Mon 2014-04-21 
A pair of Bibio sp, probably Bibio lanigerus (Diptera: Bibionidae), mating. Female at the top with the small eyes, male at the bottom with the large eyes.
Photo taken in Whiteknights Park, Reading, UK, on 2014-04-19.
Sun 2014-04-20 
A pair of Anthomyiid flies of the Anthomyia procellaris species group (Diptera: Anthomyiidae) mating.
Photo taken in Whiteknights Park, Reading, UK, on 2014-04-19.
Sat 2014-04-19 
A leaf of holly (Ilex aquifolium) with black spots. This above image shows the upper surface of the leaf, the image below shows the lower surface:
Under my stereo microscope most of the spots on the lower surface had a small hole at their centre and in a couple of these holes contained what looked like an insect egg:
Note added 2014-05-04: The black spots might be the fungus Coniothyrium ilicis. As not all of the spots have holes in them it is probable that the egg-laying insect deliberately selected the fungal patches in which to lay its eggs, presumably because the leaf surface was weaker there.
Specimen taken in Whiteknights Park, Reading, UK, on 2014-04-12.
Fri 2014-04-18 
A female Eristalis petinax (Diptera: Syrphidae). Just a few seconds before it had dropped the yellow 'egg' from the rear end of its abdomen; dropped not laid: it seemed only by luck that the 'egg' stayed on the leaf.
Photo taken in Whiteknights Park, Reading, UK, on 2014-04-12.
Thu 2014-04-17 
A female Elgiva cucularia (Diptera: Sciomyzidae).
Specimen caught in the field below Chazey Wood, near Caversham, UK, on 2014-04-13.
