Eye of a hornet, made with magnification 5 and f/13 using a Canon 7D and a Canon MP-E 65mm/f2.8. The size was around 30-35 mm.
The European hornet Vespa crabro, commonly known simply as the "hornet", is the largest European eusocial wasp. The queen measures 25 to 50 mm (1–2 in) long; males and workers are smaller. In males, as in most members of the Aculeata, the antennae have 13 segments, while in females there are only 12; also as in other aculeates, the male abdomen has seven visible segments, while the female has six; females possess an ovipositor modified into a sting which is not barbed (source: Wikipedia).
This species is rather aggressive around food sources such as lilac bushes and will sting without warning. They are also known to be very defensive of their hive, therefore care must be taken when in its proximity. Its sting is quite painful with the pain and swelling known to persist for several days. As with most stinging insects, European hornets will sting in self-defense when grabbed or stepped on.