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

© Stephen Luk

Carrion beetle with phoretic mites

Flickr, Wikimedia. © Bohne, G

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Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2017

The Yucca Moth and the Yucca

Yucca (Yucca glauca), the state flower of New Mexico, illustrates an intimate relationship between a specialized pollinator and its equally specialized flower. The plant and the insect co-evolved; that is, they developed in intimate connection with each other. This is called an obligate mutualism in which if one were to disappear, the other would follow the same path. Originally it was a relationship of exploitation, with the moth larvae feeding on the seeds of the yucca. But, eventually the plant devised methods to take advantage of the situation and as a consequence, the moth also evolved to ensure food for its babies and preservation of its food plant.

Yucca flowers open for a few days, attracting a variety of insects during day hours; but they produce more nectar and send their strong and sweet aroma at night. Flowers with these characteristics are usually pollinated by moths or other nocturnal pollinators.

The yucca adds a special embellishment to this arrangement; of all the insects that visit its flowers, the only ones that can accomplish pollination are the yucca moths (Tegeticula yuccasella and Parategeticula depending on the species of plant).

Yucca moths are small, white, not very noticeable. They spend a good part of their adult life inside the flowers of the yucca, meeting members of the opposite sex and mating. Once mating has taken place, the female, very purposely visits the male parts of the flowers (anthers) to collect pollen which she stores under her chin.

Later, she flies to another flower, inspects it carefully, and if no other female has deposited her eggs, she proceeds to do just that. She refrains from laying more than a small number of eggs. The larvae will feed on the seeds of the plant. She seems to know that if she gets carried away and lays too many eggs, the flower will abort rather than produce a seedless fruit. It would be a no win situation, both for the plant and the moth.

Then, just as purposely as before, she goes to the right place, at the top of the ovary (called stigma), and deposits some of her precious cargo of pollen from under her chin, ensuring, this way, that the seeds will grow and feed her babies. She repeats this operation in other flowers.

The larvae feed on some of the seeds and there are enough left for the plant to reproduce. When fully grown, the larvae drop to the ground, where it goes through the transformation called pupation and finally it emerges as an adult several months later to repeat the cycle.

Without this insignificant little moth, the landscapes of the west would look dramatically different in the absence of yucca.

© Cillas. Wikicommons

Read more:

Tree of Life

Discover the Desert

Moths as Pollinators
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Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012