MORSE: ORTHOPTERA OF NEW EXC.LAXD. 243 
regarded as sympathetic, since these creatiin's, though chiefly 
nocturnal, often live anionp; brown fallen leaves. 
The Locusts (Acrididae) present a wide variety of hues and 
require consideration more at length. With reference to colora- 
tion, a Locust presents three classes of surface: 1st, the ventral 
part of the body next its support of earth or plant,— this is 
shielded to a great extent from external influences such as the 
action of light and the observation of birds and other enemies; 
2d, those parts continuall}' exposed, day and night, at rest and 
in action, to light and observation, comprising the dorsal, lateral, 
anterior and posterior surfaces; 3d, those parts exposed only 
occasionally, and usually for brief periods only, during attack, 
courtship, or other exciting circumstances, or while in rapid 
motion, comprising the wings, hind tibiae, inner and under sides 
of the hind femora, and sides of the base of the abdomen. 
The coloration of each of these surfaces needs to be studied in 
correlation with that of the others and with direct observations 
on the habits and distribution of the insects in the field. That of 
the first class of surfaces (ventral part of the body) has re- 
ceived scant attention, much less than it deserves. A very large 
proportion of animals, Locusts among them, exhibit the phenom- 
enon of "counter-shading." In this type of coloration the ven- 
tral side of the body is paler and less varied in tint than the dorsal, 
and this paleness serves to offset the intensity of light received 
from above and efface the solidity of the animal through diminu- 
tion of the shadow due to its roundness. The paleness is due 
primarily to lack of exposure to light and consequent slight devel- 
opment of pigment on that part of the body; it is secondarily 
protective in function as it helps in the majority of vertebrates 
and many invertebrates to obliterate the form of the body. 
^Yhile most Locusts exhibit counter-shading in some measure, 
there are a few conspicuous exceptions in New England, partic- 
ularly^ the species of Arpkia, and to a less extent Encoptolophus, 
in which the ventral surface is black or very dark. Possibly 
this is to be explained by the form of the body of a Locust as 
contrasted -^-ith that of most vertebrates, — triangular in vertical 
cross-section, the base placed on the ground, — and the habit 
which these insects have of resting directly on a dark soil, thereby 
effectively shutting off hght from below or beyond, which would 
bring them into relief. 
