NO. 8 ANATOMICAL LIFE OF THE MOSQUITO — SNODGRASS 19 



(1944a) calls it the "palpiger," but it might be referred to the cardo, 

 though no muscles are attached on it. 



The principal functional features of the culicid larval maxillae are 

 their setal brushes and combs, which serve to collect food particles 

 from the labral brushes. In the predaceous Toxorhynchites the 

 maxillae (fig. 6 F) are similar to those of other species, but they are 

 greatly reduced in size (fig. 4E, Mx). The palpi are presumably 

 sensory organs, but their disparity in size, as between Culex (fig. 6 C) 

 and Anopheles (E), for example, is difficult to explain. The princi- 

 pal movements of the maxillae are in the transverse plane. 



The labium and hypopharynx. — In most adult insects the salivary 

 duct opens between the bases of the hypopharynx and the labium. In 

 some larval insects, as in caterpillars and hymenopterous larvae, the 

 labium and hypopharynx are united in a single suboral lobe traversed 

 by the duct of the salivary, or silk, glands, which opens at the tip 

 of the composite lobe. The same is true of some nematocerous fly 

 larvae, as is well seen in the tipulid (fig. 7 A, SIDct). In the mosquito 

 larvae the combined labium and hypopharynx are reduced to a flat or 

 somewhat protruding vertical surface between the mouth and the 

 hypostomium, with the salivary duct opening on it. The salivary 

 orifice, therefore, separates the dorsal hypopharyngeal component 

 from the ventral labial component. 



The hypopharynx (fig. 7 B, Hphy) is supported by the hypopharyn- 

 geal bars (hb) from the lateral cranial walls; immediately above it is 

 the wide mouth (Mth) opening into the pharynx. The labial area 

 below the hypopharynx (D,E, Lb) is variously developed, usually 

 strongly sclerotized and armed with spines or teeth. Other writers 

 have well illustrated the details of the labial structure in different 

 mosquito species. Some have attempted to analyze the larval labium 

 into the parts of a typical insect prementum, but their results are 

 not fully convincing. At C of figure 7 is shown the labiohypopharyn- 

 geal complex of Toxorhynchites rutilus in dorsal view, in which the 

 salivary duct (SIDct) is seen opening between the two component 

 parts. Attached laterally on the base of the labium are the tendons of a 

 pair of muscles from the ventral head wall, as in the tipulid larva (A). 



Inasmuch as all the cranial muscles of the insect labium are inserted 

 on the prementum, the labium of the mosquito larva is evidently the 

 prementum; the hypostomium and the ventral head wall, as already 

 shown, being no part of the labium. Menees (1958a), however, has 

 argued that the ventral head area behind the hypostomial lobe must be 

 the labial submentum because the labial muscles have their origins on 



