Analogy of the week
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From Dan Fagin, "We Can Now Track Individual Monarch Butterflies. It’s a Revelation.", NYT :
For the first time, scientists are tracking the migration of monarch butterflies across much of North America […]
The breakthrough is the result of a tiny solar-powered radio tag that weighs just 60 milligrams and sells for $200. […]
Most monarchs weigh 500 to 600 milligrams, so each tag-bearing migrator making the transcontinental journey is, by weight, equivalent to a half-raisin carrying three uncooked grains of rice.
Rick Rubenstein, who sent in the link, commented
I suppose "uncooked grains of rice" has some merit, but "half-raisin"? Who has an intuitive sense of the weight of half a raisin? And there's something very funny about the use of "carrying" — how, and why, is this half-raisin carrying these rice grains? Is this supposed to be a relatable experience?
In defense of Dan Fagin, I can only note that the analogy caught Rick's attention and will probably stay in his memory.
I would have thought that a butterfly weighed more than half a raisin, and maybe it would, depending on the size of the raisin. This site gives a raisin weight estimate of about 1/3 to 1/2 gram, suggesting that a butterfly weighing "500 to 600 milligrams" would actually weigh as much as one or even two raisins. I'll leave it to readers to evaluate the relation of "three uncooked grains of rice" to a 60 milligram radio tag.
Jerry Packard said,
November 18, 2025 @ 8:06 am
True, the analogy is not helpful. My question is: how much will a chip weighing more than one-tenth the body weight of the butterfly hinder it in its journey?
J.W. Brewer said,
November 18, 2025 @ 8:09 am
There's a longstanding genre of explanatory analogies offered to pregnant women and other expectant parents of the form "at X weeks the baby is the size of a Y," for what you might call "grocery-store" values of Y. One such set of analogies current 25 years ago when my oldest child was in utero had, if memory serves, both a "size of a grain of rice" and a "size of a raisin" stage of fetal growth. Googling suggests that most current sets have alas abandoned those comparators and you would need to figure out how to map them onto a current sequence that e.g. goes (at around those sizes) sesame seed -> lentil -> blueberry.
That said, the weirdness here is more the mixing of the two different grocery-store analogies into a single incongruous image, not either analogy on its own. Since twins generally develop at the same pace that sort of incongruity wouldn't tend to arise in the pregnancy context, unless you were doing a synchronic comparison between two pregnant women who had conceived at different times so you had one at the size-of-an-olive stage next to another at the size-of-a-lime one.
Stephen Goranson said,
November 18, 2025 @ 8:25 am
Similarly to Jerry, when I read that NYT story, I thought that it was not only a burden, maybe even deadly, to the butterfly, but it also could affect–observer effect?–the flight, skew the data.
Ross Presser said,
November 18, 2025 @ 9:19 am
An animated short on Saturday morning TV in the 1970s introducing the metric system to US kids had the lyric "the gram – about the weight of a single raisin. About the weight of a paper clip, now isn't that amazin'!"
So half a raisin might be an inaccurate estimate for 500g, but it has roots in pop culture at least.
Seonachan said,
November 18, 2025 @ 11:26 am
How many grains of rice can dance on the head of a half of a raisin?
KeithB said,
November 18, 2025 @ 3:03 pm
Yeah, I would say that half a raisin is a poor estimate for 500 grams.
It is probably 500% lower if I have my Trump math right.
JPL said,
November 18, 2025 @ 5:23 pm
The strength of ants is known to be Herculean; is the same true for butterflies? (It doesn't look like the author was making an analogy, but rather suggesting an equivalence (of weight) between the objects. (The image of a half-raisin carrying three grains of rice is Mr Rubenstein's contribution.))
Roscoe said,
November 18, 2025 @ 7:24 pm
An African raisin, or a European raisin?
JPL said,
November 19, 2025 @ 1:06 am
I think what we're talking about is a sultana probably.
Stephen Goranson said,
November 19, 2025 @ 8:40 am
For a long flight, 10% added body weight seems not negligible.
And an attached solar radio gizmo doesn't interfere with the antennae?
…hum-bug
ajay said,
November 20, 2025 @ 8:49 am
And an attached solar radio gizmo doesn't interfere with the antennae?
…these are insect antennae, not radio antennae. :)
For a long flight, 10% added body weight seems not negligible.
It is heavy. The rule of thumb for the larger tags used for migrating birds is 5% maximum, and ideally you should be aiming for 3% or less.
Rather than providing traffic to the NYT, here's the actual announcement: https://celltracktech.com/pages/project-monarch-press-release-november-17-2025
The project doesn't provide an average weight, and the NYT seems to have made up their figure of 500-600mg. The Forest Service says up to 750mg. But that still means the tag is 8% of body weight for a large adult.
Philip Taylor said,
November 20, 2025 @ 10:28 am
I think one might ask "what effect would an additional payload of 8% have on the distance achievable on a full tank of fuel for a fully-laden jet aircraft ?". While by no means directly comparable, it might at least offer some idea on the potential effect on butterflies …
Gregory Kusnick said,
November 20, 2025 @ 12:03 pm
Coming at the question from a linguistic angle, I want to suggest that the fact that we use the same word — flying — for what butterflies do, what birds do, and what jet planes do has perhaps tricked us into thinking that excess weight must affect them all similarly, despite radically different modes of propulsion and orders of magnitude differences in scale.
Insects are small enough that air friction and viscosity matter much more than weight. Their method of locomotion through the air might better be described as swimming or rowing rather than flying; their wings are more like oars than like airfoils. So maybe we should be making analogies with fish or boats instead of birds and jets.
Peter Taylor said,
November 20, 2025 @ 2:46 pm
I have just weighed 10 moscatel raisins at 11.23g for an average of 1.123g; and 10 sultanas at 4.41g for an average of 441mg; so half a moscatel raisin is about right for 500-600mg.
Benjamin E. Orsatti said,
November 21, 2025 @ 8:09 am
lolololololololololololol
So, 14 comments into a post among humanities-types about how much a raisin weighs, somebody finally gets around to weighing some raisins. The CMU / MIT crowd would find this hysterical.
(sorry, _somebody_ had to say it)
Victor Mair said,
November 21, 2025 @ 8:55 am
@Benjamin E. Orsatti
The CMU / MIT crowd would find this hysterical.
This is LL.