70 



MISC. PUBLICATION 336, U. S. DEPT. OF AGRICULTURE 



7. Spiracular bristles present; base of subcostal vein with a tuft of hairs 



on under side of wing Theobaldia 



Spiracular bristles absent ; hairs absent on under side of subcostal veiu_ 



8. Wing scales broad, mixed brown and white ; setae absent at base of 



vein 1 



Outstanding wing scales narrow or only slightly broadened, dark ; a few 

 setae near base of vein 1 on upper side of wing 



9. Fourth segment of fore tarsi very short ; lower mesepimeral 



bristles absent; mesonotum with longitudinal lines of white 

 scales Orthopodomyia 



Fourth segment of fore tarsi normal; lower mesepimeral bristles pres- 

 ent; mesonotum without lines of white scales Mansonia 



10. Antennae not longer than proboscis, the first flagellar segment of nor- 

 mal length; male with bushy antennae and long palpi (in United 

 States species) Culex 



Antennae much longer than proboscis, the first flagellar segment as 

 long as several of succeeding segments; male antennae and palpi 

 similar to those of female Deinocerites 



10 



KEY TO LARVAE (Fourth-Stage) 



The genera are separated in couplets 1 to 9, 

 couplets that follow. Air-tube lengths, when 



l/jojyer /?ea</ Aa/r 

 Lower /?eac/ /?a/r 



z^/77 l -e/7/7a/ Aa/r' 



jLarfera/ Aa/'r 

 Su6c/orsa/ /?cr/r- 



Aa/era/ co/776 

 or&™ tSeysnenr 



s4/7cr/ sey/?7e/7r- 

 J^/7 fra/ 6rus/? - 



s4/?a/ j///,? 



/?orsa/ fa/? 



Figure 20. — Larva of Culex quinquefasciatus with 

 the parts named. (Howard, Dyar, and Knab) 



^4/r fv6e 



Pecfe/7 



and the species in the 

 mentioned in connec- 

 tion with the species, 

 are given in multiples 

 of the diameter of the 

 base of the tube. 

 Mounted larval skins 

 become flattened by 

 pressure of the cover 

 glass, and allowance 

 must be made for this 

 in estimating the pro- 

 portions of the tube. 

 Variations may occur 

 in the number of 

 branches as given for 

 certain hairs ; that is, a 

 normally double hair 

 may occasionally be 

 single or triple, or a 

 single hair double. In 

 examining flattened 

 specimens care must be 

 taken to distinguish 

 between the upper and 

 lower surfaces of the 

 body. The terminol- 

 ogy of the larval parts 

 is shown in figures 20, 

 21. and 22, 



