#mymaridae

Mymaridae is a diverse family of wasps that contains more than 1,400 known species, and these wasps are often described as fairy wasps (or "fairy flies") because they are so incredibly tiny. In fact, these are some of the smallest multicellular animals ever described, with most fairy wasps measuring less than 1mm long.

Above: Lymaenon aureus, a species of fairy wasp, depicted on top of a lime

One species of fairy wasp, Dicopomorpha echmepterygis, is the smallest insect known to science. The adult males of that species can measure as little as 0.139mm (139 microns) long, which is roughly the size of a single human egg.

Above: Anagrus fairy wasp

As this article explains:

Fairyflies are not actual flies at all, but chalcid wasps; they get their name because of their fairy-like wings, and for being tiny and "invisible" like the mythical fairies. Fairyflies have the smallest known adult form of any insect: wingless and blind males of the species Dicopomorpha echmepterygis have a body length of just 0.139 mm, about the average width of a human hair. The fairyfly family Mymaridae consists of many species, including Tinkerbella nana and Kikiki huna, the smallest known flying insect species with a body length of 0.16 mm.

Above: the photo at the top shows a fairy wasp of the genus Anagrus, while the photo on the bottom shows another species from genus Polynema

Most fairy wasps have fully-functional wings that are lined with long, feathery bristles:

Fairyfly wings are not only small, but their structure is comb-like and made of several bristles instead of a planar sheet. Their very small size means that the air around them is more viscous than it would be for larger insects. At such small scale, the ratio of inertia to viscosity, the Reynolds number, is so low that any movement provided to an air packet quickly dampens out. It also means that a single wing bristle drags along with it a boundary layer of a comparable size. Thus, if the bristles are sufficiently close, the comb-like wing can act as a paddle to generate the requisite aerodynamic forces, while reducing the overall mass of the wing.

Above: a fairy wasp depicted beneath a push-pin

All of the wasps in this family are parasitoids, and they lay their own eggs within the eggs of other insects. Their hosts include aphids, scale insects, booklice, thrips, water beetles, and other tiny arthropods; the female fairy wasp inserts her ovipositor into the host's egg and then deposits her own offspring within.

Above: this composite image shows male and female fairy wasps of the genus Polynema standing on a pinhead

This seems like a good time to point out that fairy wasps do not parasitize mammalian ova, nor do they parasitize the eggs of any other vertebrates, and they are completely harmless to humans. In fact, they're actually beneficial, since they often parasitize agricultural pests.

Above: a fairy wasp trapped in a tiny guttation drop produced by a fungus

I posted some information about fairy bees a few weeks ago, so I figured that I should share these little fairy wasps, too.

Above: a Mymar fairy wasp with an aphid standing nearby

Sources & More Info:

Current Biology: Fairyflies

Annual Review of Entomology: Small is Beautiful: Features of the Smallest Insects and Limits to Miniaturization (PDF)

Journal of Hymenoptera Research: A New Genus and Species of Fairyfly, Tinkerbella nana, with Comments on its Sister Genus Kikiki, and Discussion on Small Size Limits in Arthropods (PDF)

The degree to which they live their life in water varies, but almost all of them parasitise aquatic insect larvae – with the exception of the spider wasp Anoplius depressipes, which parasitises fishing spiders instead – and their offspring have to swim back out once they emerge as adults. A lot of them have longer claws than other wasps to help with gripping vegetation underwater and hairs that can trap air and make them somewhat hydrophobic. And they're all largely unrelated, they're thought to have evolved being aquatic at least 50 times separately!

Anoplius depressipes

One neat one I want to point out is Caraphractus cinctus. It's a fairyfly (Mymaridae), and if you've heard of them, you've probably heard they're small enough that they essentially swim through the air with their feather-like wings. C. cinctus takes that a little further by. Well. Swimming. They emerge as adults from the parasitised eggs of diving beetles (Dytiscidae) and the females immediately begin searching for new eggs, moving through the water using their wings and taking in oxygen from the water. They are seemingly able to survive for up to 15 days below the surface, and if beetle eggs are available then most females never do leave the water. Mating usually occurs underwater, although not within the beetle eggs as the Bennett paper says. I find it really cool that they can break through the surface tension by diving in head first, although they tend to just use vegetation to help them down.

