BIORHIZA APTERA. 99 
Average dimensions of a mature specimen.—One larval 
cell: Height, 8mm.; girth, 30 mm. 
May be sought during any month of the year. 
Growth is complete by the end of October. 
The typical condition of the gall is unilocular and unilarval. 
The larva pupates in the gall. The imago emerges during the 
winter and the spring. 
Parasites, Nos. 15, 175. 
Alternate sexual generation: Teras terminalis, Fabr. 
“The time given:by different authorities for the 
appearance of the flies varies, some having found them 
in November and some in March; according to my 
own observations the latter date must be considered 
exceptional, at least in this place (Schleswig). I have 
for many years found the flies regularly in the end of 
December and beginning of January” (Adler, ‘ Alter- 
nating Generations,’ p. 71). 
This gall appears to have been well known in the 
south of England prior to the year 1874, But it had 
only been observed. on the roots of oak trees that had 
been blown down by gales, and not as the result of 
entomological research. It occurs on the subterranean 
roots only; on the largest and thickest, as well as on 
the most slender, but with greatest frequency on those 
varying in dimensions from that of a quill to that of a 
lead pencil. 
Tt is seldom solitary, but when so the size ranges 
from 5 mm. to about 15 mm. in diameter, and the 
shape is more or less globular. 
The general condition of growth is gregarious, and 
in conglomerated clusters of considerable numbers; 
the overcrowding in some masses being so great that 
distortion and fantastic shapes are the result. Some 
clusters resemble the gall of Aphilothrix radicis, but 
may be easily distinguished, from that species by (a) 
the outline of the cluster showing each separate larval 
chamber; (b) each larval chamber, although attached 
to those next it, may be separated without injury; or 
(c) by making a transverse section, when it will be 
