34 THE BLOWFuIES oF NortH AMERICA 
Measurements of the height and length of the head are taken 
in profile view. The length of the head at the antenna is the 
average length in micrometer units from the visible posterior 
margin of: the head (most often visible just behind the postocular 
cilia) to the.antennal base. The length of the head at the vibrissa 
is the average length in micrometer units from the. lower rear 
margin of. the metacephalon to the vibrissal angle. The height 
is the average distance i in micrometer units from the lowest mar- 
gin of the head to the upper ocelli. . The eye height is the distance 
in micrometer units from the lowest, point. to. the, uppermost, 
margin. 
The buccal height in relation to. the eye height is obtained 
by dividing the number of micrometer units in the height of 
the eye into the number of micrometer units in the height of 
the bueea (distance from the lower margin of the head to the 
lower eye margin). : 
The width of the front at the PSs in relation to the 
head width is the fraction obtained by dividing the number 
of micrometer units between the eyes across the inner vertical 
bristles by the number of micrometer units in the entire head 
width. The width of the front at the narrowest portion and at 
the lunule are obtained similarly. 
The width of the parafaciale is the distance from the margin 
of the eye to the slight angle where the parafaciale widens ‘to: 
meet the frontale, just above the first antennal segment and 
nearly at the lunule. The width between the vibrissae is the 
distanee between the bases of the largest bristles. 
The costal margin of the wing is divided into a series of 
sections by the terminations of the longitudinal veins, and the 
relative proportions of these sections to one another are expressed 
by the average number of micrometer units in: each section. 
In the Mesembrinellinae the character is of great value, but in 
the Luciliini and Calliphorini it is not so useful because of 
variation in specimens of what appear to be ‘the same: species. 
However, such figures do aid in indicating the eS of certain 
wing veins. 
The terminology applied. ‘i the leg bristles in. ‘thi: paper 1s 
that now in common use by. students of the taxonomy of the 
Anthomyiidae.. When rows of bristles occur regularly upon a 
certain leg surface, or when a. constant number of. bristles has 
been found in certain positions throughout the species of a 
genus, then this fact is noted in the generic description. When 
the number of bristles or the position of certain bristles upon a 
vxiven lee surface has been found to vary from one species to 
