72 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[242 



EXPLANATION OF PLATE 



Caudal Aspect of the Head 



Hypothetical head. 



Tabanus gigantens, female. 



Tabanus giganteus, male. 



Bibiocephala elegantula, male. 



Simulium venustum, female. 



Trichocera bimacula. 



Dixa clavata. 



Rhyphus punctatus. 



Sciara varians. 



Psychoda albipennis. 



Bibiocephala elegantula, female. 



Promachus vertebratus. 



Bittacomorpha clavipes. 



Rhabdophaga strobiloides. 



Mycetophila punctata. 



Chirono inus ferrugineovittatus. 



Chironomus ferrugineovittatus, dorsal aspect. 



Mycetobia divergens. 



