260 ENTOMOLOGICAL NEWS [xxxii, '21 



labeled en in Fig. 8 is merely the cercus, en, of Fig. 4, while 

 the plate labeled pr in Fig. 8 is merely the elongated basal plate. 

 pr, of Fig. 4, etc., the exopodite, r.r, of Figs. 14, 11, etc., being 

 absent in Fig. 8. The cercus, en, of Fig. 8 is borne more 

 laterally with respect to the basal plate pr than is the case with 

 the cerci of certain other insects (c. g., those shown in Figs. 

 1, 2, etc.), but the endopoclite, en, with which the cercus is 

 homologous, is frequently borne laterally to the basal plate pr 

 in Crustacea also, as for example in the crustacean shown in 

 Fig. 10, in which the structure labeled en corresponds to the 

 cercus, en, of Fig. 8 (or to the endopodite, en, of the Crustacea 

 shown in Figs. 5, 14, etc.). while the basal plate pr of Fig. 10 

 has become elongate, suggesting a tendency to assume the 

 elongate condition of the basal plate pr of Fig. 8. The exopo- 

 dite, ex, which is very small in Fig. 10, has completely disap- 

 peared from the basal plate pr in Fig. 8. 



In comparing the immature dragonfly shown in Fig. 8, with 

 the immature damselfly shown in Fig. 9, it is evident that the 

 cercus or endopodite, en, of Fig. 8, corresponds to the cercus 

 labeled en in Fig. 9. The elongate basal plate pr of Fig. 8 

 corresponds to the basal plate pr of Fig. 9, but the exopodite, 

 e.r, of Fig. 9 is not present in Fig. 8. The exopodite ex of Fig. 

 9, which forms one of the lateral caudal gills of the immature 

 damselfly evidently corresponds to the exopodite, ex, borne on 

 the basal plate pr of the crustacean shown in Fig. 14, although 

 the exopodite, ex, of Fig. 9 is proportionately much larger, 

 having been modified to serve as a respiratory (and locomotor) 

 organ a function performed by the exopodites in many Crus- 

 tacea. In the adult damselfly, the endopodite. en, or cercus of 

 the larva shown in Fig. 9, develops into one of the so-called 

 "superior appendages," or true cerci of the male insect, while 

 the exopodites, ex, of the larva shown in Fig. 9 break off along 

 the dotted line //. leaving the basal segments pr to form the 

 so-called "inferior appendages" (paired) of the adult male. 



It will be noted in Fig. 14, that the basal plates, pr, of the 

 uropods occupy a position somewhat lateral and ventral to the 

 terminal tergite, ep. Similarly in insects, the corresponding 

 basal plates pr of Figs. 9, 8, 4, etc., occupy a position somewhat 



