288 
Wherever these are lacking the species is absent. In southern New Jersey 
where sandy deposits are of practically universal occurrence Psinidia is 
common, while on the opposite side of the Delaware River in Pennsylvania 
it is unknown. <A case like this shows us how essential it is that we should 
have accurate local data before we can be certain of the exact range of a 
species. 
The studies of Morse, Hancock, Rehn, Hebard, Vestal and others have 
clearly shown the intimate relation between the distribution of numerous 
Orthoptera and certain features of the environment. As Shelford has so 
well pointed out the success or failure of a species in any place will de- 
pend on how closely the environmental complex approximates to that con- 
dition at which the normal physiological activities of the species can be 
carried on to the best advantage. Where this state of affairs obtains the 
species will attain its maximum abundance; if one or more of the factors 
of the environmental complex are less favorable it will be present in 
diminished numbers, while if any essential factor is prohibitive the species 
will be absent. It is the aim of biogeography to explain the facts of or- 
ganic distribution in terms of physiology, as an expression of the re- 
actions of organisms to the varying conditions of their surroundings. In 
the case of the Orthoptera this can be done only when we know much more 
than we do now about the intrinsic qualities of the species and their 
ability to accommodate their activities to varying intensities of euviron- 
mental factors. To acquire such knowledge will require much experi- 
mental investigation. In the absence of such knowledge we must mean- 
while be content to record the facts of distribution as actually observed 
and to point out any correlation which may exist between the range of 
species and the different types of environments. By the accumulation of 
data along these lines a good foundation will be Jaid for the ultimate 
causal interpretation of distribution and kindred biological problems. 
In the present article I have endeavored not only to give a full list 
of the species observed about Lafayette, but in addition to point out the 
more evident physical and botanical features of the region with which the 
local distribution of the Orthoptera is correlated. Most of the facts here 
given were gathered by myself, but I am also indebted for some valuable 
additional data to Mr. ’. W. Mason, Instructor in Entomology at Purdue 
University, whose kindness in placing his notes at my disposal I here take 
pleasure in acknowledging. 
