctly larger. The largest individuals that I have observed, for example, have been 
found growing on the thorax or prothorax about the base of the two anterior pairs of 
■ legs, while, on the same insect, those which inhabit the tips of the elytra, or of the legs, 
include the smallest specimens. It should also be observed that individuals growing 
in situations in wliicli they are exposed to the most unfavorable conditions are apt to 
4 
be thick-set, short, and stout, with short appendages. This is true, for example, in 
specimens of Lahoulhcnia elonrjata^ L. suhtermnca, and various other species?, when they 
occur, as they not infrequently do, on the mouth parts or near the tips of the legs of 
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their hosts, the difference in general habit in such cases being often so great that such 
forms might easily be mistaken for distinct species. The same short, stout habit, it 
may be mentioned, characterizes species which are found normally in such situations 
here j as, for instance, in the case of Lahoulhcnia parvula, Pef/rUscliicUa 
t 
hers, that are, as a rule, found near the extremities of the legs, and only 
d 
eptionally in other situations. 
, I 
The rate of growth of the LaboLdbenlaceae and the duration of their life period 
matters concerning which it is not easy to make exact observations, owing, on the one 
hand, to the difficulty of obtaining freshly hatched hosts that have not been exposed 
to nifection, and, on the other, to the uncertainties connected with the determination 
of the exact time at which the infection of the fresh hosts is accomplished. By keep- 
ing in confinement insects which have been collected with spores upon them just 
germinating and distributed on definite areas, one may estimate with considerable 
accuracy the time necessary for the fungus to reach maturity. This period, in the 
species of Laboulbenia which I have thus cultivated, has proved to be from two to three 
weeks. It is doubtless variable, however, in different genera ; those which are more 
plicated in structure requiring, for their full development, a period correspondingly 
longer ; as may well be the case, fo 
Ptliachomyces or Zodiomv 
According to Peyiitsch, freshly hatched flies confined with others infested by Sti^/ma- 
tomyces Baen were found to bear mature individuals of tlie fundus in from ten to four- 
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