306 
conditions prevailing, say twenty or twenty-five years ago, and 
much of this improvement is due to the excellent work done 
by the numerous species of coccinellid beetles introduced by 
Koebele from the Orient and Australia. But with regard to 
most of the species, and particularly those infesting crop plants, 
the present situation is far from being satisfactory, and a remedy 
should, be sought in the way I have indicated. Mr. Osborn’s 
work in Mexico furnishes an example of what can be done. 
In carrying out an idea of this sort, a primary concern is to 
learn the center of distribution of the noxious species, and to 
that end all the data bearing on this point should be collected 
and carefully considered. Unfortunately, in some cases, the 
available data is valueless for the purpose mentioned. In that 
contingency, the only recourse is to investigate one zoological 
region after another until a fruitful one is found. In other 
cases, however, the way is clearly marked. 
The point is here made that conversely to the proposition 
above stated, the presence of several or numerous parasites of 
a noxious species in any definite region is prima facie evidence 
on the origin or center of distribution of the species. Such evi- 
dence is now available for three of our species, and Mr. Tim- 
berlake has pointed out the weight of evidence with regard to 
two others. 
Another important consideration in an undertaking of this 
kind is ability to recognize any particular species in hand. The 
main purpose of my study was to familiarize myself with the 
different species, so that the material sent in could be handled 
with safety and utilized to the greatest advantage. After gain- 
ing a thorough knowledge of the species, it was easy to formu- 
late the keys here given to the subfamily, genera, and species 
under consideration, which may be useful to others working on 
this group of insects. Thanks to the careful and painstaking 
work of Ferris, Morrison, and others, who have pointed out the 
greater dependability of morphological characters, the distine- 
tion of mealy-bug species now rests upon much surer ground 
than formerly. With regard to the keys just mentioned, I will 
say that I have tried, in the case of species, to combine morpho- 
logical characters in a table with the more obvious distinguish- 
ing marks or traits. I have also sought to indicate my views as 
