82 
Having now explained the special terms used and the system of 
classification adopted in reference to this Older and the family under 
consideration, I will here introduce a short key to the Acrididse found 
in Illinois, giving first a key to the families. 
KEY TO THE FAMILIES OF ORTHOPTERA. 
Forficulid.e. 
2. Blattidje. 
3. Mantid^e. 
4. Phasmid^e. 
families. 
A. Legs similar in length; posterior not elongated 
nor adapted to leaping ( Oursoria .) 
a. Body depressed, oval or but slightly elongated; 
wings resting horizontally on the abdomen. 
b. Abdomen armed behind with strong forceps. 1. 
bb. Abdomen not armed with forceps. 
aa. Body more or less cylindrical; much elongated. 
b. Anterior coxae much elongated; anterior legs 
raptorial; prothorax much longer than the meta¬ 
thorax. 
bb. Anterior coxae not elongated; anterior legs sim¬ 
ilar to the others; metathorax much longer 
than the prothorax. 
AA. Hind legs elongated, fitted for leaping ( Sal - 
tatoria.) 
a. Antennae long, setaceous, composed of many 
joints; apex of the female edomen furnished 
with an exserted ovipos or, usually more or 
less sword-shaped; elytra of the males fur¬ 
nished with a stridulating organ. 
b. Outer portion of the elytra bent abruptly down¬ 
ward at the sides; tip of the abdomen furnished 
with two elongate pilose setae. 
bb. Elytra sloping oblique!) 7 downward at the sides 
like a roof; abdomen with two short, but not 
pilose, articulated appendages. 
aa. Antennae shorter than the body, composed of 
less than twenty-five joints; apex of the female 
abdomen furnished with four short, horny pieces, 
two curving upward and two downward. 7. 
As it is very difficult to construct a key to the genera, 
characters that are readily observed, I will attempt to meet the diffi¬ 
culty by forming separate keys or synoptical tables; one for the groups 
or subdivisions of the family; one for the genera so far as this can be 
done with sufficient clearness to be easily understood; and one for 
our Illinois species. In each of these tables the characters are intend¬ 
ed only to include the groups, genera and species represented in Illinois, 
and the arrangement therein given is artificial. 
5. Gryllid^e. 
6. Locustid^e. 
Acrididse. 
founded on 
