Science From Home update: a moth infestation

Here's an update toa story from April 2020about scientists who had brought their science home with them during lockdown. When we last spoke to insect ecologist Zenobia Lewis, she had taken about 800 moths and stored them in her downstairs bathroom, effectively bringing home her whole lab. You might be able to guess what happened next. Phil Sansom caught up with Zenobia…

Zenobia - It's been an interesting few months, Phil, I have to say. For the first few weeks or months it was great not having to commute to work; I've got my experimental moths literally three metres from where I usually sit. And then they invaded my house. This species, the Indian meal moth, are well known for just being a disaster for working on because they are so hardy and they're so good at invading things; but I'll be perfectly honest, that day when I walked into the lab and there was just hundreds of moths all over the ceiling of the room, I had to close the door, sit down, pour a glass of wine, and calm myself before I could go back in there!

Phil - How bad was it in the end?

Zenobia -
It was pretty bad for a reasonable length of time; I think two months maybe. I was having to go in and do a sweep every single day, and there would be somewhere between 50 and 200 moths somewhere in the room. If that wasn't bad enough, they also contaminated their own food supply.

Phil - As in they pooed in it?

Zenobia - No, they laid eggs in it.

Phil - Oh!

Zenobia - And so these rogue moths were eating the food supply that I was using to keep the lines alive. We literally had moths coming out of the woodwork for weeks. I think we've largely controlled it now, and we've got it down to a handful of adult moths appearing each night.

Phil - Is there any silver lining here?

Zenobia - Our plan is to examine some of their traits, like body size, and compare to some historic data that we've got, and see what this period of stress has done to them. Because it has been stress: they've been in fluctuating temperatures; they haven't had their densities controlled, which is something that we usually do; they haven't been getting standardised amounts of food. And we'd like to see what that has done to them.

Phil - I don't know how long a moth lives for. Are they the same exact moths that were there at the start of the pandemic? Or is this a new generation?

Zenobia - It's been several generations since they first came home, but because they'd been at a lower temperature, and also fluctuating temperatures, it's massively stretched their development period - well, the whole of their life cycle really. Rather than four to five weeks to go through their life cycle it's been taking them two to three months, which is a massive change.

Phil - Okay. If you had to put a guess or a hypothesis on it, would you say that the stress might've made them smaller?

Zenobia - That's also an interesting question. Usually the longer they take to develop the bigger they are, literally just because they've got more time to eat. And so in contrast to what you would expect - given they've been in pretty weird conditions - they are much, much larger than they would usually be, because they're taking so long to develop.