Hawaiian Happy-face Spider Facts

Hawaiian Happy-face Spider Profile

The human mind is strongly programmed to see faces. We see them in clouds, we see them in letterboxes and if we are not ashamed to catch a glance, we see them on the badunkadunk of a tiny green spider from Hawaii. 

Hawaiian Happy-face Spider Facts Overview

The happy-face pattern on this spider isn’t usually in the shape of a face at all, it actually comes in a variety of patterns and colours that differ between individuals and change as the animal grows.

Researchers are curious about this as a clue as to how polymorphism can work in animals like this and are trying to figure out both how and why it happens. 

Meanwhile, the spiders themselves are enjoying their tiny lives dancing underneath leaves. 

Interesting Hawaiian Happy-face Spider Facts

1. They’re tangle-web spiders

Hawaiian Happy-face Spiders are members of the tangle-web family, which is a common group of true spiders, probably best championed by the black widow. 

There are more than 3,000 other species in this family too, though, and they’re known for having a woolly mess of a web and commonly being found inside people’s houses. They also have a comb of bristles on their legs, lending them the other name, comb-footed spiders. 

There are over 120 accepted genera in this family, Theridion being but one, and this one is characterised by the very long legs of many of its members. The happy-face is no exception, and while it has a 5mm body, its legs may be three times this length each. 

2. They’re good mothers

Mothers of this species appear to put an exceptional degree of work into their parenting, at least by spider standards. 

She’s notably aggressive to anything that threatens her eggs, which is common enough, but she takes it several steps further and stays with the young after they’ve hatched, even feeding them as they start to learn the ropes. 

This process isn’t a bonus, though, it’s necessary – the spiderlings are about as useless as freshly hatched humans and can’t even feed themselves for the first month or so.

They’ll be looked after for up to 100 days if they make it that far. An unguarded egg from this species is finished off by predators within a single week. ¹

3. They dance

Before they get to the egg-laying stage, females engage in courtship rituals with males, and this involves the male playing the female’s web like a fiddle, plucking at the strings in a performance designed to convey reproductive fitness. 

 These spiders are not like the wolfies or the jumping spiders with their excellent eyesight, in fact, they can barely see at all.

And this explains why they need to rely on vibrations and olfactory senses when mating but throws up a puzzling question as to why they’re so colourful. ²

4. They make a lot of faces

The name of this species comes from the occasional spider whose abdominal pattern manifests in the shape of a smiley face. Their real faces look no less cold and intimidating than your standard widow spider, but their arses can look like a right laugh. 

But not always. This pattern is remarkably variable and that’s something of great interest to researchers, who are more familiar with animals of the same species looking a lot more alike. 

So, this polymorphism, as it’s called, is quite a fun thing to study, and in this species, there are several discrete colour morphs, each showing up with roughly the same frequency in every population. 

How this happens is still a matter of research, but there are some clues emerging. 

5. It might be the diet

The colour and patterns in these spiders differ not only between separate individuals but also in the same individual over time, and there’s some suggestion that diet plays a role. 

Genetics is certainly a strong contributor though, and simple Mendelian inheritance explains why some patterns are more prevalent than others. But the diet may contribute to the quality of colour change over time. ³

6. They also want to know why

From the grinning clown face to the dappled black and red spotted abdomen, these patterns are a curious quirk of biology that has yet to be truly explained. 

If they aren’t used in mating much, they are likely to play a role in feeding, since those are really the two only behaviours nature cares about, but given the kind of predator the spider is, it might have something to do with the feeding of its own hunters. 

Certain birds use what’s called a search image, which is basically like when you’re looking for something in a packed cupboard and you try to picture it in your head so that it jumps out to fit the template. 

If the cumin had the ability to change its package colour every time you open the cupboard you’d spend a lot more time hunting for it, and this spider could benefit from a similar level of tomfoolery. 

7. This might be a family trait

This polymorphism is a selected trait in these spiders and shows up elsewhere in the family, too. So far it appears that this comes about convergently, and not from a shared trait between ancestral species, but the selective pressure that brings it about is still under investigation. 

One study shows that the more frequently occurring the morph, the less time it lasts before being eaten, and this would keep continuous pressure to keep releasing new paint jobs to avoid this. ⁴ 

Hawaiian Happy-face Spider Fact-File Summary

Scientific Classification

1. Rosemary G. Gillespie (1990), “Costs and Benefits of Brood Care in the Hawaiian Happy Face Spider Theridion grallator (Araneae, Theridiidae)”, JSTOR.
2. Geoff S. Oxford (2001), “Portraits of Evolution: Studies of Coloration in Hawaiian Spiders: The discrete color polymorphisms in spiders allow the study of evolution “in action””, Oxford Academic.
3. Rosemary G. Gillespie (1989), “Diet-Induced Color Change in the Hawaiian Happy-Face Spider Theridion grallator, (Araneae, Theridiidae)”, JSTOR.
4. Rosemary G Gillespie (1990), “Maintaining a happy face: stable colour polymorphism in the spider Theiridion grallator”, Heredity.