222 



ORTIIOPTERA 



Heterogamia is replaced by an ocellus. The antennae are very 

 elongate and consist of a large number of minute rings or joints, 

 frequently about 100. The head is not inserted directly in the 

 thorax, as is the case in so many Insects ; but the front of the 

 thorax has a very large opening, thus the neck between it and 

 the head is of more than usual importance ; it includes six 

 cervical sclerites. 



The pronotum is more or less like a shield in form, and 

 frequently entirely conceals the head, and thus looks like the 

 most anterior part of the body ; usually 

 it has no marked angles, but in some of 

 the apterous forms the hind angles are 

 sharp and project backwards. In contrast 

 to the pronotum the prosternum is small 

 and feeble, and consists of a slender lateral 

 strip on each side, the two converging 

 behind to unite with a median piece, the 

 prosternum proper. [N'one of these pieces 

 of the ventral aspect of the prothorax are 

 ordinarily visible, the side -pieces being 

 covered by the inflexed head, and the 

 median piece by the great coxae. In 

 some of the winged Blattidae {Blabera, e.g.) 

 there is at the base of each anterior coxa 

 a small space covered by a more delicate 

 membrane, that suggests the possibility 

 of the existence of a sensory organ there 

 (Fig. 120, i)} At the base of above 

 and behind the front coxa the pro- 

 thoracic spiracle is situate. 

 The meso- and meta-thoracic segments differ but slightly from 

 one another ; the notal or dorsal pieces are moderately large, 

 while the sternal or ventral are remarkably rudimentary, and are 

 frequently divided on the middle line. Connected with the 

 posterior part of each sternum there is a piece, bent upwards, 

 called by some anatomists the furca ; when the sterna are 

 divided the furca may extend forwards between them ; in other 



Fig. 120. Base of front leg 

 and portion of prothorax 

 of Blabera gigantea. a. 

 Under-side of pronotum ; 

 h, fold of pronotum ? ; c, 

 epimeron? ; d, episternum ? ; 

 e, trochantin ; /, coxa ; 

 g, trochanter ; h, base of 

 femur ; i, presumed sense 

 organ. 



^ This enigmatic structure is similar in position to tlie aural orifice of Locustidae 

 (see Fig. 101) ; but it is closed by a transparent membrane, whereas the ear orifice 

 of Locustidae is, as we shall subsequently see, quite open. 



