DIP TER A, 
419 
Cyclorrhapha with a frontal suture (SCHIZOPHORA) 
Normal Schizophora. 
The Thickhead-flies, Family ConopiDjE. p. 476. 
The Bot-flies, Family CEstriDjE. p. 477. 
The Muscids, Family MusciDiE. p. 479. 
The Pupa-bearing Flies (Pupipara). 
The Louse-flies, Family Hippoboscid^e. p. 487. 
The Bat-ticks, Family NycteribuDjE. p. 489. 
The Bee-louse, Family BRAULlDiE. p. 489. 
Classification of the Diptera. 
(For advanced students .) 
In the following table for determining the families of the Diptera 
use is made chiefly of characters based on the form of the head, an¬ 
tennae, and wings. 
The more important of the characters presented by the head are 
the presence or absence of the frontal lunule, and the presence or ab¬ 
sence of the frontal suture when the lunule is present. (See page 416, 
note.) In those families that possess the frontal suture there exists 
a large bladder-like organ, the ptilinum (ptil'i-num), which is pushed 
out through this suture when the adult is about to emerge from the 
puparium. In this way the head end of the puparium is forced off, 
making a large opening through which the adult escapes ; afterwards 
the ptilinum is withdrawn into the head. If a specimen is captured 
soon after its emergence from the puparium, there may be seen in¬ 
stead of the frontal suture the bladder-like ptilinum projecting from 
the head, immediately above the antennae. 
The form of the antennae is of prime importance in determining 
to what family a fly belongs. In the more generalized families the 
antenna consists of many segments, which, except the basal two, are 
similar in form (Fig. 487). Frequently such antennae bear whorls of 
long hairs (Fig. 488). In the more specialized families there is a re¬ 
duction in the number of segments of the antenna. This is brought 
about either by a more or less complete consolidation of the segments 
beyond the second into a single segment (Figs. 489 and 490), or by a 
dwindling of the terminal segments, so that they form merely a slen¬ 
der style (Fig. 491) or bristle (Fig. 492). Such a bristle is termed by 
many writers the arista (a-ris'ta). In most cases where a style or 
arista exists it is borne by the third segment, and this segment is then 
usually greatly enlarged. When the enlargement of this segment has 
taken place evenly the style or arista is terminal; but frequently one 
part of the third segment is expanded so that it projects beyond the 
