Bug Mums- The Invertebrates that Invest in Motherhood

When we consider maternal care in the animal kingdom, we tend to hold up mammals and birds as shining examples, whilst regarding reptiles, amphibians and invertebrates as absolving responsibility, leaving their eggs to get on with life. Ants, bees, wasps and termites are obvious exceptions, with the young protected and provided for by their mothers or worker siblings in the nest.  You may not know that many invertebrates are excellent mothers too. On a day of appreciation for the human mother’s of the world, let’s take a look at some unlikely maternal heroes. Their identities might surprise you.

Scorpions- The Piggybacker

These pincer-clawed arachnids certainly have a sting in the tail, but they also have a gentler side. To start with, the baby scorpions are nourished inside the mother via a kind of placenta and enter the world as live young. Despite this auspicious start, the babies (known as ‘scorplings’) are soft and defenceless. The mother carries her scorplings huddled on her back under the protection of her sting until they develop their own defences. A clear case of don’t mess with Mum!
Considering she may carry up to 100 scorplings for 20 days this is quite some dedication. However, it may be a stretch to call it motherly love, as a starving scorpion may snack on her scorplings as a last resort.


Mother scorpion carrying her scorplings. (c) JawnTEM. Wikimedia Commons.

Leeches- The hugger

Leeches may be the last animal you think of as caring. We use ‘leech’ as a term for someone who takes without giving, but Freshwater Jawless Leeches in the genus Helobdella are paragons of motherhood. The mother leech lays egg cocoons, which she sticks to her belly, carrying them around wherever she goes. When the babies hatch they also stick with her, and mum provides meals by catching and passing them tiny worms with her proboscis-like mouth. After a few weeks of this cuddling and catering, the little leeches can grow to six times their hatching size, making them better able to fend off predators when they leave their mother’s protection.
If you’re still not convinced that leeches can be lovely, note that Helobdella aren’t blood suckers at all-they prefer to guzzle smaller invertebrates.

Earwigs – the broody hen

Earwigs may seem like unassuming insects, often even reviled, but they are amongst nature’s most devoted mothers. When earwigs are expecting, they find a secure spot underground and excavate a nest chamber (never in a human brain as the playground myth goes!). Here she lays a clutch of eggs and dotes over them like a broody hen, protecting them from predators and parasites and ‘licking’ them with her mouthparts to prevent fungal infections. When the nymphs hatch, the mother continues to protect and feed them until they leave the nest. The pincers on her rear come in handy as protective weapon against predatory beetles and centipedes.

Mother earwig in her brood chamber with her eggs and hatchling nymphs (c) Nabokov. Wikimedia Commons.

Centipedes- the protectors

Many centipedes themselves are also excellent parents. Female Stone Centipedes and Giant Centipedes coil around their eggs, clutching them with their clawed legs. Like earwigs, the mother centipede anoints the eggs to protect them from pathogens, and even delicately turns them with her sharp, venomous fangs. Stone centipedes do not hunt during this time, so fast for 50 days or more. When the babies hatch, the mother centipede hugs them with a many-legged embrace, guarding them through a number of moults. If a predator attacks, some centipede mothers  will curl their rear body around their young, and lash out with their venomous fangs like a cobra. An effective defence considering the bite of some giant centipedes is even agonising to humans!

A mother centipede tending her eggs (c) Cody Hough CC-By-2.0.

