Common Pill Bug (Armadillidium vulgare)

It’s funny how sometimes the most common animals are the ones I know the least about. I know a fair bit about tenrecs, cheetahs and lyrebirds, but know next to nothing about pill-bugs. In fact, I’ve barely even thought about them, asides from when I played with them as a kid. But this blog is a place for people to learn about animals (me included), so let’s talk about pill-bugs!

Pill-bugs are crustaceans, like crabs and lobsters, and belong to the genus Armadillidium, which currently has 178 known species. That’s an awful lot of species to cover, so I’m going to focus on one of the most common, and the most studied, species: Armadillidium vulgare, otherwise known as the common pill-bug. Common pill-bugs originated in Europe, near the Mediterranean, but have since been introduced around the world, with particularly dense populations in the United States.

Pill-bugs require moist soil to survive, as they do not possess a waxy cuticle to prevent themselves from drying out. As well, pill-bugs breathe from psuedotrachea, a type of modified lung that must be moist to function. Humidity levels of around 50-60% or more are ideal for pill-bugs. They are most common in temperate or Mediterranean-like climates, and are often found under debris, such as logs, stones, or human waste.


I think pill-bugs are kind of cute, what do you think? Image credit: Franco Folini via Wikipedia

Common pill-bugs are oval shaped, and have armour-like plates along their bodies. They are not overly large, reaching sizes of 18 millimetres. Most pill-bugs are darkly coloured, with some having spots along their backs that can be yellow, brown or red. Common pill-bugs have seven pairs of legs, and a single pair of antennae.

Pill-bugs have to constantly worry about drying out, so much of their behaviour is centred around conserving moisture. When humidity is high, pill-bugs move slowly, and when humidity drops, they start to move more quickly, to search out moister areas. They move almost twice as much during the summer than in winter, and tend to be more active during the night, when moisture loss is reduced. When temperatures get to be 20 to 30 degrees celsius, pill-bugs release pheromones that cause them to bunch together, which reduces the surface area of individuals in the group, meaning less moisture is lost.

Many of you probably know that pill-bugs curl into balls, but do you know why? There are two likely reasons, the first being that all the soft, squishy parts of pill-bugs are located under their shells, so by curling into a ball pill-bugs can protect their vulnerable parts. The second is that rolling up into a ball helps prevent moisture loss, and as we’ve seen, moisture conservation is of paramount importance to these little guys.


A pill-bug unrolling from a defensive curl. Image credit: Franco Folini via Wikipedia 

Pill-bugs fall prey to a number of animals, including birds and arthropods. They are not entirely defenceless — in addition to their armour and their rolling-in-a-ball technique, pill-bugs can release nasty secretions when threatened. Unfortunately, pill-bugs’ defences only really work against small invertebrates, and birds will readily snatch these guys up. Also, a clever genus of ants have super long mandibles that can pry open a pill-bug when it’s curled in a ball.

Pill-bugs don’t have a particularly yummy diet — they feed on leaf litter and other decaying organic matter. They are, however, quite adaptable, able to survive for several months without food, and when food is scarce, readily switch to other sources of nutrients. Pill-bugs will eat the roots of plants, seeds, fruit, other pill bugs, and even their own poop.

pill bug

I had a lot of fun drawing this fella! 

The mating season in pill-bugs depends on the climate, with mating usually occurring in warmer times. Thus in regions with mild winters, mating can occur year round, while in other areas mating usually starts in the spring. Both male and female pill-bugs mate with multiple partners, and females can store sperm for up to a year. Pill-bugs moult regularly on a 29 day cycle, during which time the bugs cannot move or eat, and are extremely vulnerable. A special moulting cycle occurs in females, called the parturial moult. Mating can only occur during a female’s parturial moult, so males have to be prepared! Female pill-bugs retain their eggs in a pouch until they hatch, for about two to three months. The little pill-bugs stay in the pouch for a few days, and after moulting a few times, are independent from their mothers.

Hopefully by now you realize just how fascinating pill-bugs are, and have a greater appreciation for them. I certainly do! These are some awesome little insects (and they’re pretty cute!)

