60 
ponds, and I made them develop in tubs of water which had 
no bad smell.“ 
I have quoted (p. 86) an instance from New Zealand, at a 
wool-scouring etablishment, where hundreds of larvae of Hristalis 
tenax were observed swimming in fat-barrels, some of which 
had been standing for two years and were filled ,with a thick, 
black, strong-smelling liquid; the larvae however appeared to 
thrive very well in this atrocious stuff.“ 
Finally, we have a dozen of well-authenticated instances of 
larvae of LHristalis developing within the human intestines. The best 
report of such a case was published by Dr. Balthasar Wagner 
in Fulda (Stett. Entom. Z. 1870, p. 73—80), when 3—5 larvae 
were voided, and from one of them Fristalis arbustorum was 
actually reared (1). It has not been ascertained yet how these 
larvae get into the human body. It seems probable however 
that they are swallowed, in the early stage of their develop- 
ment, with drinking-water. But it is nevertheless astonishing 
that they can reach maturity under such, for them extraordi- 
nary, circumstances. 
I have given instances enough to show that rat-tailed 
larvae are not very fastidious in the choice of a medium for 
their development. They would certainly not object to pools of 
putrid liquid under carcases of animals, if opportunities were 
ottered to them, Experiments might be tried, but in the matter 
of such experiments it should be borne in mind that they are 
conclusive only in case of success; a failure proves nothing, 
because we can never be sure of having fulfilled all the condi- 
tions required in nature. But instances may probably be met 
(1) Other cases are reported by Spangenberg, Ent. Tidskr, Stockh. 1886, 
p. 121, in America by Prof. Riley, Proc. Ent. Soc. Wash. I, 4, p. 264 (1890); by 
J. A. Lintner, State Entomologist in Albany, N. Y. (im litt. to me), a case with 
a colored woman. 
Hagen’s Bibl. Ent. refers to: J. Jacob d’Annone, Acta Helv. 1760, T. IV, 
p. 801 —306, Tab. I. I saw this paper in Prof. Westwood’s library in Oxford. 
A woman, with great pain, voided a rat-tailed larva. 
