Does anyone know how the brown hairstreak came to be associated with birch? Its Latin name, betulae, means 'of the birch' and in French it is known as la thècle du bouleau - meaning the birch Thecla.
The reason I ask is that today, every time I passed birch trees (which was a lot - they lined the track most of my walk), I saw male (mostly, but maybe some females) brown hairstreaks zooming in or out. I only managed to catch one sitting still, high in a tree:
I didn't see any blackthorn along the track, though there might have been some in the extensive wild regions off the track. Is it possible they really do take Betula as a foodplant? For those who don't know me, I live in Switzerland and these particular tracks were between 900m and 1000m above sea level.
It would seem it was listed as a LHP in most books up to the 20th century. Humphrys (1859) and Morris (1870) both list it alongside Blackthorn as a foodplant. Why it was ever listed I have no idea but I suspect it may be a case of Chinese whispers from an initial error at some point in the early days of Butterfly enthusiasts. It's interesting that it loses favour in the guides close to when Frohawk did his work on our Butterflies. Having a quick flick through Frohawks tomb, he makes no mention of birch whatsoever.
I think it's extremely unlikely they use it as an alternative given that it's completely unrelated to Blackthorn.
Thanks Buggy. Since posting the question, I've found a couple of recent references to brown hairstreak taking birch. Tristan Lafranchis, in La Vie des Papillons, after noting different larval + pupal stage lengths on different foodplants (93 days for apricot, 98 days for blackthorn and 102 days for plum), observes, 'Malgré son nom français, la chenille de la Thècle du Bouleau n'a été trouvée que très occasionellement sur cet arbre en Allemagne et en Scandinavie' ('Despite its French name, the brown hairstreak caterpillar has only very occasionally been found on this tree [birch], in Germany and in Scandinavia'). Lepido.ch also makes reference to Scandinavia: 'La Thécla du bouleau porte mal son nom car il n’a aucun lien avec le bouleau en Suisse (mais il utilise parfois le bouleau comme plante-hôte en Scandinavie)' = 'The brown hairstreak wears its name badly, as it has no connection with birch in Switzerland (though it sometimes uses birch as foodplant in Scandinavia).' I'll ask them where they got that information from. Interesting that Linnaeus, who named the butterfly betulae, was Swedish.
The hairstreaks yesterday had a choice of birch, aspen, sallow, larch and various bushes to fly around but they definitely went for the birch, and over a wide area. I feel an egg-hunt coming on this winter ...
Curiouser and curiouser, perhaps Birch is used as a master tree in some places too? I've seen them using sycamore in the past. Is the place devoid of Ash trees?
This is all very interesting. Having spent many years studying this species in the central Lincolnshire Limewoods, and having located and mapped the distribution of tens of thousands of overwintering ova over more than 25 years, I could wax lyrical about its preferences for various ages/types/orientations of Blackthorn growth when it comes to ovipositing. However, with just a few exceptions, I have hardly ever found eggs on anything but Blackthorn.
The few exceptions are a number of eggs laid regularly at just one site on some sort of wild, thornless, plum species, and another occasion where, bizarrely, I found a single betulae ovum on Oak.
I should also point out that I have never actively searched for betulae eggs on Birch, even though it is a very common tree species in its Lincolnshire territories.
The only place in continental Europe where I have found betulae eggs is central southern Brittany, in what I considered to be rather unlikely Brown Hairstreak habitat- very sparse Blackthorn, but plenty of Birch thinking about it!
At least one individual (the one I photographed) clearly was using the birch territorially, or as a lek, but most of the others didn't seem to be. I'll keep you posted if I find anything new.
And yes, Fraxinus and birch do indeed go back a long way - right to the very roots of our language in Proto-Indo-European! The ever-helpful Wikipedia gives a good summary:
"The common name birch comes from Old English birce, bierce, from Proto-Germanic *berk-jōn (cf. German Birke, West Frisian bjirk), an adjectival formation from *berkōn (cf. Dutch berk, Low German Bark, Danish birk, Norwegian bjørk), itself from the Proto-Indo-European root *bʰerHǵ- ~ bʰrHǵ-, which also gave Lithuanian béržas, Latvian Bērzs, Russian берёза (berëza), Ukrainian береза (beréza), Albanian bredh 'fir', Ossetian bærz(æ), Sanskrit bhūrja, Polish brzoza, Latin fraxinus 'ash (tree)'. This root is presumably derived from *bʰreh₁ǵ- 'to shine, whiten', in reference to the birch's white bark. The Proto-Germanic rune berkanan is named after the birch." (I changed the spelling of the Sanskrit word, as Wikipedia had it wrong, but I can't vouch for all the other languages!).
