A Molting Tarantula

Last week, one of our Chilean rose tarantulas (Grammostola rosea) molted. This event is one of the most dramatic non-emergencies an Animal Caretaker is apt to encounter. In fact, the process is so stressful looking, it's common to confuse a molting tarantula with a sick or dying one. Often it’s hard not to intervene and 'help'.



Prior to molting, a tarantula builds a silk nest and lies down on her back in the middle of it. She appears to be in her death throes, but then with almost impossible effort, she bursts her way out of the old skin, revealing a velvety, fresh new spider underneath.

The picture above shows our spider, Roslyn, (on the left) immediately after she freed herself of her old skin. She is waiting for her legs to fully expand. Every few minutes she stretches all the legs on one side or the other, probably as she pumps fluids into them to fill out her skin.

For several hours after molting, the spider is totally helpless. Her new exoskeleton needs to expand and harden. Since spiders usually support their full weight on their legs, this is a problem; her legs are too weak to support her body. The tarantula must stay on her back until her legs are strong enough to support her body.

The lighter colored form, on the right, is Roslyn's old skin, lying empty beside her.

In related arachnid news, a newly discovered species of tarantula from the Amazon has been named after a Beatle. Imagine!


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Book Lungs?

Many people view Animal Care husbandry as simply a series of housekeeping/critter-feeding chores. And in fact, that is an essential part of our jobs. However, observation of animal behavior is critical to learning how to keep our creatures healthy and happy. Sometimes animal observations are too good to keep to one’s self.

Recently, Life Science Manager Sarah Moore experienced one such observation. Please note the addendum.




Today as I was removing a black widow spider that has passed on, and feeding the ones that were still alive, I noticed the scorpion moving around restlessly in the cage.

On its underside, I saw what looked for all the world like wings – two pale symmetrical structures with many fine plate-like subunits.


I was fairly sure this was the scorpions’ respiratory system, called “book lungs” because they act like lungs and are made of many thin pieces stuck together, like pages in a book. But they were so weird I had second thoughts. Often when something weird is sticking out of the underside of an animal, this means S-E-X. After all, reproductive organs come out to play, and then get stored away again. A lung that stayed out in plain view seems very vulnerable to the elements.

So I double-checked, and I was right the first time! Those things were its book lungs, and they were just as they should be.


Book lungs are a fascinating example of convergent evolution. They appear to have evolved separately in spiders and scorpions as each became terrestrial. Their common ancestor was aquatic, resembled a horseshoe crab, and had book gills, which were a very similar organ for gathering oxygen from water. And like our own lungs, both are a great way to maximize surface area for oxygen exchange in a fairly small body part.

Addendum: As it turned out, I was right to second guess my first guess. The book lungs are more internal. What we were looking at was the scorpion’s pectines. These are a sensory organ that seems to be used by the male to detect pheromones produced by the female. While it is not fully understood it’s pretty clear my second idea was much nearer the mark.

We did our best to snap photos of the scorpion displaying its book lungs pectines. An annotated view of scorpion anatomy can be found here: http://www.ntnu.no/ub/scorpion-files/scorpion_anatomy2.jpg



The very next day, Animal Care Lead Lauren Bloomenthal caught our Chilean Rose Tarantula showing off her book lungs. Or is there something in the air or is this just another case of the power of observation - as when you buy a red car you suddenly see red cars everywhere?

The next time you visit Pacific Science Center check out the residents in our Insect Village. Let us know what interesting animal behavior you observe.

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Seattle Bug Safari

Seattle Bug Safari, the wonderful arthropod museum located in Pike Place Market, recently closed their doors. Because of the closure, their fantastic variety of exhibit animals needed to find new homes.

Many of the species exhibited are animals regulated and could only go to permitted owners. Fortunately, Pacific Science Center holds those permits. So last month, Animal Caretakers Sarah, Chris, and Lauren went on an adventure to pick up some new arthropods for Animal Care.

We loaded up on boxes and containers to hold our new friends, hopped on the monorail, and headed down to Pike Place. When we got there, owner Brian Rolf brought us in to look over the selection. We knew we had to fight the “kid in a candy store” syndrome; mainly take creatures that we already exhibit and/or have the space and resources for. With that in mind, we packed up the following:

1 Chilean Rose Tarantula
9 Blue Death-feigning Beetles
4 Diving Beetles
4 Cactus Longhorn Beetles
6 Giant Brazilian Cockroaches
57 Australian Prickly Sticks

Most of the animals joined others of their species on exhibit. Australian Prickly Sticks, a species we have had in the past, are now on display. In addition to the Prickly Stick adults and juveniles on exhibit, we have numerous containers of their eggs hatching in an off-exhibit nursery. The young Prickly Sticks can grow up in the quiet of the back room with lots of blackberry leaves to enjoy. After a few molts, they will be placed on display.

