Category: parasites

The wonders of wasp flight (and parasitism)

July 9, 2024 • 12:45 pm

This video came from FYFD (fyfluiddynamics.com), which has the introductory note:

Personally, I’ve had some bad encounters with wasps, but Dr. Adrian Smith of Ant Lab feels the insects receive short shrift. In this video, he shows many species in the order — most of which are venomless and stingless. In high-speed video, their flight is mesmerizing. Wasps have separate fore- and hindwings, but during flight, they move them like a single wing. Velcro-like hooks on the edges of the wings hold the two together.

From a mechanics perspective, I find this fascinating. Aerodynamically, I’d expect much greater benefits from one large wing over two small ones, but outside of flight, separate wings are more easily tucked away. It’s so neat that wasps have a way to enjoy the benefits of both, enabled by a simple but secure line of hooks. (Video and image credit: Ant Lab/A. Smith)

As I recall, but can’t be arsed to check, insects evolved with four wings at the start, and two-winged insects evolved later, with some converting their wings into balance organs (halteres, as in Drosophila) or wing covers (elytra, like the wing covers of beetles). That’s why wasps had to evolved a velcro-like structure to keep their wings together.

The photography here is marvelous. Try to figure out how some wasps can detect a the larvae of a wood-boring insect inside a tree, and then use their ovipositors to inject an egg into the hapless insect through the wood. They have to be accurate, and do this through a substantial thickness of wood.

h/t: Erik

 

Readers’ wildlife photos

March 18, 2023 • 8:15 am

Tony Eales from Australia has sent us some insects and spiders fatally infected with parasitic fungus. TRIGGER WARNING: ARTHROPOD DEATH!  His captions are indented, and you can enlarge the photos by clicking on them.

With the TV show The Last of Us and its fungi infected zombie antagonists in the zeitgeist, I thought I’d send through some pics of entomopathogenic fungi that I haven’t sent before.

This first one is either icing sugar fungus or a close relative, Beauveria sp. infecting a native wood cockroach (Family Ectobiidae) of some sort. It was hard to tell if the picture was in focus or not with the diffuse fuzzy nature of the fungus

Next might be a fungus in the family Entomophthoraceae. This family generally infect flies and other dipterans but there is a genus that specialises in cicadas, Massospora spp. Perhaps this is related? The host cicada is  or Frog Cicada.

Both the previous fungi I found in the tropical rainforests of North Queensland. The rest of these are from the subtropical areas around Brisbane, southeast Queensland.

Here we have the more typical form and host of Entomorpthoraceae, one of the fly-death fungus species complex. They are easily recognised by the way the light-coloured fungi bursts from between the darker abdominal tergites forming a striped look to the dead fly.

The rest of the fungi are in the family Cordycipitaceae as was the Icing Sugar Fungi up top.

Since I spend a lot of time looking for hidden and well camouflaged spiders, I come across a lot of  Gibellula ssp. This group of fungi really like spiders and I am presuming that the hosts in all of these following five pictures are small spiders of one sort or another (although with some it’s very hard to tell).

The only one that I can ID to species is the last one. This unfortunate is a male Green Jumping Spider, Mopsus mormon, the largest jumping spider in Australia and common garden resident in subtropical areas.
Next is what I suspect is Hirsutella sp. I really can’t tell much about the host but I have seen Hirsutella on planthoppers before and the location under a leaf would be consistent with this group.

And lastly Ophiocordyceps dipterigena, another species that targets flies. I often found it on robber flies perched out on the end of twig in drier forests in SE Queensland.

Readers’ wildlife tales

May 25, 2022 • 8:00 am

Today’s bit of enlightenment comes from Athayde Tonhasca Júnior, and is on a subject that makes some people squeamish. But read on!

‘Thick-headed undertakers in the night of the living dead’

If you watched Alien, you may have jumped out of your seat when the baby monster burst from the astronaut’s chest. But an entomologist may have nodded knowingly: ‘Ah, a human parasitoid!’ Indeed, the screenwriters acknowledged entomological inspirations for coming up with the alien’s life cycle.

