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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I37 



other types this role is taken over by the mandibles in great part; 

 (5) the weak sclerotization of the hypochilum, permitting some dila- 

 tation of the cephalic cavities, while its homologue in the other types, 

 strongly sclerotized, is opposite to the mandibles. 



The Chironomidae larvae present in their feeding organs four 

 structural types (Gouin, 1956) : the orthocladian, podonomian, 



J^Sl\ 



M Cib. 



M Prm 



Fig. 12. — Macropdopia cf. nehulosa Mg. 



Part of a lateral sagittal section. It shows the relationships of antenna partly 

 invaginated and innervated {A) with the mandible {Md) and maxilla (Mt), 

 of which the section, passing to the outside of the palpus, grazes the stipital 

 muscle (M Sti) very close to its insertion; the maxillary plate {PI Mx), a kind 

 of fold of the cranial wall, supports the basal maxillary sclerite. In the thickness 

 of the integumental membrane, the mandibular adductor tendon (TMd). Near 

 the premental muscle, some nerve elements. 



chironomian, and the tanypin types. The anatomy of the digestive 

 tract (Gouin, 1946) shows a very clear parallelism: the Tanypinae, 

 in effect, form again a type well defined by the great voluminous 

 mesenteric cells with papillae situated behind the cardiac valve (Gouin, 

 1946a, fig. VII). On their part, the Chironominae present a "style" 

 of their own and particularly the very richly differentiated structure 

 of the cardiac valve, mesenteron, and proctodaeum, so clearly different 

 from the anatomically simple intestine of the orthocladian and podo- 



