occur in the National Museum collection, and (h) the unrecognized 

 forms, which are known only from the literature: (III) a synoptic con- 

 sideration of the species of the genus Culex, divided into (c) a table of 

 the recognized species, and (h) an account of the unrecognized species; 

 (IV) a brief description of the only valid known species of the genus 

 Psorophora; (V) a synoptic table of the three known species of the 

 genus Megarhinus; and (VI) a synoptic consideration of tlie two known 

 species of the genus Aedes. 



So far in the medical literature oidy the genera Anopheles and 

 Culex have received consideration, but since this circular is intended 

 simply to aid in the identitication of the different forms, the other 

 three jjfenera have been added in order to avoid confusion. 



Pig. 3. — Resting positions of Culex (at left) and Anopheles (at right) , enlargeil (redrawn from a rough 

 sketch published in the British Medical Journal i . 



The tigures which are given illustrate the structural points brought 

 out in the synoptic tables and have been drawn by Miss Sullivan, 

 of this office, under Mr. Coquillett's supervision. The figure repre- 

 senting the difference in the resting positions of Anopheles and C*ulex 

 has been redrawn from a sketch made l)y a member of Ross's expedi- 

 tion to Sierra Leone. Neither the writer nor Mr. Coquillett is able 

 to verify the suggestion that either of these insects uniformly rests in 

 the positions indicated, although it is quite likely that the attitudes 

 shown are the usual ones. 



Respectfully submitted. 



L. (). Howard, 



Kntoinol<MJix.t. 

 Approved: 



James Wilson, 



Secretary of Aqriculture. 

 Washington, D. C, February W, 1900. 