Here on Earth, a parasitoid is an insect whose larva develops inside the body of a host (usually another insect), eventually killing it. This type of life history lies between a predator’s and a parasite’s: a predator such as a dragonfly takes several prey and kills them outright, while parasites such as lice, fleas and ticks live off hosts without killing them.

Wasps account for most parasitoid species, but quite a few of them are flies. These include the 800 or so species of thick-headed flies (family Conopidae). A look at one of them explains their common name, although some species look more like wasps or bees than flies. They are also known as bee-grabbers or conopids.

Fig. 1. A conopid fly © Fir0002, Wikipedia.

Thick-headed flies hang around flowers looking for a sip of nectar. But a female may have other ideas: she may be waiting for an opportunity to lay her eggs, which is bad news for a bee or wasp.

It goes like this: an unsuspecting bumble bee worker approaches a flower. A female conopid closes in and grabs the bee in mid-air. Still afloat, she pries open the bumble bee’s abdominal segments with her theca, which is a pad-like, hardened structure at the end of her abdomen. Sometimes attacker and victim fall to the ground, but the outcome is the same; the female fly lays a single egg inside the bumble bee and lets it go.

Fig 2. A female conopid with her menacing theca clearly visible © Hectonichus, Wikipedia.

The drama is over within seconds, and both insects fly away. The fly will stalk another quarry. But the bumble bee is done for.

The egg hatches and the conopid larva develops inside the bumble bee, consuming her innards. But the larva does not penetrate the host’s thorax, thus leaving her flight muscles intact. The bee carries on with her life, feeding and taking nectar back to her nest, although less and less efficiently as the parasitoid grows. Within 10 to 12 days her abdomen is completely taken up by the larva, which has nothing more to eat. The bee dies and falls to the ground (if you find a dead bumble bee with a swollen abdomen, conopid parasitism could be the causa mortis). The larva pupates and overwinters inside the bee’s body, and the adult emerges in the following year.

Fig. 3. A conopid puparium inside the abdomen of a Centris analis bee © Moure-Oliveira et al., 2019. The Science of Nature 106. 10.1007/s00114-019-1634-9.

Some conopids increase the chances of their pupae making it through the winter with a trick that may seem macabre to human eyes: they induce their bumblebee hosts to dig their own graves. In North America, bumblebees parasitized by the conopid Physocephala tibialis bury themselves in the ground just before popping the clogs. This grave-digging behaviour does not make a difference for the bee, but the parasitoid pupa is sheltered from cold and dehydration during winter months, and less exposed to pathogens and its own parasites. Hibernation in the soil also promotes larger and healthier adult flies.

Fig. 4. The grave-digging inducer Physocephala tibialis © Beatriz Moisset, Wikipedia.

But bees don’t take it lying down. When parasitism pressure becomes too high, some species reproduce later in the year to avoid peaks of conopid populations. And some bumblebees – like many other insects – secrete melanin, which encapsulates and suffocates internal parasites. It is estimated that melanisation kills up to 30% of conopid larvae.

Fig. 5. A larva with encapsulated wasp eggs © Nathan T. Mortimer, Illinois State University.

After a parasitized bumblebee has dug its burial pit somewhere in America, a cold, drizzly night falls over the land. All is quiet. Until in an apiary nearby, one of the resident honey bees (Apis mellifera) does something odd: she emerges from the hive and flies towards a streetlight glowing faintly in the distance. A few of her sisters follow suit, although some of them fall to the ground and begin walking around in circles, apparently confused. None of these night wanderers will ever return to the hive; soon they will all be dead. They have been victims of a parasitoid ominously named the zombie fly (Apocephalus borealis).

Fig. 6. A female zombie fly © Core et al., 2012. PLoS One 7(1): e29639.

This fly belongs to one of the largest insect groups, the family Phoridae. They comprise about 4,000 described species, but specialists believe this number represents a fraction of the total. Phorids look like fruit flies with arched backs, and when spooked they run away before taking flight. Such behaviours explain their common names: hump-backed flies or scuttle flies. They are everywhere, and have a variety of feeding habits such as saprophagy (they eat decaying organic matter), predation, and herbivory. One species is a serious pest of cultivated mushrooms.

