Ecological impact of ladybug harvesting

We're interested in finding out more information on the commercial
harvesting of Hippodamia convergens (the Ladybird Beetle.) We supply
beneficial insects to farmers and gardeners through our mail-order catalog,
and we've been concerned about recent shortages in supply. We were told by
our supplier that the commercial harvesters went up into the mountains
(presumably the CA Sierras) this spring and found that the beetles had
migrated "prematurely." The harvesters came back with much fewer insects
than usual, hence the short supply. For several weeks we've been faced with
a total moratorium on ladybug sales until the first or second week of June.
Our customers are very frustrated by this lack of supply, and in our
efforts to explain the situation, we find that we're sorely lacking in
information on this subject. What we're most concerned about is the
sustainability of these practices. Are commercially-available ladybugs
raised in captivity or are the majority of ladybugs sold in the US captured
in the wild. And if so, what is the impact of this practice on the ecology
of the ladybug and on the environment. We'd greatly appreciate any and all
input on this matter. Thank you.

Cheryl Gish

Snow Pond Farm Supply
RR 2 Box 1009
Belgrade, ME 04917
Ph:    (207) 877-0870
Fax:   (207) 872-0929