152 COMPARATIVE ANATOMY 



great number of minute hexagonal facets. In all essential 

 characters the structure of the compound eye of the cockroach 

 is the same as that of Astacus. The antennse are attached to the 

 front of the head immediately below the eyes. Each antenna 

 consists of a tolerably stout basal joint movably articulated 

 by a ring of soft cuticle to a cavity in the clypeus. _ The basal 

 joint is succeeded by as many as seventy-five to ninety small 

 joints beset with bristles. In the male the antennae are rather 

 longer than the body, but in the female they are shorter. To 

 the inner and upper side of each antenna is a small circular 

 area of white colour, situated at the end of the suture dividing 

 the epicranium from the clypeus. These areas are called the 

 fenestras. They are covered by soft cuticle, and are supposed 

 to represent aborted ocelli, but their function and significance 

 are altogether doubtful. The mandibles are stout curved bars 

 articulated partly to the posterior downward extensions of the 

 epicranial plates, partly by an anterior joint, to the clypeus. 

 Their inner edges are strongly toothed, and they work from 

 side to side ; when approximated they are entirely covered by 

 the labrum. The first pair of maxillse are articulated to the 

 epicranium behind the mandibles. Each maxilla consists of 

 a two-jointed base bearing an inner and an outward branch, 

 and it would be convenient to call these by the same names as 

 the parts of the crustacean limb with which they are apparently 

 homologous — namely, protopodite, endopodite, and exopodite. 

 But entomologists have adopted- a different nomenclature, and 

 therefore we must call the proximal joint of the protopodite 

 the cardo, the distal joint the stipes, the exopodite the palp. 

 The endopodite is divided into an inner pointed blade furnished 

 with stiff bristles along its inner border, the lacinia, and an 

 outer softer and longer portion called the galea. The palp 

 consists of five setose joints, of which the first two are the 

 shortest. The second pair of maxillse are constructed on the 

 same plan as the first, but the protopodites and endopodites 

 are fused together in the middle line to form a flat-jointed 

 plate called by entomologists the lower lip or labium. The 

 fused coxopodites, corresponding to the cardines of the first 

 maxillae, are called the sub-mentum, the fused basipodites, the 

 mentum, and the partially fused endopodites are called the 

 ligula. Each half of the ligula is further divided into an outer 

 moiety, the paraglossa, corresponding to the galea of the first 



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