198 
numerous around the vessels and along the inner surface of the 
wall, whicli is, of course, not lined by epitlielium. 
No trace of matter is seen in the tumor and also the excre- 
ments and cast larval skins of the parasites are removed from it. 
The food of the parasite con- 
sists of the biood of the tissues 
along the inner surface of the 
tumor. As will be shown fur- 
ther on, the mouth of the mag- 
gots is provided with spines 
especially adapted to irritate 
the tissues, and to form chan- 
nels along which the biood runs 
into the mouth opening. 
II. 
By an examination of the 
skin of the nestlings of Mimus 
modulator I succeded in tinding, 
besides numerous fully grown 
larvæ, also some younger ones 
both in the first and the se- 
cond stages. Thus I have had 
the opportunity of studying the 
changes, which the larvæ un¬ 
dergo during the metamorphosis 
and to compare these changes 
with those of the larvæ of 
other Muscidæ. 
I a previous paper x ) I have established general characters 
taken from the pharyngeal skeleton and the spiracles in order to 
discriminate the 3 stages of the larvæ of some species belonging 
Fig. 3. Longitudinal section of the 
end of the wall of the tumor on 
the bird represented in Fig. 1. 
9 J. C. Nielsen: Iagttagelser over entoparasitiske Muscidelarver hos 
Arthropoder. København 1909. 
