Comments on: Building Bigger Bugs

By: Athena Andreadis

Athena Andreadis — Mon, 08 Nov 2010 19:46:44 +0000

As far as I know, the largest recorded spider size was ~15 inches, measuring the fully extended leg span. I know that adversaries can loom a lot larger when you’re in full fight-or-flight mode, but 6 feet in diameter is completely out of the question for a contemporary insect, though it’s about right for Tolkien’s Shelob.

By: Amanda Barrett

Amanda Barrett — Mon, 08 Nov 2010 15:46:25 +0000

It’s certainly possible. There is a ton of insect diversity covering a wide range of sizes. The study that I referenced was specifically looking at beetles, which didn’t actually exist during the Carboniferous period. They found that at the rate the beetle tracheal system increased in size, the beetle could not grow larger than 6 inches…which is the approximate size of the world’s largest known beetle, Titanus giganteus. Other insects may have a much more flexible tracheal system that is less restrictive of their growth.
Also, even if the modern atmosphere had a higher oxygen concentration it doesn’t necessarily mean that insects would start growing larger. There are other environmental factors in play, which may select for a smaller size. In places where a larger size is more advantageous, it makes sense that certain insects would have an adapted tracheal system to support that growth.

By: Korollocke

Korollocke — Mon, 08 Nov 2010 01:39:13 +0000

I think your theory has a few holes it. I’ve seen spiders that are the stuff of nightmares in the deep woods during my logger days. Roughly 5-6 feet in diameter. probablly due to a high oxygen level because of all the trees plus no shortage of chow either. Also big spiders in Africa also, again high oxygen levels. In Montana there are giant dragon fly’s referred to as snake doctors there 9-10 inches long, hairy and brightly colored and make a loud clicking sound as they fly through the woods.

By: Peggy

Peggy — Fri, 05 Nov 2010 23:18:17 +0000

Just the idea of a tarantula farm makes me shudder.

By: Athena Andreadis

Athena Andreadis — Fri, 05 Nov 2010 22:19:57 +0000

Non-myelinated neurons limit insects to linear conduction, which circumscribes size unless you get huge-diameter neurons (which occur in giant squid and are the reason why they’re used in electrophysiology). Also, the surface area-to-volume ratio problem is more extreme with exoskeletals than endoskeletals.

By: jwbjerk

jwbjerk — Fri, 05 Nov 2010 20:19:00 +0000

OK, let’s say that we can magically swap out insect respiration with a tetrapod lung — i.e. something that could theoretically provide enough oxygen for sauropods and whales.

So how big could insects get before something *else* was a limiting factor — like their diffuse circulation, or the weight of their exoskeleton?

By: Athena Andreadis

Athena Andreadis — Fri, 05 Nov 2010 15:59:19 +0000

I knew about the transgenic goats but one thing that makes spider silk so light yet so strong is the process it undergoes in the spinnerets. That establishes a polymerization gradient that is decisive for the final outcome (that’s why different types of spider silks exist, and why different spider species produce different silk). The process is not a mystery, just as gestation is not a mystery. As always, the devil’s in the details.

By: Casey Seda

Casey Seda — Fri, 05 Nov 2010 15:30:59 +0000

Actually, goats have already been transgenically engineered to produce spider silk proteins in their milk over 10 years ago. The scientists that have produced these goats are currently trying to place the same genes responsable for silk into alfalfa to increase the production scale.

By: Athena Andreadis

Athena Andreadis — Fri, 05 Nov 2010 15:29:50 +0000

A fuzzy pet that you can sic on enemies AND use as a money engine? Sounds close to ideal.

By: Zarpaulus

Zarpaulus — Fri, 05 Nov 2010 15:09:21 +0000

Why not engineer tarantulas for increased silk production, people keep those as pets you know.