1912] Mitir and Kershaw — Development of Mouthparfs in Homoptera 81 



Sd day. (Fig, 1). On the second day the embryo is invaginated 

 and Hes on the dorsal side of the amniotic cavity and faces the 

 ventral side of the egg, the head pointing posteriorly. The trophi 

 and legs are fairly well developed, the clypeo-labrum being a 

 median (apparently undivided) prominence of the cephalic lobes, 

 forming the dorsal boundary of the oral cavity. The mandibles 

 are plain, round, undivided processes or protuberances (^man) 

 forming — together with the maxillse — the lateral boundaries of the 

 oral cavity. The maxillae already have a constriction indicating 

 their future development into the maxillary plate (map) and the 

 maxillary setae (Max). The labrum (forming the ventral bound- 

 arj^ of the oral cavity) is divided from its base and is very similar 

 to a pair of legs. The abdomen is not distinctly segmented, is 

 very long and ventrally flexed towards the head. 



Sd day. The protuberance forming the clypeo-labrum has be- 

 become somewhat pointed in the middle and the constrictions 

 between the maxillary-setae and maxillary-plates have further 

 deepened (Fig. la). The abdomen has become more compact. 



Jfth day. (Fig. 2). The procephalic lobes and clypeo-labrum 

 have come forward, and the maxillary setae and maxillary plates 

 are well developed. The joints of the legs are indicated and the 

 abdomen is fully segmented. 



5th day. (Fig. 3) . The clypeo-labrum is further developed and 

 the labrum is indicated. The trophi have largely developed, the 

 legs are not much altered but the labrum has begun to coalesce 

 at the base. Between the oth and 6th day the revolution of the 

 embryo takes place. 



6th day. (Fig. 4). The embryo is now in its final position, its 

 ventral side towards the ventral aspect of the egg and its head 

 pointing anteriorly (Fig. 10). The distal joint of the antenna has 

 thinned and lengthened remarkably; the labrum is differentiated 

 from the clypeal region; the mandibles and maxillary setae are 

 long, pointed rods. The maxillary plates and the pharynx and 

 clypeus have grown forward still more, forming between them the 

 sulci in which the setae lie. The labrum has wholly coalesced 

 except at the tip, the edges have begun to turn up to form a trough, 

 and the joints are discernable. 



7th and 8th days. There is nothing striking to record. 



9th day. The eyes are beginning to pigment, the edges of the 