From Jackson (1958)

Another really cool one is Hydrophylita emporos, which sometimes locates its host's eggs by catching a ride on the adult female damselfly's (Psolodesmus mandarinus mandarinus) abdomen and running down to lay their own once she starts ovipositing. Some, like C. cinctus, stay below the water their whole lives.

Hydrophylita emporos on the back of Psolodesmus mandarinus mandarinus, CC BY 2.5

Also, one of them is named after Godzilla (Microgaster godzilla). I think that's very important

Bennett, A.M.R. (2008) 'Global diversity of hymenopterans (Hymenoptera; Insecta) in freshwater', Hydrobiologia, 595, pp. 529–534

Jackson, D.J. (1958) 'Observations on the biology of Caraphractus cinctus Walker (Hymenoptera: Mymaridae), a parasitoid of the eggs of Dytiscidae (Coleoptera) – I. Methods of rearing and numbers bred on different host eggs', Transactions of the Royal Entomological Society of London, 110(17), pp. 533–554

Jackson, D.J. (1961) 'Observations on the biology of Caraphractus cinctus Walker (Hymenoptera: Mymaridae), a parasitoid of the eggs of Dytiscidae (Coleoptera) – II. Immature stages and seasonal history with a review of Mymarid larvae', Parasitology, 51(3–4), pp. 269–294 (not really referenced here but this isn't an essay it doesn't need to be one to one right)

Jackson, D.J. (1966) 'Observations on the biology of Caraphractus cinctus Walker (Hymenoptera: Mymaridae), a parasitoid of the eggs of Dytiscidae (Coleoptera) – III. The adult life and sex ratio', Transactions of the Royal Entomological Society of London, 118(2), pp. 23–49 (these three are unfortunately not open access but if you can use sci-hub then 👀)

Shih Y.T. et al. (2013) 'Hydrophylita (Lutzimicron) emporos Shih & Polaszek (Hymenoptera: Trichogrammatidae) from Taiwan, parasitising eggs, and phoretic on adults, of the damselfly Psolodesmus mandarinus mandarinus (Zygoptera: Calopterygidae)', PLoS One, 8(7), e69331

If you want to see the world's smallest insect, you'll need to bust out your microscope! The parasitoid wasp Dicopomorpha echmepterygis has the honor of being the smallest insect by body legnth, with males averaging just 186 μm (0.007 in) and females slightly larger, at about 550 μm (0.02 in). That's smaller than some bacteria!

what if you had a fairy godmother but she was <1 mm long

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Fairyflies are among the smallest insects on Earth. Despite their diminutive size, these remarkable animals play a crucial and specialized role in their environments by parasitizing the eggs of other insects. Once she finds a suitable egg, she deposits her own within. The female fairyfly relies on the eggs of other insects as both a shelter and a food source for her offspring. By utilizing the resources provided by other species, she ensures the survival of her own progeny while simultaneously managing the population of potential pests. Regulating these host populations can have profound effects, as parasites are integral to shaping and balancing ecosystems. This relationship demonstrates the interconnectedness of all living beings and the importance of mutual support.

This card imparts the wisdom of recognizing and valuing the talents of those around you. It emphasizes the importance of collaboration with individuals who bring diverse viewpoints, experiences, and expertise to the table, enabling you to achieve far beyond what you could imagine. Whether you are embarking on a creative project, starting a business venture, or tackling a personal challenge, this card advises you to enlist the support of others and to leverage their expertise for mutual benefit. At its core, the Three of Galls is a card of achievement through teamwork. It suggests that by pooling your resources, talents, and efforts with those of others, you can create something of enduring value and significance.

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