I fear that the 2000s and 2010s will be looked back on as the dark age of spider collecting for taxonomy and systematics. Traditionally, researchers discovering and archiving specimens of spiders have used 70% to 80% ethanol for preservation, as it’s strong enough to ensure no decay, but has enough water that the bodies retain some flexibility. If higher concentration ethanol is used (95% to 100%) the bodies become brittle, and are likely to break when examined. Also, they tend to be distorted, as their legs can collapse as their water is drawn out quickly. For morphological study, it’s pretty clear that 70-80% ethanol is better for spiders.
But for molecular studies, the 20% to 30% water has been a real problem, because it degrades the DNA. For this reason many spider researchers (including myself) have collected most of their material over the last two decades in 95%. Good for DNA, not so great for morphology, though marginally acceptable.
An example of the perils of 95% ethanol: In 2007 I was collecting in Gabon, and had many beautiful specimens from Monts de Cristal preserved in 95% ethanol. Our next site was a harrowing 50+km drive down a rain-gullied dirt road. We held on for our dear lives (literally) as we were tossed around in the back of the pickup truck bouncing down the road at 40 to 80 km/hr. The little pickled spiders in their vials had nothing to hold on to, and when we arrived I found that they were floating in a soup of their own setae (hairs). Many of the spiders were bald because the 95% ethanol robbed the bases of their setae of flexibility, and being brittle, they just snapped off.
Such are the costs of doing molecular phylogenetics, and 95% ethanol preservation seemed worth the cost to be able to gather this vital source of phylogenetic information.
But, with molecular methods improving, we will soon come to the point where a specimen in 80% ethanol can yield good enough DNA data easily enough that the tradeoff no longer favours 95%. We will go back to preserving in 80% ethanol.
And so, I imagine this conversation in 2050:
Student: I’d like to study thiratoscirtine jumping spiders. Where should I start?
Professor: Best to start studying Mbuta’s material from the 2030s. There’s also some good material in Tervuren from the 1990s.
Student: But why not start with the large amount of Gabonese material collected by Maddison in the 2000s?
Professor: Work on that last. It’s not in good condition. It was preserved in 95% ethanol.
Student: 95% ethanol!!!! How awful! Why?
Professor: Sigh. Let me tell you a story about how gene sequencing used to be done….