25 
the emergence of the parasites. The maggots pupate close to the 
dead hosts, in the bodj 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. 
Explanation of the figures in the text. 
Fig. 1 (p. 2) Egg of Carcelia gnava on a hair of Stilpnotia sacilis. 
— 2 (p. 2) — — — on the skin of — — 
— 3 (p. 4) Carcelia gnava 2’ stage. Anterior spiracle. 
— 4 (p. 4) — — 3’ — — — 
— 5 (p. 4) — • — 3. — Posterior spiracles. 
— 6 (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 lp 8) Young Caterpillar of Stilpnotia sacilis killed by Carcelia 
gnava and hanging down from a branch after the emergence 
of the parasite. 
Fig. 9 (p. 10) Exorista blepharipoda. Spines from the side of the mouth. 
— 10 (p. 10) — — 3’ stage. Anterior spiracle. 
— 11 (p. 11) Trachea of an Acronycta with a funnel of a maggot of 
Exorista blepharipoda. 
— 12 (p. 13) Meigenia floralis 3’ stage. Anterior spiracle. 
— 13 (p. 18) Actia pilipennis 3. stage. Rows of spines. 
— 14 (p. 18) Actia pilipennis. Eurcated spines from the dorsal side of 
the llth segment. 
— 15 (p. 18) Actia pilipennis 3’ stage. Pharyngeal skeleton. 
— 16' (p. 19) — — — Anterior spiracle. 
— 17 (p. 19) — — — — Sidewiev. 
— 18 (p. 19) — — — Posterior spiracle (Only the out- 
lines of the border of the left spiracle have been drawn. 
a. border, b. respiratory knob 1 ), c. atrium. 
-- 19 (p. 20) Actia pilipennis Puparium. 
J ) I have formerly described a similar spiracle from a maggot parasitic 
in a Lithobius. I supposed that the maggot belonged to Discochæia 
lithobii a species which Gi ard had founded on flies reared from a 
Lithobius. Now I think that this suggestion is highly probable, 
because the Discochæia is closely related to Actia pilipennis. 