Thanks to Brian and Seattle Bug Safari for some amazing new animals! Watch Brian showing his knowledge and insect handling skills here: http://www.king5.com/new-day-northwest/Seattle-Bug-Safari-Invades-the-New-Day-Northwest-Studio-89542582.html. Do you recognize some of the arthropods we also have at Pacific Science Center? Come by and visit them!

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Rosie the Riveting

Last week we received a frantic report from Pacific Science Center’s Science Interpretation Department. Rosie, our beloved Chilean Rose-Hair Tarantula was dead! When asked how they knew she was dead, the observer reported that she was upside down, with all eight of her legs sticking straight up into the air. Obviously she must be dead, right? Right?



We’ll share the good news first. Rosie was not dead. She was getting ready to molt. Like other arthropods, tarantulas molt, or shed, their exoskeleton as they grow. As an adult, Rosie will usually molt about once a year. Younger tarantulas molt much more frequently to accommodate their rapid growth.

The Life Sciences department was actually anticipating molting activity from Rosie. We had noticed a few months ago that her color was getting dark and dull, and the hairs on her abdomen were becoming sparser. When tarantulas are ready to molt, they usually prefer to be in a dark, moist, and safe habitat. Because we noticed that Rosie was at this stage, we decided to move her off exhibit to give her more privacy.


This move worked well because it was just at the same time that we were gearing up for the Goosebumps exhibit and we had just acquired a second tarantula that could take her place. So Carmen, the beautiful new tarantula, went out into the Insect Village while Rosie took her time in the back. We had hoped she would molt before the Goosebumps exhibit opened, but she just wasn’t ready yet. When the exhibit opened, we set her up in a new cage and offered her extra heat and an enclosed burrow for whenever she decided she was ready.


Finally the day came that she flipped herself upside down, a telltale sign that a spider is about to molt, but also a possible indication that a spider is dead. This is an extremely delicate and dangerous time for a spider, so we couldn’t probe her to make sure she was alive. All we could do was cross our fingers and hope for the best. Sure enough, when we came in the next morning, we found a beautiful new Rosie. She’s back to her pretty rose color for which she was named, and she’s flush with healthy hair. In fact, she’s so beautiful now, she’s giving Carmen a run for her money.



Come see Rosie and some of her other spooky (but beautiful friends) for a limited time in the Goosebumps exhibit. There’s nothing to be scared of!



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The Fearsome Threesome!

With the Goose Bumps! The Science of Fear exhibit now open, fans of Pacific Science Center’s arthropods will have another place to visit with some of their favorite animals. People who have avoided our Insect Village due to a dislike of bugs now have a chance to rethink their feelings. Three species are featured in the exhibit in ways that encourage our guests to explore and challenge their fear of bugs.

The species we chose reflect the reactions we sometimes hear from our guests, as well as the fears of some of our own staff.



Many people have a deep, some say innate, fear of spiders. The Chilean Rose Tarantula (Grammostola rosea) is a calm species of spider. They would rather avoid trouble than face it. When threatened, they are more likely to attack by shooting leg hairs, causing skin irritation, than they are to bite. Even if provoked to bite, their venom is not dangerous to humans. Our tarantula is nearing time to shed her skin, something tarantulas only do once each year. Her exoskeleton is balding right now; soon she will have a new, silky growth of pink hair. She prepares by building herself a nice, comfortable silk pad to lie down on. Her species doesn’t like to touch rough surfaces.


Fear of cockroaches is fairly common. Most people don’t specifically fear being harmed by them, but rather dislike the idea of having them in the home. The Madagascar Hissing Cockroach’s (Gromphadorhina portentosa) natural habitat is the outdoors, which may make them less threatening. They are familiar from popular culture, and are also the one insect Pacific Science Center invites our guests to touch. Touching butterflies can hurt their wings, but cockroaches’ reputation for robust good health is deserved – they can be held and pet by hundreds and remain unharmed. But save the hand sanitizer for after you’ve pet them. It contains ingredients that dry their skin, and is much more of a threat to them, than they are to us.


The Desert Centipede (Scolopendra sp) was chosen for this exhibit because our Life Sciences Manager, Sarah Moore, admits that it is the one invertebrate she fears the most. This centipede can deal a painful bite and is larger than your garden variety. It is also far more mobile than most venomous creatures, running after its prey and catching it with its fangs. But in truth, Sarah’s fear is out of proportion to the damage this arthropod can inflict. Unless one had specific allergies, a bite would hurt but do no lasting harm. Active predators, centipedes are one of the beneficial animals that help keep pest insect populations under control. Without centipedes, spiders, and other carnivorous arthropods, we would have more damage to our gardens and more bugs in our houses!

What insects or arthropods do you fear? What makes them scary? What would make them less scary?


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