446 



27- Chiroxomus ferrugineovittatus Zetterstedt 



(Plate XXXII, Fig. 10) 

 Chironomus ferrugineovittatus Zetterstedt, Dipt. Seand., Vol. 9, 1850, p. 3492. 



Larva. — Length, 45-60 mm. Blood-red. Ventral respiratory or- 

 gans absent. For full description see an earlier article by the present 

 writer*. 



Pupa. — Length, 17-19 mm. Red, becoming yellowish before 

 emergence of the adult. 



Frontal tubercles of moderate size, slightly curved downward at 

 apices. Thoracic respiratory organs terminating in numerous white, 

 hairlike filaments ; disc with a brown median line and another line of 

 same color on each side above the portions occupied by vittse of the en- 

 closed imago, the surface not setulose but with about six weak hairs. 

 Abdominal segments with a brown line on each side which is dilated at 

 anterior extremity ; disc of segments covered with very minute closely 

 placed setulae which almost cover their dorsal surface and are slightly 

 longer posteriorly; surface hairs inconspicuous, one on each side of the 

 median line near posterior margin much stronger than the others; 

 apical lateral organ of eighth segment similar to that of decorus, and 

 with the apical abdominal appendages mostly deep brown. 



Imago; Male. — Differs from plnmosus in having the vittse and the 

 dark marks on the basal four segments of abdomen usually bright fer- 

 ruginous, the apical segment of the latter usually of the same color and 

 the intervening segments gray or blackish. 



Structurally the two species are very much alike, the principal dif- 

 ference being that the legs in ferrugineovittatus are noticeably thicker 

 than in plnmosus and the superior process of hypopygium much more 

 slender. The proportions of fore tibiae and basal 3 joints of fore tarsi 

 are 105, 128, 70, 40. Hypopygium as in Figure 4, Plate XXXIIL 



Female. — Similar to that of plnmosus; differing in having the vit- 

 tae paler and the legs thicker. 



Length, 12-13 ^"^• 



Illinois locality, Havana. Abundant everywhere from the middle 

 of April through a good part of May, also occurring in September in 

 the imago stage. Larvae occur throughout the year in the various 

 lakes connected with the Illinois River at and near Havana and in some 

 parts of the channel of the river. The writer was not successful in 

 rearing the imago. Cast pupal skins were found in immense numbers 

 along the shore of the Illinois River and floating on the surface of the 



*Bull. 111. state Lab. Nat. Hist., Vol. 10, Art. 4, p. 215. 1914. 



