FAM. EMPIDIDZE 9 
prey continuously, methodically inserting the proboscis in various places, but after a few minutes, 
dependent upon the size of the prey, she terminates the copulation, drops the prey, cleans her pro- 
boscis, and the two fly away. 
The male of Emjpis aerobatica uses a small midge as a nucleus about which it fashions a large frothy 
balloon. Flying with this structure between its hind legs it attracts a female who alights on the back of 
her selected mate. The two then settle slowly to the ground, and after copulation has been completed 
discard the balloon. Some of the European species of Hilara have developed almost exactly the same 
method of balloon construction during courtship. In these cases it is the balloon rather than the 
original midge about which it was constructed that furnishes the stimulus for sexual selection because 
sometimes the minute insect is omitted. Balloons that have been dropped, probably after pairing, are 
utilized again by other males. 
The appearance of so specialized a habit as balloon construction in Emjisin America and in 
Hilara in Europe might suggest phyletic significance. [It is more plausible, however, to regard the 
habit as a simultaneous outgrowth from the general habit of offering prey for sexual selection, the result 
of the ability to blow viscous bubbles. 
TABLE OF THE SUBFAMILIES OF THE EMPIDID/E 
1. Discal cell always united. with the second basal, three posterior cells, anal cell 
and the anal vein wanting ov incomplete, auxiliary vein always vestigial and 
imperfect ov wanting, third vein always simple, basal cells often large, alula 
"absent, anal angle reduced, costa stopping at the fourth vein, usually no 
stigma; antenne two- or three-jointed, with a long leyminal or subdorsal 
two-jointed arista; proboscis short, vertical or inflexed, albi one-jointed, 
more ov less incumbent on the proboscis and oflen broad; pleure bave 
of hairs; bygidium asymmetrical, the uppermost valve unpaired ; coxe 
not elongate, femora often thickened and mucronate beneath; calypteres 
closely uniled to the base of the wing and with a small fringe; cursorial, 
RHSIHOl SÓEMIS, oe D iom SQUE Lom eiu mes v 9abfam. TACHYDROMIINA. 
Anal cell and. discal cell complete, or if either is incomplete the front. coxe ave 
greally lengthened and. the. front legs ave vaptorial or else the anal angle of 
the sing is rectangular, intercalary vein usually Present thus making four 
posterior cells, auxiliary vein more ov less distinct, third vein oflen furcate; 
proboscis oflen lengthened and palpi oflen porrect; bygidium with. paired 
HDIETUNDESCOADEDPUN ELvboOS; der e ue CORSI UN. TUI EU. 2 
2. Anal angle of the wing mot projecting, the outline of the wing move or less 
cuneiform, costa continuing around the hind margin of the wing, anal 
crossvein acule, perpendicular or rounded, very varely forming an obtuse 
angle, sometimes wanting, usually no fold in the wing under the humeral 
crossvein, no alula, calypleres closely united to the base of the wing, with 
a siraight edge and with a small fringe; proboscis short, mever longer 
than the head, either thick and fleshy ov sharp and incurved; arista or 
style terminal; eyes broadly separated on the front, oflem pubescent, ihe 
face narrower than the front; thorax elongate, mot highly arched, not 
pubescent, mesopleure obliquely longer tham vertically high; front coxe 
always longer than the posterior ones, mo afical libial spurs, empodium 
usually quite distinct although small; gressorial species... 0. 02 020. 02 020. 02 0. s 4 3. 
