94 MOSQUITOES OF NORTH AMERICA 



differ greatly according to the genera and species and these differences are 

 brought out in the systematic part of this work. 



The lateral comb of the eighth segment shows great variation, not only in the 

 shape of the scales, but their number and arrangement. The scales may even be 

 absent altogether, as in JoMotia, where they are represented by single spinose 

 tubercles, or in Megwrliinus by a chitinous plate. In other cases, as Uranotmnia 

 and Anopheles, there is a plate with a series of teeth along the margin. The 

 larvae of Bancroftia are remarkable in that both comb-scales and plates are 

 present, and in the last stage chitinous dorsal plates are also present on the sixth 

 and seventh segments. 



On the ninth segment the chitinous plate differs greatly in shape and size in 

 the last stage larva of different species. It may completely encircle the segment 

 or be reduced to a dorsal saddle. In some forms there is a group or row of spines 

 or scales, laterally along the hind margin ; in Megarhinus these form an elabo- 

 rate fringe. Laterally, on each side, is usually inserted a small hair or hair-tuft, 

 occasionally this becomes conspicuous. The ventral brush also varies much in 

 development ; in some eases it is continued into the chitinous plate, in others it 

 is much condensed. In some cases the ventral brush is inserted upon a separate 

 chitinous plate which is perforated for the insertions of the hair-tufts. In the 

 Sabethini there is no ventral brush but only a pair of lateral tufts or hairs below 

 the margin of the dorsal plate. 



The tracheal gills show great modifications in adaptation to larval habits. In 

 certain larvae which do not come to the surface for air the tracheal gills are very 

 large and are traversed by a large trachea. In other forms they are obsolete and 

 only represented by fleshy papillae. This is particularly true of the species in- 

 habiting saline water. 



The larva of Sahethinus is remarkable in the presence of a pair of chitinous 

 hooks upon the seventh segment, situated upon fleshy tubercles, dorsally, near 

 the end of the segment. In some larvae the entire integument is covered with 

 minute hairs or spicules and this may also be true of the plate of the ninth seg- 

 ment and sometimes of the breathing tube. 



In certain larvae there are small chitinous plates at the insertions of the large 

 hairs on the thorax and sides of the abdomen. These plates are particularly well 

 developed in Megarhinus and Aedeomyia. In many larvae there are stout spines 

 at the angles of the thorax which prevent the long hairs from being bent back- 

 wards. 



There is wide diversity in the coloration of mosquito larvae. While certain 

 forms have a characteristic coloring there is often great variation in this respect ; 

 color, beyond the fact that certain genera show a characteristic coloring, can 

 not be used for identification. 



All the larvffi of the tribe Sabethini that we have seen have a characteristic 

 pale appearance. The body is opaque creamy white and the head and other 

 chitinous parts light yellow. Only the foramen of the head is more or less 

 broadly edged with black, and sometimes the anal plate also shows a dark 

 margin. The larvae of Megarhinus are dark and the integument shows a more or 



