TACHINID PARASITES OF THE GIPSY MOTH. 
209 
P. hyalinus was thus peculiarly an enemy of fall webworm parasites, 
and thus a friend of the fall webworm. Neither, when it was present 
(which it was not, as a rule) , was it ever known to emerge from infested 
puparia of the "summer issuing species" until long after the flies 
had ceased to emerge. From the puparia of species which hiber- 
nated as pupae it never emerged until the spring and then appeared 
before the flies themselves. It was thus possible to provide against 
its escape with little trouble, and it is now considered as distinctly 
less menacing than the species which follows. 
Melittobia acasta Walk. 
Another most extraordinary parasite of tachinids in Europe is 
Melittobia aca sta, according to a determination furnished some years 
ago by Dr. Ashmead. It is thought probable that a careful com- 
parison between the parasite of the tachinids and If. acasta will 
reveal specific difTerences, but at the time of wrii ing such comparison 
has not been made. Of all of the secondaries which have been 
imported with the parasite material this has proved tin 4 most 
annoying. 
Its most annoying characteristic its minuteness, which enables 
it to pass through 50-mesh wire screen at will, and this, coupled with 
an extreme hardiness and an insidious inquisitiveness which seems 
to know no bounds, has resulted upon two occasions in an infestation 
of the laboratory which is comparable to a similar infestation, which 
will receive further mention, by the mite Pediculoides. 
No one knows where it came from upon either occasion or how it 
first succeeded in gaining a foothold in the laboratory. Its first 
appearance was in 1006, when Mr. Tims encountered it in several 
lots of puparia of different species of tachinids from several Kuropean 
localities. Mr. Titus evidently thought, judging from his notes, 
that it had been imported in each instance with the material from 
those localities. lie studied its habits that first year, and found 
that it would oviposit freely in confinement and that such oviposit ion 
was successful. He did not give it full credit for its insidiousness, and 
as a result it succeeded in eluding his vigilance and gaining access 
to a number of the lots of hibernating puparia of Blepharipa, upon 
which it reproduced with great freedom. 
In the spring of 1907 this circumstance became evident through 
its emergence in some numbers from several of the lots of hibernating 
puparia early in June, after most of the flies had issued. An examina- 
tion of the remaining puparia was thereupon undertaken and a vast 
number of larvae, pupae, and unissued adults destroyed. 
At that time it was supposed that each of the lots of puparia were 
infested at the time of their receipt, but when an even larger amount 
\)50T7°— Bull. 1)1—11 14 
