418 



Median Lobe. — This term is used for convenience and includes the 

 fused glossae and paraglossae. 



Hvpopluirvnx. — Perliaps the most conspicuous ])ortion of the 

 hypopharynx is a circular pad between the tips of the maxillae, and 

 easily seen on raising the mentum-ligula. It is covered with minute 

 setae possibly indicating the location of sensory organs. The pad has 

 been given the name laniinula !)y Uerlese, and corresponds to the lingua 

 of other insects. However, it is somewhat difficult to homologize any 

 part of it with other forms on account of the very great modification. 



Propharxnx. — The propharynx lies closely applied to the ental sur- 

 face of the labrum, and has essentially the same shape as the latter. 

 It possesses no features worthy of mention. 



Prothorax. — The prothorax, the large segment just caudad of the 

 head, is preceded liy a smaller segment, the microthorax, which forms 

 the neck. The sclerites of tlie microthorax are not well developed in 

 the nymph. Most of the sutures of the prothorax are also indistinct 

 and are represented by furrows in the cuticle. The pronotum (Fig. 

 23, pme) is divided by depressions into caudal, mesal, and cephalic 

 areas. The caudal lol)e is, in most species, a narrow transverse area 

 along the caudal margin; the mesal lobe comprises the larger part of 

 the pronotum, and is usually divided by a median furrow into two 

 lateral areas; and the cephalic lobe includes the transverse area 

 cephalad of the median lobes rind caudad of the cephalic margin. The 

 furrow which marks the caudal boundary of the cephalic lobe and the 

 median furrow of the pronotum form a Y, and at the point of union 

 of the three arms there is usually an invagination. The proepimera 

 and proepisterna are areas vcntrad of the pronotum on cither side and 

 dorsad of the coxae, and are separated by furrows which are very dis- 

 tinct in some genera, especially Lestes. In this genus the furrow sep- 

 arating the two pieces extends dorsad a short distance from the point 

 of articulation of the procoxae and the procoxal process (P'ig. 25, 

 pcxp), bends slightly cephalad and then caudad, extending to the caudal 

 margin of the prothorax. In the Coenagrioninae there is often a sec- 

 ondary ridge extending dorsad from the procoxal process but this does 

 not mark tlie boundary between ])roepisternum and procpimcron. The 

 prosternum is the area between tlie procoxae, and is much broader than 

 that of the adult. There is no indication of distinct areas or sclerites, 

 but near the caudal margin of the prosternum and between the coxae 

 are the two invaginations of the furca (Fig. 24, fi). 



Mesothorax and Mctathorax. — The mesothorax and metathorax 

 are greatly different from the common type of thorax, in consequence 

 of an approximation of the mesepisterna on the dorso-meson in the 