Two groups of Phorid flies, the genera Pseudacteon and Apocephalus, are found mostly in South America and are charmingly known as ant-decapitating flies. A typical species approaches an ant from behind and uses its powerful, hooked ovipositor to inject an egg in the victim’s head or thorax.

Fig. 7. The hooked ovipositor of Pseudacteon curvatus, a decapitating fly © Sanford Porter, Wikipedia.

The resulting larva moves to the ant’s head, where it feeds on hemolymph (‘blood’) and tissues. Eventually, the larva consumes all the head’s contents, causing the ant to wander around erratically. In two to four weeks, the larva is ready to pupate. It releases enzymes that dissolve the tissues attaching the ant’s head to its body. The head falls off, and the fly pupates inside it before emerging as an adult. These flies are efficient ant killers, and therefore are promising biological control agents against invasive species such as fire ants (Solenopsis spp.).

Fig. 8. A) An ant-decapitating fly (Pseudacteon sp.) preparing to inject an egg into the thorax of a fire ant. B) A decapitated ant with a fly maggot consuming the contents of its head © Porter & Gilbert, 2005. International Symposium on Biological Control of Arthropods.

The zombie fly does not decapitate honey bees, but much of its life history is similar to those of its tropical relatives. It lays its eggs in the abdomen of the bee. The larvae feed on hemolymph and flight muscles, and when they are done, they leave the host to pupate outside. Up to 13 larvae have been observed coming out of a dead honey bee.

Fig. 9. A zombie fly ovipositing into the abdomen of a honey bee worker © Core et al., 2012. PLoS One 7(1): e29639.

Fig. 10. Two fly larvae leaving the host at the junction of the head and thorax © Core et al., 2012. PLoS One 7(1): e29639.

We don’t know why a parasitized honey bee abandons her nest, especially at night, to wander on a suicidal excursion. Her neurological wiring may have been highjacked by the fly, inducing the bee to seek a safer place for the development of the parasitoid’s eggs and larvae. The bee may have been forced out by her healthy sisters; or she left the colony on her own, acting on an altruistic instinct to avoid an epidemic.

Fig. 11. Four zombie fly pupae surrounding the dead honey bee from which they emerged © John Hafernik, University of Florida Entomology and Nematology Department.

The zombie fly is native to North America, where it has long been known to parasitize bumble bees and wasps. Then in 2009, there was an alarming discovery: the fly was also attacking honey bees in parts of the country. And there was more bad news to come. The zombie fly harbours the fungus Nosema ceranae and the Deformed Wing Virus, which are serious threats to honey bees. Researchers don’t know yet whether the zombie fly plays a role in the transmission of those pathogens to bees, but the possibility is worrying.

Conopids and zombie flies are some of the many parasites and parasitoids capable of changing hosts’ behaviour for their own benefit. Some wasps turn ladybirds into paralysed living shields over their eggs, and some fungi make ants climb up plants so they can release spores into the air. Perhaps the most notorious case is the effect of toxoplasmosis cells on rats and mice. Infected rodents become attracted to cat’s urine and are less likely to hide. This altered behaviour is a death wish: they became easy prey for cats, in which toxoplasmosis cells complete their development. Carl Zimmer discussed many other examples in his excellent Parasite Rex; you can read about some of them here.

Parasitism seems gruesome and cruel. Even Darwin was dismayed by it, as he expressed in one of his letters: ‘I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidæ [ a group of parasitic wasps] with the express intention of their feeding within the living bodies of caterpillars.’* But such anthropomorphism is misguided and biased. Parasitoids, predators and parasites are regulators of the natural world: about 10% of all known insect species are parasitoids, although specialists believe this figure is a huge underestimation. They prevent excessive population growth, including of agricultural pests and disease vectors. Parasitism helps shape biodiversity and ecosystems, so it is not intrinsically bad or good. It is a characteristic of life on our planet.

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* This famous quotation inspired a team of ichneumonid specialists to propose in 2019 ‘Darwin wasps’ as a vernacular name for this group of insects, so that they may become better known and appreciated.

Fig. 12. A Darwin wasp © Charles J. Sharp, Wikipedia.

