590 The American Naturalist. [July, 
less studied than the Tachinidae. Professor Riley has proposed 
the feasibility of introducing the European Tachinid parasite of 
the asparagus beetle, but my opinion is that such an attempt 
would fail, though it would certainly be very interesting. The 
difficulty in the way of the insect host may be the cause of such 
non-importation, but it hardly seems so, for many species are 
parasitic upon numerous forms, and American parasites allied to 
the European ones have, in not a few instances, adapted them- 
selves to European insects that have been introduced into, or at 
least occur in, this country. 
In the parasitic family of bot-flies it is probable that all 
the species common to the two countries (eight) have been intro- 
duced with the domestic animals, with the exception of the cir- 
cumpolar reindeer bot-fly. They all occur from the Atlantic 
to the Pacific, — ^that is, those of the United States, — and not a 
single species of their respective genera (leaving out the doubtful 
case of Hypoderma bonassi) is indigeneous. In the genera 
Cuterebra and Cephenomyia not a single species is known to oc- 
cur outside of North America. Among the mosquitoes three or 
four species, from among about forty, are recorded as common to 
the two continents. 
New Haven, Conn. 
EXPLANATION OF PLATE. 
Fig. I. Hcematobia serrata R. Desv., female. 
Fig. 2. Head of male. 
Fig. 3. Head of female. 
Fig. 4. Hind foot of male. 
