25 
the emergence of the parasites. The maggots pupate close to the 
dead hosts, in the body of which they ordinarily produce a deep 
excavation, which is quite filled up by the puparium. In each 
host only one parasite develops. 
Actia pilipennis is at least double brooded. At Tisvilde the 
first brood was reared in May from Retinia resinella, and the flies 
then infested the caterpillars of R. buoliana, which at that time were 
almost fullgrown; from these the flies emerged in July and August. 
Fig. 
1 
2 
3 
dr 
5 
6 
Explanation of the figures in the text. 
(p- S me. of Carcelia gnava on a hair of Stilpnotia sacilis. 
(p. — on theskin o — 
(p i eres Snake 2 stage: Anterior ranes 
(p. — 3: 
(p. É, == 3. — Pesteriir apirasle 
(p.7) Egg of a not reared tachinid fly on a hair of Acronycta 
menyanthides. 
7 (p.7) The pharyngeal skeleton of a maggot taken out of the egg 
figured in fig. 3. 
8 (p8) Young caterpillar of Stilpnotia sacilis killed by Carcelia 
gnava and hanging down from a branch after the emergence 
the É 
9 (p. 10) Exorista Sænorkeee, Spines from the side of the mouth. 
10 (p.10)  — 3” stage. Anterior spiracle. 
11 (p. 11) Trachea of an Angels with a funnel of a maggot of 
Ewxorista blepharipoda. 
12 (p. 13) Meigenia floralis 3' stage. Anterior Den 
13 (p. 18) Åctia pilipennis 3. stage. Rows of spines. 
14 (P. 18) Actia seere Furcated spines from the dorsal side of 
the llth 8 
== eo 
”- 
15 (p. 18) Actia pilipennis g mage Pharyngeal skeleton. 
16 (p. 19) — Anterior åerne 
17 (p. 19) — 2 slå Sidewiev. 
18 (p19) — — — … Posterior spiracle (Only the out- 
pe of the border of the left spiracle have been drawn. 
. border. b. respiratory knob"). c. atrium. 
19 (p. 20) lå pilipennis Puparium. 
I have formerly described a similar spiracle from a maggot parasitic 
in a Lithobius. I supposed that the maggot belonged to Discochæla 
lithobii a species which Giard had founded on flies reared from a 
Lithobius. Now I think that this suggestion is highly probable, 
because the Discochæta is closely related to Actia pilipennis. 
