DIPTERA. — TACHYDROMIID&. 547 
But little is known of the preparatory states of these insects. M. 
Macquart, indeed, states that he once found a specimen of Empis 
opaca in the act of disengaging itself from the pupa skin, which he 
describes (Hist. Nat. Dipt. tom. i. p. 326.), and which closely resem- 
bles the pupa of Asilus: the front of the head had probably fallen 
off, as he does not describe any horns, which are so remarkable in 
‘Asilus. Bouché has observed the transformations of Ramphomyia 
spinipes (Naturgesch. pl. 4. f. 26—30.), the larva of which (fig. 129. 
5.) is a long apod grub, with the segments much constricted, and 
rather broader towards the hind part of the body, the last segment 
with two spiracles on the upper side, and with two long impressions 
on the under side. The pupa is incomplete, elongate-oval; it has a 
mucro at the end of each antenna-case, and four long bristles on the 
head: the segments of the abdomen are also furnished at the extremity 
with rows of bristles. The larva was found in garden vegetable 
mould. 
The TAcHypRoMIID# is a family of minute, very active insects, 
nearly allied to the Empidz (with which they are united by Latreille 
and Stephens), remarkable for the peculiar construction of the legs, 
and which have the antenne apparently only 2-jointed, with a 
long terminal seta (fig. 129. 7.): another basal joint, however, exists, 
but it is very small. The proboscis is generally short, and the palpi 
are incumbent (fig. 129. 6. head cf Tachydromia). The wings have 
not the large cell beyond the middle (fig. 129. 8. wing of Tach. 
arrogans); they are often ornamented with coloured fascize. The 
fore legs in the genus Hemerodromia are raptorial, having the coxe 
very much elongated, and the femora thickened and spined (fig. 129. 
9.): the latter character, in the first or second pair of legs, also 
occurs in the genus Tachydromia. The latter generic name is very 
characteristic of the habits of the typical species, which run with 
wonderful quickness, with their wings lying flat on the back, espe- 
cially on the trunks of trees ; others are found amongst herbage. 
There has been so much confusion in the employment of the 
generic name Sicus (first proposed by Scopoli for the insects which 
Fabricius afterwards called Myopa; subsequently, in 1796, used 
by Latreille for the typical genus of the present family, afterwards 
called Tachydromia by Meigen; then, in 1798, given by Fabricius 
to the genus afterwards named Cenomyia by Latreille; and, lastly, 
NN 2 