Mothercare spider- the provider

Spiders on the whole are excellent mothers, with varying parenting styles, from guarding their egg sac to carrying their spiderlings on their back and even sacrificing themselves as baby food! One species is so devoted it’s named for it. The Mothercare Spider Phylloneta sisyphia is a tiny (5mm long), harmless, rotund spider in the same family as Black widows, spinning webs in shrubs across Europe.
When the time comes to live up to her name, the female mothercare spider builds a silk ‘nursery tent’ in her web, camouflaged with plant material as a safe space to suspend her silken egg sac. This tent acts as a room and hideout for her many spiderlings when they hatch. All these little mouths get hungry, and when they do, they appear to throw a tantrum, seeking out their mother and tagging her legs. Responding to this unsubtle signal, she regurgitates food for them like a mother bird, a nutritious soup or pre-digested insects and her own intestinal cells. Tasty! When the spiderlings grow a little, she shares her insect catches. After all this effort, the mother never lives to see her offspring grow up. After passing away in the web, she becomes their last meal before they depart. This eight-legged mother is devoted to the end.

File:Theridion.sisyphium.female.with.egg.sac.jpg
A Mothercare spider guards her blue-green silk egg sac within the nursery tent she has spun. (c) James K.Lindsey. Wikimedia Commons.

Bromeliad crab- the home maker

Though most mother crabs carry their eggs for a while and cast their babies away into the water, the Bromeliad crab Metapaulias depressus goes to extraordinary lengths to provide for her family. This tiny crustacean inhabits pools in the leaf-bases of rainforest Bromeliads- South American plants that grow on tree branches. This might seem like the perfect quaint little refuge to bring up babies, but most of these leaf pools are so small they quickly dry out, and even those are often full of leaf mould from the canopy above, creating stagnant, acidic conditions that delicate crab larvae can’t cope with.

The expectant little mother crab must make some big home improvements with her own two claws. After choosing a large nursery pool that is likely to stay full and fighting off competing females, she diligently removes the sodden leaf litter and other debris. With one exception. The crab leaves and adds empty snail shells, since the lime they contain helps neutralise the acidic water. Once cleared out, the pools oxygen content increases and she can finally settle down to breed.  She lays around 50 eggs and holds them cupped in the flap-like abdomen or ‘apron’ under her belly until they hatch.

On hatching, she releases the larvae into the pool, but she doesn’t simply leave them to it. The larvae are strictly aquatic, but have a limited food supply in the pool. The mother ferries back and forth to feed her offspring, foraging around the bromeliad for small invertebrates, which she breaks up into baby food back at the nursery pool. As if this wasn’t enough, she also has to fend off ferocious neighbours, as the pools are often also occupied by predatory damselfly larvae, which can snaffle up five nymphs a day! Like the earwig, her pincers are essential tools for motherhood.

Understandably, the young crabs are reluctant to leave the luxury of their maternal home, and stay around for about 8 weeks as Mum rears further broods of offspring forming a little crab community. This makes them one of few non-insect arthropods that live in family units.

Burying beetle- the co-parenter

Of all the insects, Burying beetles Nicrophorus sp. arguably put the most effort into parenting, and their methods are not for the faint-hearted. It all starts when something fluffy dies- preferably a small mammal or bird. A burying beetle sniffs out the fresh body, and hopefully meets a mate at the carcass, then the two work together to laboriously move and bury an animal several times their size. Once suitably far underground, the pair work together to excavate a brood chamber in the soil, then form the carcass into a ball, stripping the hair or feathers to line the outside, and embalming it with chemical secretions to slow its decay. Within this ball, they make a hollow for a nest, where the female lays her eggs and cares for them.
When the larvae hatch, both parents care for the grubs throughout the larval stage. Like chicks in a nest, the grubs beg for food by rearing their heads, and the parents regurgitate meat from the carcass for them. The parent beetle’s work only stops when the grubs move off to pupate.
Burying beetles are a rare example of biparental care amongst insects- where both the mother and father take care of the offspring. Life clearly isn’t easy for either parent and you could say after all this that she at least deserves a card and some chocolates!

Show your love to your maternal figures this mother’s day. They may not have fought off ravenous predators or shaped a carcass into a home but I’m sure they’re amazing too.

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RoryD

RoryD

Conservation Ecology graduate, with a particular love for the small things. working in conservation and nature outreach, injecting enthusiasm for entomology wherever I can.

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