86 MOSQUITOES OF NORTH AMERICA 



ing simultaneously. When these muscles contract the seta-hearing area of the 

 flabella is depressed and the setge come together in a bmsh whose tip points 

 caudad. On their relaxation the flahellse protrude beyond the front of the head 

 and the setge stand out in great yellow fans. The median prominence or pala- 

 tum passively follows the movements of the flabella, which are strictly syn- 

 chronous, as far as I have observed." 



The palatum is clothed on its dorsal surface with short but coarse spine-like 

 hairs ; ventrally is inserted a dense tuft of long pendant hairs which swing in 

 unison with the lateral brushes. In the region of the epipharynx are two 

 fringes of dense hairs arranged in closely approximated longitudinal series. Ac- 

 cording to Easchke the epipharynx when in repose reaches down to the hypo- 

 pharynx and closes the mouth. In swallowing, the epipharynx is raised and 

 drawn back by two muscles inserted at its base. 



The mandibles are large and elaborate in structure. In a ventral view they 

 lie behind the maxillge and are in large part hidden by them. They are very 

 broad and situated well apart. The apices facing each other bear a group of 

 projecting irregular teeth and near these on the outer side a large movable spine 

 is inserted. Below the teeth there is a broad truncate chitinous projection. On 

 the dorsal margin is a series of seta-bearing tubercles and at the outer angle 

 several long spines. On the inner side there is a fringe of long hairs, inserted on 

 a crescentic chitinous ridge near the apical margin, which helps to sweep the 

 food into the mouth. The mandibles are moved by two pairs of powerful 

 muscles. A muscle attached to the lower inner angle draws the mandible down- 

 ward and inward, another muscle at the outer lower angle draws it outward. At 

 their opposite ends the muscles are broadly attached in the posterior part of the 

 head to the epicranium walls. 



The maxillge are large but very simple, showing none of the components trace- 

 able in most mandibulate insects. They are flattened, roughly conical with a 

 small basal appendage, the maxillary palpus, on the outer side. The maxillae 

 are situated upon the apical ridge of the under side of the hypocranium and 

 cover the mouth from beneath. Like the mandibles they are well separated, 

 leaving an open space between them, which is however closed by projecting hairs. 

 There is a longitudinal suture and the surface is more or less hairy, particularly 

 towards the apex where the hairs are dense and long. The small palpus bears 

 at its apex several spine-like sensory appendages. Easchke does not think that 

 this palpus can be homologized with the maxillary palpus of the typical mandib- 

 ulate insects and he points out that different components of the maxilla of 

 such insects can not be traced in the maxillgs of the mosquito larva. The 

 maxillge are broadly attached to the hypocranium by a membrane and but 

 slightly movable. Two weak muscles effect the movement of each maxilla, both 

 inserted at the middle of the base and passing back are attached posteriorly to 

 the epicranium walls. 



A broad median region of the hypocranium, bounded by strong longitudinal 

 sutures, constitutes the mentum. 



At the attachment of the maxillge the hypocranium tenninates in a sharp 

 transverse ridge, somewhat lobed outwardly from the maxillaj. Behind this 



