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Tuesday, February 21, 2017

Unexpected Liaisons, Mites and Bees

Mason bee with phoretic mites
Wikicommons © Orangeaurochs
We think of mites as annoying tiny parasites that cling to us and make us itch. If we see an insect covered with mites we feel sorry for it, assuming that the poor thing must be itching terribly and being weakened by the blood sucking pest. This is true in most cases, but curiously there are some exceptions. Believe it or not, some bees, wasps and beetles are perfectly happy with such companions. They bus around the little fellows from plants to nests. This earn the passengers the name of phoretic mites.

Carpenter bee (Xylocopa) with phoretic mites
Wikicommons © Gideon Pisanty
Mites and ticks are not insects. They are related to spiders, and most of them have eight legs, just like spiders. Mites are tiny; most of them are smaller than the tip of your ball point pen, so it is not surprising that we know very little about them. We would be quite surprised at the immense variety of mites and the large number of species. Many feed at the expense of animals, like the ones mentioned at the start of this piece, but many more feed on plants, fungi or bacteria.

Acarinarium of carpenter bee (Xylocopa)
Wikicommons © T. B. Fletcher (1914)

Getting back to the mites covering a bee. Little do you know that these particular kind of mites are the bee's friends to the point that the bee provides transport for them. Some bees have a small compartment or pouch on their bodies where mites can ride comfortably to the bee's nest. This organ is called an acarinarium, from the Greek word acarus (plural acari), which means mite.

It turns out that the mites feed on parasites that are prone to invade the bee's nest where she is raising a family. Thus the mite provides a valuable service to the bee which is greatly appreciated and compensated.

Some wasps have a similar mutualistic arrangement with mites and carry them to their nests. Carrion beetles transport mites to fresh carcasses. The mites feed on fly maggots, the beetle's competitors.

Potter wasp with acarinarium

Carrion beetle with phoretic mites
Flickr, Wikimedia. © Bohne, G

2 comments:

  1. Fascinating! Is there any way to tell phoretic mites from other, less benign, mites without examination under a microscope? Cynthia

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  2. We know so little about mites! Yes, probably some can only be identified by using a microscope and having a good knowledge of their life cycle and habits. But in some instances, they can be identified from photos, once again because of their habits. If they ride on a bee, wasp or beetle known to frequently have phoretic mites, that makes it easier. Look at these for instance: http://bugguide.net/node/view/864859 and these: http://bugguide.net/node/view/87680. In other cases, one can tell that they are parasitic even if we don't know the species, for instance, many on this page: http://bugguide.net/node/view/1232686. This poor fleahopper is being devoured by the two big monsters, don't you think? I hope this helps.

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