64 ILLINOIS BIOLOGICAL MONOGRAPHS [234 



EXPLANATION OF PLATE 



Cephalic Aspect of the Head and Mouth-parts 



Hypothetical head. 

 Simulium vcnustum, female. 

 Siniuliuui johannseni, male. 

 Bibioccphala elegantula, male. 

 Bibiocephala elegantula, female. 

 Rhabdophaga strobiloides. 

 Mycetobia divergens. 

 Psychoda albipennis. 

 Rhyphus punctatus. 

 Psorophora ciliata, female. 

 Mycetophila punctata, female. 

 Chironomus ferrugineovittatus, female. 

 Bibio femoratns, male. 

 Bibio femoratus, female. 

 Ptychoptcra rufocincta. 

 Trichocera bimacula. 

 Sciara varians. 

 Tipula bicomis. 



