872 THE AMERICAN NATURALIST. (VoL. XXXIX. 
is present in its central cell. It is easily recognized, not only 
by its larger size, but especially by the presence of the ‘breast 
bone" so characteristic of all Cecidomyiid larvae. Larve of 
small Cecidomyidz are found in considerable numbers between 
the outer scales of many galls. These are also recognized by 
the * breast bone" but with 
greater difficulty because of 
their smaller size. 
Twenty-three 1904 pubes- 
cent galls from the region of 
Pettibone Creek, north of 
Lake Bluff, Ill., gathered and 
examined in October, 1904, 
contained fifteen living and 
two dead larve of the gall 
gnat which produces the gall 
(6 galls were without Rhab- 
dophaga larva), 169 small 
Cecidomyiid guest larva, 6 
larvae of Hymenopterous para- 
sites of which two were in the 
central cell of one gall in place 
of the Rhabdophaga larva, 
and 384 meadow grasshopper 
eggs. One 1903 gall from the 
same place contained 16 grass- 
hopper eggs. 
© Nine I904 pubescent galls 
larva in a burrow; e, eggs of Xiphidium ensife- from South Wayne, Wis., 
rum; f, larva of Hymenopterous parasite. gathered December 26, 1904, 
contained 9 larve of gall 
gnats, I guest Cecidomyiid about half as long as the gall maker, 
37 smaller Cecidomyiid larva, 2 parasitic larvae, and 13 grass- 
hopper eggs. Six 1903 galls from same place contained 32 
grasshopper eggs. 
Seventeen 1904 crooked-stem galls from west of Lake Bluff 
Ill, gathered January 17, 1905, contained ten larvz of the gall 
maker, 28 Cecidomyiid larvae about half as large as maker, 10 


