293 



topogon, Culicoidcs, or Forciponiyia. The probability is that a large 

 number of species belonging to these genera occur in Illinois, but their 

 small size, coupled with the difficulty in preserving and identifying 

 them, deters most entomologists from collecting them, and with only 

 the material recently collected by Mr. Hart and myself before me I 

 do not consider it advisable to attempt making keys to these genera that 

 might serve for the identification of all the described North American 

 species. 



Keys to Genera 



LARV.^ 



All segments Avith distinct bristles ; pseudopods present 



Ceratopogon tmd Forciponiyia. 



All segments without bristles ; pseudopods absent 



Culicoides, and Palpomyia, sens. lat. 



FJJPJE 



Thorax and abdomen with distinct bristles or spines 



Culicoides, Ceratopogon, and Forciponiyia. 



Thorax without any spines, abdomen with tuberculate or leaflike 



protuberances on segments Palpomyia, sens. lat. 



IMAGINES 



1. Wings with distinct surface hairs, either in the form of short, up- 



right microscopic setulfe or as broad decumbent scales 2 



— Wings bare 5 



2. Thorax with a distinct slitlike or circular depression on each side of 



disc slightly posterior to the inner extremity of prescutum 



Culicoides (p. 295) . 



— Thorax without these depressions 3 



3. Wings with distinct decumbent scales on entire surface 4 



— Wings with short, upright setulose hairs which are usually confined 



to apical half; empodium large Ceratopogon (p. 304). 



4. Hairs on wings rather sparse, basal joint of hind tarsus twice the 



length of second ; apical 4 antennal joints of male elongated and, 

 except the last one, binoclose Pseudoculicoides (p. 309). 



— Hairs on wings very dense, particularly in females ; basal joint of 



hind tarsus not, or very slightly, longer than second ; apical 3-4 



antennal joints of male elongated, not binodose 



Forciponiyia (p. 311). 



5. First and third veins connected by a cross vein or fused basally. . .6 



— First and third veins disconnected for their entire length 10 



6. At least one pair of femora with distinct ventral spines 7 



— Femora without ventral spines 9 