American Lobster (Homarus americanus)

I’ve never been much of a fan of lobster meat. I like it for the first few bites, especially dipped in butter, but then the meat gets way too rich and I get sick of it. While I might not be a fan of the meat, I do think lobsters are pretty cool animals, and it’s about time I wrote about them on here.

There are lots of different species of lobster, but I’m going to focus on the American lobster, as it is the species most people are probably familiar with. American lobsters live off the east coast of North America, from Labrador to North Carolina. They can be found in shallow or deep water, though they are more common in deeper areas. Lobsters like rocky areas, where there are lots of places for them to hide. They are nocturnal, spending the day inside their burrows, and coming out at night to feed.


The range of the American lobster. Image source: Wikipedia

American lobsters are the largest of all lobsters, and are also the owners of the title World’s Heaviest Arthropod. They can reach maximum lengths of 64 cm, and weigh over 20 kg. Most American lobsters are a greenish blue colour, but there are numerous colour morphs, such as bright blue, yellow, orange or albino. You might be familiar with bright red lobsters — but live lobsters are usually not that colour. The pigments that give lobsters their normal colour break down when they are boiled, resulting in the bright red, ready-to-eat colour.


A blue lobster. The chances of finding one are about one in two million. Image credit: Dan Dorothy via Wikipedia

American lobsters have ten legs, four pairs of which are small used for moving. The fifth pair are the most fun, extending into great big claws that are supposed to have the juiciest meat. You may not have noticed when you were digging into a lobster, but the two claws are asymmetrical. One is bigger than the other, and has rounded bumps; the smaller claw has sharp, small teeth. The functions of the two claws are quite different: one is used for crushing (the bigger claw), and the other is used for cutting.

Lobsters start out as very small animals, weighing less than a tenth of gram upon hatching. They grow through a series of moults, which begin with the lobster reabsorbing the minerals that harden the shell. This makes the shell soft, so that the lobster can break through it. The softness of the shell also allows the lobster to take in water, which makes it swell in size. The new shell then hardens, and the moult is complete. A lobster can grow 10-15% in size during each moult. To reach the minimum legal catch size, American lobsters go through 25-27 moults.

Moulting serves another very important function for lobsters: females can only mate within 48 hours of a moult. The females lay their eggs between a month and fifteen months after fertilization. during this time, sperm is stored inside the females, and the eggs are fertilized as they leave the females’ bodies. Lobsters can lay between 3,000 and 75,000 eggs, depending on their body size. After the eggs have been laid, female lobsters carry them under their tails until hatching, for about ten to eleven months. The survival rate of young lobsters is very small, with only one in one thousand reaching the juvenile stage.


A female lobster carrying eggs. Her tail is notched to mark her as a breeding female. Image source: Wikipedia

Though lobsters are a popular food animal, they are currently not threatened. This is in part due to the strict regulations that protect lobsters from overfishing. Lobsters under 8.3 cm must released, and in some areas lobsters over 13 cm cannot be caught, to keep breeding males alive. If a lobster is caught carrying eggs, a notch is put in her tail, and notched animals cannot be sold or caught. These regulations ensure a large breeding population, key to the survival of lobsters.

While there are many tragic stories about overfishing in our oceans, it seems like lobsters are doing pretty well, which is great news!


A fun silhouette I did of a lobster! 

Cover image source: Wikipedia

Arrow Crab (Stenorhynchus seticornis)

As regular readers of this blog probably know, I’m pretty terrified of spiders. Oddly enough, though, I have no problems at all with another group of eight-legged creatures. Crabs have never frightened me the same way spiders do, and there are three reasons I can think of why this is.

This first is that crabs don’t spin webs, so there’s no chance you’ll walk into a gross sticky web. The second is that unless your house is on the seashore, there’s a pretty slim chance you’ll stumble across across a crab in your house — you can basically choose whether or not you want to see crabs, by simply avoiding the beach. No such luck with spiders. And thirdly, the way crabs and spiders move is very different. Moving siders are enough to make me run screaming in the opposite direction, but I’ll likely follow a moving crab and probably try and pick it up.

Even if I was afraid of crabs, I probably wouldn’t be too scared of today’s animal, the arrow crab, because it really doesn’t look much like a crab at all. Arrow crabs are found in coral reefs in the Atlantic Ocean, at depths of 10 to 30 m. They are known to occur in the west from North Carolina to Brazil, and in the east around Cape Verde.

