$99 -- Ture BLOWFLIES oF NortH AMERICA 
laterally; ventrally on posterior margins of all but segments 
5 and 6 with a few rows of spines. No development of swollen 
spinose pads which occur on under surface of most ealliphorid 
larvae. Anterior spiracles laterally near posterior border of 
second segment, each with four apertures. Posterior spiracles 
in weak posterior depression, separated by one and one-half 
times the spiracular length, each circular in outline, bulging very 
slightly at ‘‘button,’’ which is above a median line; peritreme 
not continuing around ‘‘button,’’ which does not cause a gap 
in peritreme and is not enclosed by the peritreme; each spiracle 
with three short, wide, nearly straight, well-separated slit-like 
apertures which converge toward the ‘‘button.’’ Three pairs of 
tubercles on anterior margin of posterior depression and two 
pairs on lower margin, with another pair below the latter. 
Cephaloskeleton mainly as in the previous instar; ventral sur- 
face of ventral cornua smooth; labial sclerites larger and more 
heavily sclerotized than in previous instar. This instar requires 
about eleven days and this time may or may not be spent within 
the host. Third instar larvae readily feed upon dead material, 
while those of the earlier instars apparently are unable to do so. 
Puparium. With the major external characters of the third 
instar larva. The prepupal stage requires from three to four 
days, and the pupal period lasts about twelve days in the soil. 
The larvae are deposited in the soil. The means of entry of 
the larvae into the host has not been determined. The first instar 
larva may be found beneath the skin of the host and parasitized 
earthworms may be easily recognized by constrictions of the 
skin along the ‘‘tracks made by the larvae crawling under the 
skin, the larvae traveling around the worm in a spiral path and 
moving toward either end.’’ The third instar larva enters the 
body cavity of the host and it completes its development as a 
parasite, or, if the earthworm dies, it feeds saprophagously. 
Onesia bisetosa, new species 
Onesia agilis Shannon (nee Meigen), Insecutor Inscitiae Men- 
struus 11:108, 1923. - | | ) 
Onesia sp. Séguy, Encyel. Ent. (B II.) Dipt. 2:86, 1925. 
Séguy was correct in his assumption that Shannon’s agilis is 
different from agilis Meigen. Superficially, the species resembles 
biseta Vill. and will run to that species in the keys of Stein 
(1924) and Séeguy (1928), as do specimens determined as agilis 
by Villeneuve, Stein, and Séguy, now in the National Collection. 
The North American form differs most obviously from the Euro- 
