No. XV.—DIPTERA: HETERONEURIDA, ORTALIDA, TRYPETIDA, 
SEPSIDA, MICROPEZIDA, DROSOPHILIDA, GEOMYZIDA, MILICHID Ai. 
By C. G. Lamp, M.A., B.Se., Clare College, Cambridge. 
(CoMMUNICATED BY PROFESSOR J. STANLEY Garpiner, M.A., F.R.S., F.LS.) 
(Plates 19—21 and 48 Text-figures.) . 
Read 4th March, 1914. 
THIS paper concludes the description of the Acalyptrate muscids of the Seychelles 
expedition. Among the families treated of there are several forms which, in the rather 
fluid state of the classification, must be regarded as possibly needing relegation to other 
or even to new groupings when the world forms are more fully known. Hence it has 
been thought desirable to refer fairly fully to the chetotaxy even in individuals which 
are placed in genera already founded. To save space the following abbreviations are 
used : 
f. 0. fronto-orbital bristles. prescut. prescutellar bristles. 
1. v. inner vertical bristles. p. a. post-alar bristles. 
o. v. outer vertical bristles. s. a. supra-alar bristles. 
p. v. post-vertical bristles. i.a. intra-alar bristles. 
oc. ocellar bristles. st. p. sternopleural bristles. 
post orb. the row of post-orbital bristles. mesopl. mesopleural bristles. 
d.c. dorso-central bristles. acr. the acrostichal row. 
h. humeral bristles. div. divergent. 
n. p. the two notopleural bristles. conv. convergent. 
presut. presutural bristles. 
In describing the head a systematic method has been adopted: the insect is 
adjusted in the field of the binocular microscope by means of a gimbal-like stand which 
enables all possible rotations and translations to be made. It is first adjusted to view 
the vertex perpendicularly, this is called the Top View; it is then twisted about to 
view the face perpendicularly, and this is called the Front View; finally it is adjusted to 
look at the side of the head, and this is the Side View. ‘These views correspond to the 
Plan and Elevations of the engineer's drawings. The structures seen in each view are 
then described in detail and in order. This method obviates the troublesome process of 
continually shifting the position of the insect when comparing it with a given 
description. 
SECOND SERIES—ZOOLOGY, VOL. XVI. 40 