Readers’ wildlife tale

January 31, 2022 • 9:00 am

 

Today we have a special contribution by Athayde Tonhasca Júnior. The photos are not his, but he’s writteen an illustrated mini-essay on a case of parasitism. Athayde’s words are indented, and you can enlarge the photos by clicking on them.  You don’t often see life cycles as complicated as this one!

If you are getting low on wildlife contributions, your readers may enjoy -(or be horrified by, depending on one’s take) an introduction to stylopids.

 

Stylopized, emasculated and zombified: the risks of visiting a flower

‘Bizarre’ and ‘weird’ are overused adjectives for describing many characters and events of the natural world. Life is way too complex and varied to conform to familiar patterns, so the out-of-the ordinary is all around us, even though we not always see it. But when the discussion turns to stylopids, it’s difficult to avoid talking about the bizarre and the weird.

Stylopids (or stylops) are small, seldom seen and poorly known insects with about 700 described species, 10 to 16 of them in Britain. The true figures are likely to be much higher. They are parasites of other insects such as bees, wasps, plant hoppers and leaf hoppers. From a distance, male stylopids can be mistaken for flies, but their ruffled wings give them away and explain the name of this group of insects: the order Strepsiptera, from the Greek strephein (to twist) and pteron (wing). Twisted-wing insects is another common name for them.

Males have branched antennae and their eyes are berry-like structures comprising dozens of image-forming eyelets. This unusual array inspired the development of new cameras of reduced size and sharp images, which are handy for smartphones. Males cannot feed because their mouthparts are not developed. But never mind going hungry; they don’t live for more than a few hours. Their only objective in life is to use their fancy eyes to find a female and mate.

Females look nothing like the males. In fact, they don’t look like your ordinary insect at all because they don’t have wings, antennae, legs, mouthparts or eyes: they are neotenic, i.e., they retain their larval features. An adult female does not need a fully formed body since she never leaves her host: she will develop and die semi-buried in another insect. ‘Semi-buried’ because the tip of her cephalothorax (the head and the thorax fused together) protrudes from the host’s abdomen.

A bee carrying a female stylopid. Scale bars = 1 mm © Soon, V. et al. 2012. Entomologica Fennica 22: 213-218.

Through this exposed area, the female releases a pheromone to attract males. Once suitors finds her, they face an anatomical challenge. Only parts of her head/thorax are exposed, which doesn’t bode well for conventional insect romance. But this setback is nothing compared to the facts that she doesn’t have genitalia, and her eggs float in the haemolymph (‘blood’). So a male has only one course of action: the disturbingly sounding traumatic or hypodermic insemination. He pierces the female’s cuticle with his penis and injects his sperm into her haemolymph. Watch it at this link.

Two male stylopids going after a female tucked in a bee © W. Rutkies at Peinert et al. 2016. Scientific Reports 6: 25052

The deed done, males soon die. The fertilised eggs hatch inside the female, giving birth to thousands of tiny planidia (singular planidium, from the Greek planis, meaning ‘wanderer’). These are a type of larva that don’t look at all like larvae. They have well developed legs, are quite nimble, and they’re phoretic, that is, they use another organism to be transported to a new location. The planidia feed on mum’s innards and eventually crawl out of her body to disperse and start looking for a host of their own.

A stylopid planidium, and planidia emerging from a female stylopid. Scale bars = 0.1 mm © Kathirithamby, J. 2018. Biodiversity of Strepsiptera

A wandering planidium climbs a flower to wait for an unsuspecting visitor. When a bee or wasp lands, the planidium somehow hitchhikes a ride to their nest. We are not sure how it does this: it could hide in the pollen, or possibly be swallowed with the nectar sucked up by the flower visitor, then released when the host regurgitates nectar inside the nest. Chances are it will end up in the wrong nest, so most planidia are done for. But the staggering fecundity of female stylopids compensates bad odds: they can dish out 750,000 planidia, so a few are likely to find a suitable host.

Once inside the right nest, the planidium burrows into a host’s egg or larva and transforms into a traditional legless, grub-like larva. It is followed by other larval stages, pupation, and finally adulthood – by then the host has also become an adult. If it’s a male stylopid, it squeezes out of the host and flies away, usually leaving a big gap behind and killing the host. If it’s a female, it will park itself in the host’s abdomen.

