72 
ample, 0 to 389 per square yard in Liverpool Lake and 0 to 128 per 
square yard in Thompson Lake in the same period. 
While two of the formerly common clean-water midges, Chironomus 
ferrugineovittatus Zett. and Procladius concinnus Coq. were still common 
in the lake in 1920 and, along with a new entrant, also at least not of 
pollutional habit, made up the bulk of the large increase in Chironomidae 
in collections in this lake since 1915, the full list of species for 1920 is 
much smaller than formerly, and calls attention to several species, some 
of which are partial to cleaner bottom, that have dropped out since the 
earlier period. 
Though separate collections of the small weed-animals were not 
taken in 19183—1915 in Stewart Lake, as in Thompson Lake and others 
just north of Havana, it is well enough known to us from general ob- 
servations that there was a rich fauna of that kind here in those years. 
Since much the richest portion of the old weed-fauna areas in the Illinois 
valley lakes was found in the Potamogeton or Ceratophyllum associa- 
tions, and the poorest in the Nymphaea and Nelumbo beds, and as 
Stewart Lake lost a very much larger proportionate amount of its Pota- 
mogeton and Ceratophyllum than of its lilies in the five years preceding 
1920, it is plain that the loss in the small weed-fauna of the lake has been 
very large in the period, though smaller than in the lakes twenty miles 
north. 
A table recapitulating all our 1920 distributional data on the larval 
midges from the river and lakes between Chillicothe and Browning fol- 
lows the short lists of species from Stewart Lake next presented, and 
with them concludes the present section. 
Mince LARVAE (CHIRONOMIDAE) oF Borrom Mups, 
Srewart Laker, 1913—1914 To 1920 
1. Oleaner-water species or other species present in 1913—1915 that have 
dropped out since then. 
Palpomyia species, 9 mm. 
Tanypus monilis L. 
Procladius culiciformis Lw. 
Tanypus dyari Coq. 
Chironomus lobiferus Say. 
2. .Cleaner-water species new to the lake since 1913. 
Palpomyia longipennis Lw. Common, 1920. 
8. Cleaner-water species common both 1913—1914 and 1920. 
Procladius concinnus Coq. 
Chironomus ferrugineovittatus Zett. 
