their parasites were generally not im- 
ported with them. Nature, left to her 
self, preserved a balance between the 
different forms of life, that could not be 
upset with impunity. The case of the 
European cabbage-butterfly (Pieris rapae) 
was a case in point, in Europe it was 
kept greatly in check by a minute para- 
sitic four winged fly, but this enemy be- 
ing absent in America, until recently im- 
ported by the government, the cabbage- 
butterfly had increased enormously and 
become very harmful. Another similar 
instance was that of the Cottony-cushion 
scale (Icerya purchasi) in California. 
Quite recently, however, the parasite of 
this inssct hac been sent to California by 
a government agent who had been dis- 
patched to Australia, its native home, 
for the purpose of procuring it, and it 
was hoped that it would increase and do 
much good in checking the increase of 
that terrible pest the Icerya. The man- 
ner in which the large Ichnehmon (Tha- 
iessa) deposited its eggs was described, 
and" also the parasitism of Ichneumons 
and Tachina-flies upon caterpillars, and 
the way in which lady -birds and spiders 
were destroyed by parasites. Various 
other matters wers also referred to; the 
parasites of Sawflies, egg-parasites, and 
the destruction of thistles by the thistle- 
bud fly. 
# NOTES. 
We sent the wiijgs of three ducks, shot 
in the Costilla county part of the San 
Luis valley, to Dr. C. H. Merriam. He 
says they are the Red Duck (Erismatura 
rubida,) the Buffle-head (Charitonetta al- 
beola,) and the Gadwall (Anas strepera.) 
The Gadwall is also found in western 
Custer county. 
Dr. Merriam identifies the Mountain 
rat, which is so troublesome in western 
Custer county from about 8,400 to 10,000 
feet altitude, as Neotoma cinerk. He 
has a number of specimens from Boul- 
der county. 
Menopon pallidum is the name of a 
chicken louse, which is sometimes found 
upon chickens in western Custer county. 
There is also a chicken flea — we- have 
seen these sitting in rows, twenty or 
thirty together, on the cracks in a fowl- 
house which was Very rarely cleaned out 
Although there are many species of 
spiders in Custer county, we have only 
been able to get one kind named. This 
is called Azalena nssvia, and was identi- 
fied by the Rev. O. P. Cambridge. Com- 
paritively little is known at present a- 
bout spiders, and doubtless many of our 
sjascies are undescribed. 
In 1887 we found soSef minute shells in 
Delta county, on the south side of the 
Grand Mesa, which differed somewhat 
from anything we had seen, and w T e were 
therefore proposing to call them Pisidium 
mesae. However, after comparing them 
with numerous examples of P. pusillum, 
we are persuaded that they represent 
only a form of that polymorphic species. 
A kind of liverwort, called Marchantia 
polymorpha, is ercceedingly abundant 
on the banks of streams on the east 
slope of the Sangre de Cristo range, in 
in Custer county. Fifteen species of 
liverworts have been found in Colorado. 
T. D. A. C. 