A male stylopid emerging from a wasp © Kathirithamby, J. 2009. Annual Review of Entomology 54: 227–49

 

JAC: I added this video of a male emerging:

The story above is a peep at stylopids’ life histories, as there is considerable variation depending on the species and type of host. And if all this sounds outlandish, there is more to come:

Stylopization (parasitism by stylopids) causes all sorts of physical and behavioural eccentricities in the host, all for the parasite’s advantage. Host infertility is one example. Reproduction involves mating, nest building, nest provision, etc., all of which are risky and energy-consuming, and therefore not beneficial for a parasite. Stylopids solve this problem by disabling the host’s reproductive organs, functionally castrating them. Some stylopized bees have reduced scopae (pollen-carrying structures) and seldom if ever carry pollen: there’s no point, as they don’t have a brood to provide for. Contrary to what happens to most parasitized insects, stylopization often lengthens host development; they live longer so that stylopids have more time to mature. Some stylopized bees are led to stand still on a grass or flower stems with their head downwards. Such a zombie state greatly facilitates stylopids’ mating business.

In Britain, furrow bees (genera Halictus and Lasioglossum), yellow-face bees (genus Hylaeus) and especially mining bees (genus Andrena) are victims of stylopids, but we have little information about their interactions and no idea about consequences of parasitism.

Stylopids are odd and enigmatic, but they are also one of the most complex and intriguing groups of animals. They are evolutionary marvels that have puzzled and awed generations of entomologists and naturalists, and more surprises will be revealed from future research. It seems quite fitting, then, for the august Royal Entomological Society to have adopted a stylopid (Stylops kirbii) as a representative of the organisation:

Royal Entomological Society badge © Wikipedia Creative Commons

Readers’ wildlife photos

May 28, 2021 • 8:00 am

I am running dangerously low on photos, and worry that I will have to cancel this feature or make it more sporadic. If you have good wildlife (or “street”) photos, please send them in pronto. If you’re an American, you have a long weekend coming up to peruse your photos.

All photographers’ words and captions are indented, and you can enlarge the photos by clicking on them.

We have a potpourri today, the first coming from reader Jonathan Storm.

I found this dead grasshopper on an eastern hemlock in the Blue Ridge Mountains of South Carolina. It was killed by an entomopathogenic fungus last summer or fall. These fungi are parasites that infect and eventually kill their insect host. Last summer, a fungal spore landed on this grasshopper and worked its way into the body cavity. The fungus then grew and spread until it killed the grasshopper. Several fruiting bodies of the fungus later grew out of the grasshopper and released their spores into the breeze. Some of these spores will then infect a new insect host and the cycle continues.

A gorgeous Cyclops moth (Antheraea polyphemus) from reader Smith Powell, photographed by Jennifer Lawson:

My granddaughter, Jennifer Lawson, photographed this moth on 02 May 2021 in the family yard in Arlington, Texas. I think this is the prettiest photograph that I have seen of Antheraea polyphemus.

As I’m not a biologist, I had no idea what it was, but I was quickly able to identify it as the Cyclops moth.  Indeed, several websites so identify it and note that it is named for the race of one-eyed Cyclops famously described in the Odyssey. The sites even say that Cyclops means one-eyed.

But, it doesn’t!  Besides, this moth has two eyespots.  Cyclops means “round eye”.  And this photograph shows the eyespots as very round or spherical.

Jennifer’s father, Clint, told me, “ We used to tell our baseball umpires ‘if you had another eye you’d be a cyclops ‘“.

And a pair of Great Tits from reader Pyers:

A Great Tit (Parus major) saying hello from the nest box in my garden:

And have a female Great Tit. the even more cute partner of the one I sent you the other day 🙂

Readers’ wildlife photos and videos

May 14, 2021 • 8:00 am

I am running worryingly low on readers’ photos, so PLEASE send in your good ones. I don’t want to have to cancel this feature or put it up sporadically. Thanks!