Stenorhynchus Seticornis

These crabs look so funny! Image source

Arrow crabs don’t grow very large, reaching lengths of only 3 to 6 cm. This only includes the crabs’ bodies, however, and not their legs, which are extremely long and thin, and can get to be 10 cm long. The most distinctive feature of arrow crabs is their long, pointed head, that has cool serrated edges. These crabs can be a lot of different colours, from golden to cream to yellow or brown, with black or iridescent stripes. Their claws are a beautiful bright blue.

Arrow crabs are active mostly at night, hiding under rocks and sea fans. They come out after dark to feed, and are quite territorial, especially with members of their own species. Arrow crabs scavenge whatever they can find, but will also hunt feather duster worms and other small coral animals.


A nice image showing the arrow crab’s blue feet. Image source

Reproduction in arrow crabs isn’t particularly exciting. Male crabs grab females and deposit spermatophores onto their abdomens, which the females can use to fertilize their eggs. The females carry their eggs on their abdomens until they hatch, at which point the larval crabs are on their own. The young crabs swim to the ocean surface, where they feed on plankton until they moult into their adult forms.

Arrow crabs are quite common in aquaria, and are used to control bristle worm populations. They are pretty neat looking, so I can definitely see the appeal of having one. Still, I’ve never had much of a desire to have an aquarium, so I don’t think I’ll be getting an arrow crab anytime soon.

Cover image credit: Nick Hobgood via Wikipedia

Sally Lightfoot Crab (Grapsus grapsus)

Most of the time when animals have funny names, it’s the common name of the animal that brings us amusement. The scientific names of animals are generally pretty boring and unintelligible. Today’s animal, the sally lightfoot crab, is an exception to this rule. Or so I thought it was. I originally read the animal’s name as “Graspus graspus” which would be a great name for a crab. About halfway through this post, I realized I had misread the name, and it is the far more boring “Grapsus grapsus”. After some quick research, I believe that grapsus comes from the Greek for crab, which means the sally lightfoot crab’s actual name means “crab crab”. So I guess it’s a little funny, but not exactly what I originally wanted.

My rambling aside, let’s talk about the actual animal! Sally lightfoot crabs are found in coastal areas in North and South America, and on islands from the Caribbean to the Galapagos. They like warmer areas, living in tropical and subtropical waters. The crabs will live in any areas with rocky shores, and usually stay at or above the spray line (the area above high tide that is usually not submerged in water).

These crabs are not particularly large, reaching between 5 to 8 cm in shell width. They are quite pretty crabs, being either bright red or yellow with fun black or green markings. Their feet are a nice cheery yellow and their claws are usually red. Young crabs are dark and blend in with the surrounding rocks.

Reproduction in sally lightfoot crabs occurs year round, with egg hatching occurring during full moons. Males compete for females by facing off with other males and doing a little “dance”. The crabs hold hands, then step left and right, presumably sizing each other up. If neither crab backs off, they will start fighting, which involves the crabs trying to break each others claws off. Sounds pretty nasty to me. Once males have won the right to mate, they deposit their sperm into females, who use what they need to fertilize their eggs and store the rest for later use.

Once their eggs are laid, females carry them on their bellies until the little crabs are ready to hatch. When the eggs are ready, female Lightfoot crabs helps them hatch by rubbing the eggs between their bodies and rough surfaces. The larvae hatch into the ocean where they swim out to deeper waters and begin to develop. Once they start looking like a crab, the young lightfoots make their way to the intertidal zone and start their adult lives. While they are still young, juvenile crabs tend to live in groups, while adult crabs are generally solitary.

Some young sally lightfoot crabs hanging out together.  Image source: Wikipedia

Some young sally lightfoot crabs hanging out together.
Image source: Wikipedia

Sally lightfoot crabs eat a wide variety of food, including sponges, molluscs, crustaceans, and small vertebrates. They have very strong feet which allow them to wander along the waterline looking for food without being washed away. These crabs have also been known to eat ticks off of live marine iguanas, helping the big reptiles be rid of parasites.

Although they weren’t named as wonderfully as I thought they were, I’m actually pretty impressed with sally lightfoot crabs. They are a pretty neat species.

Cover image source: Wikipedia