Could you help identify a (very) large black flying insect. It had 2 wings only (actually may have been tapered/pointed, not rounded) and when at rest formed a crucifix and looked like a black flower. I guess it was 3-4cm across and the same anterir-posterior. It was emptying a wisteria, in full bloom, of its nectar. It was not bothered by our failed attempts to photograph it. When it flew off it was 'bumbling' along and flew over our house. It came back the next day for more juice from the wisteria. We see very little else feeding from this plant. It was big!

sorry but without a picture it is almost impossible to help with identification.