244 



Mycetobia Meigen 



I have before me all stages of the only described North American 

 species of this genus. The early stages have been previouslv described 

 by Johannsen and myself, and the figures given herewith are merely 

 supplementary to these descriptions, references to which are given in 

 the synonymy of the species. 



MycET'OBIA diveRGEns Walker 



Mycetohia divergens Walker, Iiis. Saiind., Dipt., Pt. 1, p. 418. Imago. (ISDe) 

 Mycetophila persicae Eiley, Prairie Fanner, June 15, 1867, Vol. 35 (n. s., 5), 



No. 19, p. 397. Imago. 

 Mycetohia sordida Packard, Guide to the Study of Insects, p. 388. Imago. (1869) 

 Mycetohia marginalis Adams, Kans. Univ. Sci. Bull., Vol. 2, No. 2, p. 21. Imago. 



(1903) 

 Mycetobia divergens Walker, Johannsen, Bull. 172, Maine Agr. Exper. Station, 



p. 223. Larva, pupa, and imago. (1910) 

 Mycetohia divergens Walker, Malloch, Bull. 111. State Lab. Nat. Hist., Vol. 11, 



Art. 4, p. 321. Larva and pupa. (1915) 



Larva (PI. XXXVI, Fig. 3). — Length, 11-13 mm., diameter, 

 .60 mm. White, semitransparent, thoracic segments marked with vel- 

 lowish brown. 



The principal distinguishing features of this species as compared 

 with Rhyplms, apart from the difference in color and shape of the 

 apical segment, mentioned in key, are the more slender build of the 

 body and the dissimilar structure of the head. The greatest difference 

 is apparent in the form of the labial plate and mandibles, as shown in 

 Figure II, the mandibles in the present species being, pointed, and 

 armed on the upper margin with several teeth, while the labium is 

 tiot centrally incised. 



Pupa. — The principal differences between the two genera are em- 

 phasized in the key to pupae, and a comparison of Figures 8 and 9, 

 Plate XXXVI, will show the general build of the cephalic, thoracic, 

 and basal abdominal regions, as well as the armature of the latter, in 

 which there are decided differences. The ventral aspect of the head, 

 thorax, and base of abdomen is shown in Figure 6; the dorsal aspect 

 of head and thorax in Figure 7. 



The larvae of this species are very commonly met with in wounds 

 on trees from which sap is exuding. They feed upon the sap or the 

 fungus occurring in such situations, and the pupae are found among 

 the loose bark, especially where it is damp. The imagines behave in 