We have a potpourri of photos and movies today. Readers’ captions are indented, and you can enlarge the photos by clicking on them.

The first two photos are by Andrea Kenner.

Here’s a photo of my first sighting of a Brood X cicada. The baby is sitting on the sidewalk in Hyattsville, Maryland. I’m not sure which species he is (there are three). Here’s a link to the Wikipedia page.

I took this photo in my front yard in Prince George’s County, MD, and posted it on Facebook. The tree is an Eastern Redbud (Cercis canadensis). An entomologist in my neighborhood identified the bee as a Hairy Footed Flower Bee (Anthophora villosula), a recently introduced species in the Mid-Atlantic region.

From Linda Mercer:

It is hard to see the tiny fawn hiding behind my air conditioner.

A duck video from Brian Tarr:

I’ve been an avid lurker on your excellent website for several years, and have finally plucked up the courage to share a bit of wildlife with you. This is a sord of mallards which I filmed this last winter in Łuków, Poland, by the Southern Krzna River in the central park. I thought it a bit unusual to see so many, because I figured they would have flown south by then. As you can see, they are quite accustomed to humans, as people often come with their children to toss them bread (not the ideal diet, as I learned from you).

Please feel free to share this with your readers, if you so choose. I would love to get some feedback about migratory patterns. (Possible aberration due to climate change?)

 

And a parasitized grasshopper from Jonathan Storm:

I found this dead grasshopper on an eastern hemlock in the Blue Ridge Mountains of South Carolina. It was killed by an entomopathogenic fungus last summer or fall. These fungi are parasites that infect and eventually kill their insect host. Last summer, a fungal spore landed on this grasshopper and worked its way into the body cavity. The fungus then grew and spread until it killed the grasshopper. Several fruiting bodies of the fungus later grew out of the grasshopper and released their spores into the breeze. Some of these spores will then infect a new insect host and the cycle continues.

And a video from Jonathan:

This female Ruby-throated Hummingbird [Archilochus colubris] was collecting spider silk from a window on my house in South Carolina. The sticky and stretchy nature of the silk help hold the nest together and anchor it on top of a tree branch. Ruby-throated Hummingbirds often construct their nest from dandelion seeds, moss, and lichens and place it high up in a hardwood tree.

Readers’ wildlife photos

January 20, 2021 • 8:30 am

Tony Eales from Queensland weighs in with photos documenting a nice story of parasitism and mimicry, with the mimicry being an orchid that deceives a male wasp into trying to copulate with it. (The gain is pollination for the flower; the wasp gets nothing but frustration.)

Tony’s descriptions are indented; click on the photos to enlarge them.

I came across something quite special on the weekend. It’s a terrestrial orchid Arthrochilus prolixus, AKA Wispy Elbow Orchid.

This orchid by sight and smell imitates a wingless female Thynnid wasp. Female Thynnids often sit at the top of a blade of grass waiting for a male to find them. It is this behaviour the orchid takes advantage of.

JAC: Note how the orchid above imitates a waiting female.  The male mates with the orchid, getting pollen on its back, and then, because wasps aren’t that smart, eventually tries to mate with a different orchid, whereupon the pollen from the first orchid detaches and pollinates the second one. (Note the stamens in the orchid at lower right above.) This is known as pollination by “pseudocopulation.”

Thynnid males pick up females and carry them around while mating for many hours.

Thynnids are parasitoids of scarab beetle larvae. Scarabs live under ground or within litter for a year or more, feeding and growing. As larvae they are often known as Curl Grubs (and I realise I don’t have any photos of curl grubs which is strange, only adults). [JAC: see a photo here.]

The females deposit a single egg on any scarab larvae they find which grows and eats the larvae until emerging as an adult wasp and digging out.

Here’s a photo of a male I observed busily pulling back leaves off the ground as a newly emerged female was making her way out.

There are around 2000 species of Thynnid in Australia of which only about a quarter have been described and named. As far as I can tell no-one yet knows the species that pollinates the orchid that I found.

Here’s a good article on Australian Thynnids for the layperson.

And here is a paper describing how a different species of elbow orchid tricks the wasps into getting a wad of pollen attached to the right spot on their back with great pictures.