Walter Ritchie 



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palpifer (If) with a few bristles; this palpifer carries the two-jointed 

 labial palps (Ip) and the ligula (I) densely covered w r ith bristles. The 

 submentum (sm) is posterior to the mentum, while surrounded by these 

 two portions and by the cardo (c) and stipes (st) is an area somewhat 

 circular in shape, the maxillary sclerite (mxs); the exact demarcation 

 lines of this last named portion are in most cases difficult to make out. 



If the mandibles and ventral mouth parts described above be removed 

 and the under surface of the head (Fig. 8) examined, one can make out 

 in the centre a large opening, the occipital foramen (of) through w r hich 

 may be seen the head muscles (hm) ; between this foramen and the 

 maxillary foramen (mf), now clear to view, lies the region called the 



Fig. 7. Maxillae and labium of S. carcharias larva (greatly magnified), c = cardo; I = ligula; 

 Zrt=lacinia; lf = labial palpifer: Zp=labial palp; momentum. mp~ maxillary palp; 

 mxp — maxillary palpifer; mx8= maxillary sclerite; sm = submentum ; .<tf = stipes. 



gula (g); its lateral sutures diverge posteriorly and meet the tentorial 

 region (t) ; beside the gula, on each side, lies the hypostome (hs) with its 

 external suture convex. 



Other portions seen in this view of the head, already referred to in 

 describing the dorsal view, are the pleurostome (ps), lying on the lateral 

 margin of the maxillary foramen (mf); the clypeus (c), the labrum (I), 

 attached to which are two strands of chitin called the labral hooks (Ih), 

 the ocelli (o) and the ventral portion of the epicranium (epi). 



The Thorax (Fig. 3, a). 



In side view, immediately following the chitinous head piece we have 

 the prothoracic, the mesothoracic and the metathoracic segments. Of 

 these three segments the prothoracic is far the largest, being nearly equal 



