Cockerell's "private collection"?

[Doug Yanega]

It's become necessary for me to examine the type of the bee Psithyrus
bicolor Franklin, but the only data I can find on depository is Franklin's
comment that it is deposited in "Prof. T.D.A. Cockerell's private
collection." No one here seems to be entirely certain where that material
resides presently, or if it is even in only one location. The leading
candidate is Boulder, Colorado, but rather than continuing to grope
blindly, I figured maybe someone here could give a definitive answer. I
suspect private response is better.
Thanks in advance,

Doug Yanega       Illinois Natural History Survey, 607 E. Peabody Dr.
Champaign, IL 61820 USA      phone (217) 244-6817, fax (217) 333-4949
 affiliate, Univ. of Illinois Urbana-Champaign, Dept. of Entomology
          http://www.inhs.uiuc.edu:80/~dyanega/my_home.html
  "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82