260 Prof. L. C. Miall and Mr. T. H. Taylor on the 
by the radula of a pond-snail among the microscopic alge 
of an aquarium. About the end of March the larva is 
full fed, and turns to a pupa, which, unlike that of many 
other leaf-miners, remains within the leaf. The flies 
appear about the end of May, and may be seen throughout 
ex A 
Transverse section of midrib of holly-leaf showing larval mine in central vein. (x 50.) 
June on infected holly-trees, usually alighting on the 
young green shoots. We have not met with them except 
on the holly, nor have we seen them fly except from one 
leaf to another. 
II. THE STRUCTURE OF THE LARVA. 
We shall begin by describing the larva in its first stage, 
and then notice the points of difference which mark the 
full-grown larva. 
The Exoskeleton. The body (fig. 2) consists of a head 
succeeded by three thoracic and nine abdominal segments, 
the two last of which are distinguished with difficulty.* 
Transverse bands of minute hooks make the junctions of 
the segments obvious, except where the 11th and 12th 
segments meet. The first band is restricted to the dorsal 
surface; the second is interrupted laterally; all the bands 
are interrupted along the mid-dorsal and mid-ventral 
lines. 
* Twelve is the usual number of post-cephalic segments in Muscid 
and Nemoceran larve. In one species of Chironomus we have found 
faint indications of a subdivision of the 12th larval segment, the 
part behind the bunches of sete being constricted off. 
