NO. 10 MORPHOLOGY OF GNATHOTRICHUS — SCHEDL 73 



Other topographical regions of the cranium are not defined by 

 sutures but they are somewhat limited by the occurring setae. 



Vertex.— The area on both sides of the sutura fronto-verticale, the 

 vertex (Ve), bears two groups of setae. Eleven bristles (f) are situ- 

 ated along each side of the sutura fronto-verticale. Four of them 

 are arranged in a single row along the suture; the rest occur in the 

 angle formed by the sutura fronto-verticale and the sutura metopica. 

 They are called setae verto-mediana. A single bristle widely separated 

 from the setae verto-mediana, the seta verto-lateralis (g) presents the 

 second group. Sometimes a minute hair is also visible near the latter 

 mentioned bristle. 



Gena.— The area between the sutura metopica and the occipital 

 apodeme ventro-laterally to the vertex is here designated as the 

 gena (Ge) . It bears two groups of setae, one on the level of, and close 

 to, the antennae (c) and one laterally (h) to them but widely sepa- 

 rated from them. The former consists of five, the latter of six long 

 bristles. The corresponding names are the setae geno-mediana and 

 the setae geno-Iateralis. 



Eplcranium. — The area dorsally to the genae and laterally to the 

 vertex is called the epicranium. A single bristle (i) sometimes asso- 

 ciated with a minute hair, is situated near the occipital apodeme. It 

 is called the seta epicrano-lateralis. 



THE APPENDAGES OF THE HEAD 

 THE ANTENNAE 



The antennae (fig. 37, An) arc present as small membranous lobes 

 next to the ventral end of the sutura metopica. Each bears one papilla 

 and numerous minute hairs. 



THE MOUTHPARTS 



Mandibles. — The mandibles (fig. 28) dififer somewhat from those 

 of the adults, in contrast to which only one median tooth is present 

 and the shape of the mandible is more slender and triangular. The 

 setae are present in the same number as in the adults but their position 

 in relation to each other is different. Proposed names : setae mandi- 

 bulae dorsalis and setae mandibulae lateralis. 



Maxillae. — The maxilla of the larva (fig. 38, A) is much simpler 

 in structure than that of the adult. However, all parts present in the 

 adult maxilla are also distinguishable in the larva. 



The cardo (Ca) is present as a distinct sclerite, triangular in out- 

 line and connected with the extended hypostomal ridge, the mentum 

 and the stipes respectively. This is, as in the adult, not the only con- 



