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My world has a variety of creatures which evolved from arthropod-like ancestors and became more similar to vertebrates in many aspects despite still having exoskeletons. One of these creatures, as I envisioned them, is a 6-legged predator no bigger than 30 cm long and strongly inspired by mole crickets, being a capable digger while still being able to fly.

cutting to the chase, the simplest explanation for why they need to be able to both fly and dig is that I'd like them to be able to both fly and dig.

My main problem when designing this creature's anatomy however is centered around 2 main "issues":

  • Rather than classic insect wings, my creature has membranous wings evolved from the first pair of limbs, counting from the head, and has somewhat long limbs.

  • I'd prefer to leave the other 2 pairs of limbs closer to its back adapted mostly for grappling prey and moving through the soil, as I'd like to stray from a design that's too "dragon-like" as much as possible, meaning a body plan that involves the frontal limbs being adapted to dig and the middle pair for flight is something I'd like to avoid, especially since I failed to find a way to make them "retractable".

Now the problem with such preferences is that I've met a point of contradiction: a creature highly adapted for burrowing have somewhat short limbs and powerful shovel-like forelimbs, while a flying vertebrate often has powerful, but proportionally longer forelimbs which tend to engage in a motion that's fairly different.

I tried searching for other real-world burrowing creatures that could help me flush out the anatomy of my creature, but other than the mole cricket, the closest examples of animals that are still capable fliers while still being highly adapted to burrow through the ground were the burrowing owl, which is itself anything but adapted for digging, merely altering existing burrows with its claws and beak most of the time, and the new Zealand short-tailed bat, of which I found very little regarding their ability to dig. As for the multi-use of wing-like limbs, the best examples were vampire bats, the burrowing bat and pterosaurs, which as far as I researched do not include any known species that's good at burrowing.

As for alternative methods of digging, creatures that don't use their limbs to dig, as far as I found, were comparatively much slower at digging through the ground, making such options less than ideal for my predator.

With that out of the way: what are the limits of adapting limbs with membranous wings for burrowing without completely compromising the ability to fly? Shorter wings are certainly an option I already considered, but I couldn't find anything regarding adapting the wings to also be used in digging. The wing limbs have 3 digits that can be adapted into a more shovel-like configuration, and it can tuck its membrane closely to the body to prevent damage while moving on the ground. If it matters, the overall structure of the limb and how it works is very similar to a vampire bat's, if it had 3 thumbs instead of one and used an exoskeleton.

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  • $\begingroup$ Might want to look at beetles. $\endgroup$ Mar 2 at 19:16
  • $\begingroup$ @GaultDrakkor kinda hard, since their wings aren't exactly what I'm looking for. Thanks for the suggestion regardless. $\endgroup$ Mar 2 at 22:23

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At least one kind of terrestrial bat can burrow

The two mystacinid bats, named the Greater (Mystacina robusta) and Lesser (M. tuberculate) Short-tailed Bats, are the most terrestrial of all the 950 or so bat species in the world. They spend much time at night running up tree trunks and along branches or burrowing in the leaf-litter and humus on the forest floor searching for food. They also burrow into rotten logs and trees to excavate their own roosts or use seabird burrows as both roosts and feeding sites. This "un-batlike" behavior is possible because they have a unique method of folding their delicate wings to protect them from injury. They are able to walk on their robust hind legs and feet, using their fore arms as front legs. Their fur is short and velvet-like, similar to that of moles and shrews. This terrestrial behavior probably evolved over millions of years because of the complete absence of mammalian predators. (Source)

And that quote helps you a lot.

  • The bats learned to fold their wings to protect them.
  • They learned to use their hind legs (I assume to help push them during burrowing and removing litter).
  • Their fur is more conducive to burrowing.

But it also gives you limitations:

  • They burrow in leaf-litter and humus on the forest floor.
  • They burrow into rotten logs and trees (I assume "rotten logs and rotten trees").
  • They burrow into other creature's dens.

What this tells me is that you could have the following limitations:

To protect the membranous wing your creature would believably burrow only in soft soils, like sand, peat, or loosely compacted sediments. Rocky soil would be right out. They would be unlikely to burrow deeply unless your design toughened the wings and the bone structures of the arm, but do that too much and you begin compromising flight. I could imagine that they would burrow into the dirt surrounding tree roots to take advantage of the root structure's ability to add to the purpose of the den.

But what I like the most is that your creature is a predator. This means that the burrowing ability can be used to chase food. additional limits would be the need to dig a short distance very quickly before the prey runs deeper into its den and to avoid the need to move litter aside. I would think this creature would favor chasing prey larger than itself so that it's burrowing ability allowed it to move faster without depending on the need to significantly (if at all) widen the hole. Just a thought.

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  • $\begingroup$ Yes, this is basically what I was looking for. Thanks a lot. $\endgroup$ Mar 4 at 23:59

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