STRUCTURE OF THE ADULT MOSQUITO. 



THE HEAD. 



The head is more or less globose, inserted upon a slender, flexible neck, a large 

 part of its surface occupied by the eyes ; there is a prominent clypeus, the an- 

 tennas are long, and the mouthparts consist of a long sucking proboscis and a 

 pair of palpi, usually considered maxillary, inserted at its base. There are no 

 ocelli. 



THE EYES. 



The many-faceted compound eyes are large, in most species almost or quite 

 contiguous above and beneath. In front the eyes are deeply emarginate to 

 make place for the insertions of the antennae and the depth of the emarginations 

 varies with the size and place of insertion of these organs according to the 

 species or the sex. As the basal joint of the antennae is often much larger in the 

 male than in the female, in accordance with this the emargination of the eyes 

 is deeper in that sex. 



Aside from the emargination the eyes of the two sexes usually differ somewhat 

 in shape and those of the female may be somewhat larger than those of the male. 

 In the culicine tribe the eyes are markedly broadest at the sides and are much 

 narrowed above the antennae, particularly in the male ; beneath they are broad 

 and may be contiguous in their whole width. In the Sabethini the eyes are 

 nearly as broad behind the antennae as at the sides and the sexual differences are 

 less marked. In certain genera of this tribe the eyes are broadly contiguous be- 

 hind the antennae ; in other forms a chitinous wedge is inserted between the eyes 

 in such a manner that the eyes touch at their hindermost angles and diverge 

 towards the front. In a curious sabethid from the Philippine Islands, HeiZ' 

 mannia scintillans, the eyes are separated above by a broad strip of chitin, 

 almost a third the entire width of the head. In the Culicini the eyes, when 

 contiguous above, are never contiguous along the entire margin. The chitin of 

 the occipital region is produced wedge-shaped between the eyes ; when this wedge 

 is small the eyes are contiguous, when large they are separated, the separation 

 being usually greatest at the broadly rounded hind angles. In this tribe the 

 median suture of the occiput may be seen continuing forward between the eyes 

 thus clearly indicating that the intra-ocular wedge belongs to the occiput. In the 

 Sabethini, as already mentioned, a wedge is inserted anteriorly and the eyes are 

 approximated at their hind angles. 



In addition to the compound eyes there are present a pair of rudimentary or 

 vestigial eyes. These are situated laterally, close to the hind margin of the 

 compound eyes. They are covered by the scale vestiture of the cheeks and are 

 therefore not visible; however, they become plainly visible in a balsam prep- 

 aration in which the pigment of the eyes has not been destroyed. These vestigial 

 eyes consist, in fact, wholly of groups of pigment cells; there does not appear to 

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