Wikipedia:Reference desk/Archives/Science/2016 August 23

= August 23 =

Overview of true flies mimicking wasps and bees
Hoverflies are known for mimicking powerful hymenoptera like wasps and bees. But they are not the only true flies doing so. Other examples include several soldier fly species. Two questions: Beetles, butterflies etc. using this mimicry are not included the question. --KnightMove (talk) 15:29, 23 August 2016 (UTC)
 * 1) Can an overview be given which fly families include hymenoptera-mimicking species?
 * 2) Would a layman, not familiar with the specific species, call such a mimicking fly probably a "hoverfly", even if it does not belong to this family?


 * The Bombyliidae fit the bill. Mikenorton (talk) 15:45, 23 August 2016 (UTC)


 * In my experience, laymen don't often know the word or concept "hoverfly". If they do, then sure, they may well apply it to bee-looking flies outside the Syrphidae. But some people use the common name drone fly, some may use the term bee fly to pseudo-incorrectly refer to a Syrphid, etc.
 * Acroceridae is another Dipteran family with some bee mimics, as is Asilidae. Together with they Bombyliidae Mike mentions and the Syrphidae you mention, I think that covers all the mimics that I already knew about. Here is an interesting article on behavioral mimicry of honey bees in some Syrphidae spp. . Here is an article that discusses a few different bee mimics, and looks at their relative similarity, frequency, and potential benefits. This paper  discusses some of the interplay between bees, their mimics, phenology, and birds. I am unable to find a list of Dipteran families in which presumed hypmenopteran mimics occur. SemanticMantis (talk) 21:36, 23 August 2016 (UTC)
 * Well, I thought that picture was a hoverfly, until I looked it up, so I suppose that's one instance of someone calling such a mimicking fly probably a "hoverfly". I suppose it would depend on how similar the non-hoverfly mimics were to hoverflies (unlike the one here, the pictures on the soldier fly page don't look much like hoverflies to me).  Then there's behaviour - hover flies hover, hence the name.  Do soldier files and other mimics also hover?  If so, I expect a lot of people would mistake them for hoverflies.  If not, well, maybe fewer would. Iapetus (talk) 11:39, 24 August 2016 (UTC)
 * By now I should clarify the motivation for my question. In my native language German, pretty much all such flies are called hoverflies ("Schwebfliegen" in German, which is both the factual and literal translation), unless there is an established term for a single species (Drone flies are usually called Mistbiene, "dung bee"). Somewhat prematurely, I've assumed this will be the same in English.
 * I do not know whether all hoverflies always "hover" when flying, and whether this can always be recognized clearly. Once I've seen a bumblebee-mimicking fly in the forests, humming loudly in flight. I do not know for sure whether it was a hoverfly (but quite sure it was, very possibly a Volucella bombylans). However, I would not have regarded its flight as "hovering". Anyway, you might catch a wasp-mimicking fly sitting on a flower or somewhere else; and even in flight, you hardly would regard a non-hovering-but-wasp-mimicking fly as non-hoverfly.
 * This image of a wasp-mimicking-non-hoverfly was my very motivation for asking, as I had not been aware of the existence of such flies. --KnightMove (talk) 10:51, 25 August 2016 (UTC)
 * Just to say that the term "hoverfly" is quite well known in the UK as far as I know (our fauna is pretty similar to that found in Germany), and would generally be used for any "mimicking fly" of this sort. I would have called the insect in the photograph "a hoverfly" and am a bit surprised that it isn't. Alansplodge (talk) 09:55, 26 August 2016 (UTC)

Dark clouds
How thick must a rain cloud or thunderhead be in order to completely block sunlight and reduce the ambient illumination from normal daytime levels to nautical twilight levels? (Assume that the sun is 45 degrees above the horizon.) 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 23:21, 23 August 2016 (UTC)
 * Define "thick"? Do you mean the droplet density inside the cloud, or the vertical dimensions of it?  They both would be factors in the ability to block sunlight, and they both could be defined as "thickness".  Indeed, the sunlight blocking ability of clouds is likely due to a number of factors, and isolating any one is likely difficult.  -- Jayron 32 01:30, 24 August 2016 (UTC)
 * The vertical dimensions, given a typical droplet density for these two cloud types. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 03:02, 24 August 2016 (UTC)
 * This document discusses the concept in general terms (search for the word "clouds") and references another NASA document called a "Clouds Fact Sheet" that may be promising. -- Jayron 32 10:40, 24 August 2016 (UTC)