Dear colleagues--

We regret to tell you that we've discovered mites in Bloomington Stock Center fly cultures and that, unfortunately, we've sent contaminated samples to a few Stock Center users.  Since you've received samples from us within the last three months, we're writing to warn you that the samples may have been contaminated.

The mites we found are common food mites (Tyrophagus putrescentiae).  This is not a species that produces hypopus larvae that cling to adult flies and it is not a predatory species.  The mites will, however, overwhelm cultures and outcompete flies for food if infestations are allowed to persist.

Full grown mites are about the length of a fly egg and will typically be found in and around fly pupal cases.  They eat the molds and fungi that grow in fly cultures.  They like to lay their eggs next to pupal cases.  Mite eggs are much smaller than fly eggs, but they have the same smooth, iridescent surface texture and are identical in color.  Usually, eggs will be seen before mites when scanning the walls of a culture vial.  Mite infestations will typically not be recognized until fly cultures are 3-4 weeks old.

Contaminated cultures may be cleaned up easily by rapid transfer of adult flies to fresh food.  We transfer adults to fresh food for four days in succession and discard the intermediate vials.  After rapid transfer, cleaned up vials should be grown for about a month to assure all mites were eliminated.  We have never found it necessary to use miticides such as Tedion.

We are taking steps to eliminate mites from our cultures, but it will be a long time before we are certain we have the problem under control.  You should continue to quarantine all stocks you receive from us and check them carefully.

We hope to get this mite outbreak under control quickly.

Thanks for your patience,
Kevin Cook
Kathy Matthews
Thom Kaufman
Luke Jacobus