The na­ture of things

Small tor­toise­shell but­ter­fly

Country Life Every Week - - Town & Country Notebook - Edited

THE case of the dis­ap­pear­ing tor­toise­shell: it’s a co­nun­drum wor­thy of Holmes or Poirot. For­merly abun­dant and seen ev­ery­where, Aglais ur­ticae has been miss­ing, in re­cent years, from many of its for­merly fa­mil­iar haunts. Var­i­ous grounds for its re­treat have been sug­gested, from too-tidy gar­den­ers to the mod­ern de­fault rea­son for all ills—cli­mate change. An­other thought is that the flour­ish­ing of the par­a­sitic fly Stur­mia bella in re­cent years has had a knock-on ef­fect on but­ter­fly num­bers. It’s the stuff of hor­ror sto­ries: the fly lays its eggs close to the but­ter­fly’s feed­ing cater­pil­lars; the lat­ter eat the fly eggs whole, where­upon the swal­lowed eggs hatch out grubs, which slowly eat the de­vel­op­ing but­ter­fly lar­vae from the in­side.

Male and fe­male small tor­ties look sim­i­lar. The up­per sur­face, when wings are open, re­veals a back­ground of deep tan­ger­ine, against which smudges and bars of black and yel­low are sym­met­ri­cally ar­ranged, beaded with lit­tle dots of blue along the wing mar­gins. The folded wings, how­ever, are the acme of smudgy-brown dis­cre­tion, cau­tiously im­i­tat­ing un­ap­petis­ing, rot­ting leaves to fend off po­ten­tial preda­tors.

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