354 
Parasites of Common Flies 
In 1917 and 1918 infected specimens of II. dentipes were found in July and 
the disease was first noticed in M. domestica on September 13, 1917, and on 
July 25, 1918. In H. dentipes the symptoms develop with very great rapidity. 
For example an apparently normal specimen caught in the morning was dead 
and showed well marked rings round the abdomen by 6.30 in the evening. 
After a certain period a halo of spores is thrown out round the body. 
As previously suggested (1916, p. 507) the infection may spread from such 
flies as H. dentipes, which develop the disease in the middle of summer, to 
M, domestica or its larvae. 
In 1916 infected specimens of Lucilia were found outside on July 7 and 
August 22 (PL XIX, fig. 4) and in 1917 a specimen on July 2. 
In 1917 six infected specimens of F. canicularis were found indoors on 
October 1 and 7 and November 9 and 14. 
On August 13, 1917, an infected specimen of an A. radicum was found on a 
window. 
On August 3, 1916, an epidemic commenced amongst 28 specimens of 
S. carnaria kept in a cage out of doors. Thirteen of the flies died with very 
well marked signs of the disease on August 3, nine on August 4, and two on 
each of the three succeeding days. 
On August 7 seven wild specimens were caught and placed in the cage. 
All died of the disease, one on August 9, one on August 10, and five on 
August 14. Spores were thrown off in the form of a halo round the dead flies 
(PL XIX, fig. 5). Subsequently wild flies of several species were put into this 
cage, but did not develop the disease. S. carnaria therefore seems to be ex¬ 
tremely susceptible when exposed to the disease, but the infection of this 
species has never been recorded previously. 
DESCRIPTION OF PLATE XIX. 
Fig. 1. Blow fly ( C. erythrocephala) with a large drop of fluid (“vomit”) which had been re¬ 
gurgitated adhering to its proboscis. The drop was subsequently withdrawn. Nat. size. 
Fig. 2. M . stabulans, sitting on the top of a wall, with a drop of dark coloured, regurgitated fluid 
adhering to its proboscis. Nat. size. 
Fig. 3. Fly with numerous hypopial nymphs adhering to its thorax and head, x 5. 
Fig. 4. A specimen of L. caesar dead of empusa disease adhering to an artichoke leaf. Nat. size. 
Fig. 5. Specimen of S. carnaria dead of empusa disease, surrounded by a halo of spores. Nat. 
size. 
Fig. 6. A. manducator ovipositing in a larva of C. erythrocephala. Nat. size. 
Fig. 7. A Figitid emerging from a puparium. x 5. 
Fig. 8. Cork of a test-tube in which several specimens of M. acasta were confined. Two grooves 
gnawed by the females are shown (see p. 363). Nat. size. 
Fig. 9. Puparia from which A. cephalotes emerged (upper row), and from which Figitids emerged 
(lower row). Nat. size. 
Fig, 10. Puparium opened longitudinally showing living nymphs of M. acasta (see p. 363). x 4. 
Figs. 11, 12. A Proctotrupid ( Trichopria , sp.) male and female, x 8. 
, Figs. 13, 14. M. acasta, male and female, x 10. 
