D4 
d. Oestriden, Vienna 1863, p.53—90). The ordinary species, 
the common gad-fly of the horse, Gastrophilus equi, occw's i 
nearly all the parts of the old world and has followed civili- 
sation into America and Australia. It is very probable that 
the ancients, ignorant as they were of the biology of Gastrophilus, 
and observing these flies swarm about horses, connected them 
with their notion about oxen-born bees, and as the honey-bee 
was already preoccupied by the ox, the brownish gad-fly was 
taken for a horse-born hornet. 
But as the hornet is a kind of wasp, it happened later 
that the oxen-born wasp of the ancients (which, as I have shown, 
p. 9 and 15, is the fly Helophilus) became confused with the horse- 
born hornet (the fly Gastrophilus), by people who spoke of them 
from mere hearsay, and not from actual observation. The ancients 
thus had: 
1. The oxen-born bee — Lristalis tenaz, 
2. The oxen-, or horse-born wasp — Helophilus, both pro- 
duced from rat-tailed larvae, occurring promiscuously in all kinds 
of stagnant and fetid waters; 
3. The horse-born hornet — Gastrophilus equi, imtimately 
connected with the horse, the larva living in its stomach, and 
therefore erroneously confused with the real carcase-born flies 
Evistalis and Helophilus. 
To this trio of real, or pretended, carcase-born insects, a 
fourth companion is often added by ancient authors, a beetle 
(scarabaeus) issuing from the carcase of an ass. So in Pliny 
(XI, 20): ,Virgilius juvencorum corpore exanimato. Sicut equo- 
rum vespas atque crabrones; sicut asinorum scarabaeos mutante 
natura ex aliis quaedam in alia.“ The same combination we 
meet in Plutarch (Cleomenes) and elsewhere. Modern authors 
have often referred to it; for instance Melanchthon in his 
allegory, reproduced below (in Supplem. VI), and Réaumur in 
the chapter which I have translated above, in my Supplement III. 
The beetle is probably the common black dung-beetle (Geotrupes), 
but what connection it has with a dead ass, I do not attempt 
to explain. 
