590) VICTOR E. SHELFORD 
4. The relation of local and geographic distribution 
We have suggested in the case of the three species here consid- 
ered, that the geographic distribution of each is the geographic 
distribution of the conditions in which it lives and breeds. We 
have visited several of the different climatic realms in which each 
of these three and many other species occur. So far as ordinary 
observation can go, the breeding and general living conditions 
are similar in the different localities, even though the climate, as 
in the case of Cicindela tranquebarica, is very different. The 
same conditions are found by the species through its moving near 
to water in the arid climates, as compared with the more moist 
climate. 
It is customary to conclude that condi ions are the same because 
the species is the same. Here we have tried in a general way to 
determine whether the species is the same throughout its range, 
by the study of the condition, and experimentation on the animals. 
This is the only mode of attack that can yield definite results. 
It is highly desirable, however, to carry the observations onsoil 
and other environmental factors further with the use of physical 
factor instruments. It is equally desirable to conduct actual 
experiments on each species of beetle at a number of points, 
especially those near the outskirts of its geographic range. This 
would, no doubt, reveal differences of detail which we have over- 
looked, but which cannot, so far as present observation goes, be 
of great importance. 
5. Factors governing geographic distribution 
Our data show clearly that the breeding pe iod is crucial as 
determining the local distribution, and that an excess or deficiency 
in any one factor is sufficient to decrease the number of individ- 
uals present, or cause them to be absent entirely. Any factor dif- 
fering sufficiently from the optimum for a given species is sufficient 
to limit its distribution. There can be no important difference 
whether a deficiency in moisture is due to insufficient rainfall 
or to distance from or height above water, or whether an excess 
of temperature is due to latitude or exposure and accordingly the 
same factors must govern both ocal and geographic distribution of 
the tiger beetles. 
