Hi everybody,

In the early days of mammal collections the dogma was that all you needed to archive was the skin and skull; the rest of the body was of little import. How wrong we were back then. The post-cranial mammalian body is bursting with stories. I wish I had a penny for every time a visiting researcher has asked whether we had post-cranial bones for a particular species and I've had to shake my head, only to see the disappointment and frustration in their eyes. Questions about how the animal eats, where it lives, to which other animals it is related, whether a particular human society hunted it, etc., are left hanging because mammalogists discarded the post-cranial carcass in days of old. Today, we save everything we can from a given specimen. We do this for both the questions we know this material will answer, and the questions yet to originate.

In my last dispatch I told you about what we do to preserve a mammalian skin. How do we clean the skeleton? We basically have two choices...

If the skeleton is large enough, we can boil it. We typically cut the carcass into manageable sections, place these sections into cloth bags and put them into one of two large industrial-size kettles that are steam-jacketed. We fill the kettle with water, turn on the steam, and the water heats to boiling, cooking the specimen. The result is not unlike what happens to the chicken bone or ham hock you put in your soup...with enough boiling the meat starts to fall away from the bone. After a few hours of boiling, we turn off the steam and let the contents cool, very gradually. We are extremely concerned about the time it takes to cool the specimen, because if the bones cool too quickly they may develop cracks. Once the contents are cool, we lift the bags out of the kettle, rinse the bones in water, and allow the bones to dry gradually. Again the length of drying time is important because of the problem of cracking.

Frequently, we use a modification of the above technique. We put the carcass into the kettle of water, but we do not turn the steam on...we just let the carcass rot! I am certain that you all can imagine the disadvantage to this procedure. It stinks. No, it REALLY stinks! Let me tell you just how bad it stinks...

I started working at The Field Museum in 1989. After being here a week, I was still exploring new places I had not yet seen. One day I found myself in the kettle room, and decided to see what was in the smaller of the two kettles, I lifted the stainless steel lid and found the right forelimb of an Equus burchelli sticking out of a 2-inch thick carpet of undulating maggots. Months previously, someone had started processing a zebra that had died at the zoo and forgotten about it after placing the post-cranial elements in the kettle. The stench emanating from this mix was enough to singe your eyebrows. The hoof was falling away from the distal phalanx so I knew it had been in the kettle way too long and needed to come out immediately. So I lifted the bag of bones from the broth of rot and started to rinse the bones with water. What I did not realize, however, was that there is a vent in the corner of our kettle room that, due to some design flaw, sucks the air from the kettle room and merrily pumps it into Stanley Field Hall, the main public lobby of the Museum.

Now, as luck would have it, I was doing this at about 8 pm at night, and concurrently there happened to be a huge party in Stanley Field Hall. I did not witness this, but evidently the party goers made a mad rush to any exit they could find as a green, physically palpable wall of putrid stink migrated down Stanley Field Hall pushing every living organism along in front of it. I learned a very valuable lesson that night; every time we use the maceration technique (a technical term for rotting) we ask our engineers to turn off the vent in the corner of the kettle room!

Now, because of the stress that macerating, or boiling, exerts on bones and teeth (cracking of bone, teeth coming out of the skull), not to mention our co-workers, we use a more ingenious technique to clean our skeletons whenever possible. We employ hundreds of thousands of beetles to eat the tissue from the bones. Not just any beetle, however; we use Dermestes vulpinus. This insect is also known as the leather beetle or carrion beetle, or just plain dermestid, and is a member of the Dermestidae, a family of beetles that are a very common household inhabitant. You might have them crawling on your carpet even as you read these words. They eat wool, adhesive book bindings, and lots of other organic materials. In the late 1800's the French discovered that dermestids were very effective skeleton cleaners. The method was adapted in other museums and today, I can say "dermestid" to a worker in any large natural history museum in the world and would be understood immediately.

The reason we like these beetles so much is because they can render the dried carcass of a mouse into a clean skeleton within a matter of hours. A raccoon might take a week. This is basically free labor for us: no unions, no coffee breaks, no pay raises. We give them a free meal and they give us a clean skeleton. They live their entire lives in our "bug colonies" - old fish aquaria with screened lids. It is the beetle larvae that do most of the feeding and, because they are very tiny to begin with, they get into every nook and cranny of the skeleton, eating all the muscle tissue they can find. The larvae molt about 6-7 times, eventually turning into adults, who reproduce, lay eggs and the cycle continues. It's a wonderful arrangement, except...

If these same beetles were to escape from the room in which we house them they could destroy many aspects of the collection within The Field Museum, including not only mammal skins, but bird mounts, butterflies, and textiles (remember what I said about what the family eats). For this reason, we keep the beetles in aquaria with tightly sealed lids and these are housed in a special room with double doors separating this "bug room" from the rest of the prep lab. We also freeze any bones that we have taken out of the aquaria for 24 hours before they leave the bug room. The freezing kills any potential "stowaways" that might be hiding in the various foramina of bones that we bring out of the bug room.

Hogwash, you say? Nonsense, you exclaim? Check out The Bug Cam on the expedition site under Video Reports. You will see a shrew skeleton being cleaned from the time it was put in the beetle colony at 7 pm one evening until 9:30 am the next morning. Enjoy!

Cheers,