Some species are easily identifyable, such as the weird Gasteruption jaculator. With most insects the tail is attached to the thorax at the bottom. With this species it is fixed to the top and then hold in an upright position. And if that isn't bizarre enough the ovipositor sticks out in a straight line and is white-dotted. Gasteruption jaculator is small, but because of all the protuberances it looks like something much bigger! It belongs to a family called Gasteruptionidae. The behavior is that of Parasitic Wasps.
Gasteruption jaculator measures 14 to 18 mm, but because of their long ovipositors females appear to be much bigger. In our garden this species is especially interested in the nests of the Red Mason Bee. The Mason Bees make their nest in deep holes in our old garden gate. The females of Gasteruption jaculator inspect these holes regularly and if the nest is good, the long ovipositor is put into the hole and nest and a single egg is laid on top of the or near the egg of the bee. After hatching the larva of the wasp first eats the egg or the larva of the host and then eats the food the bee has collected for her off spring. The wasps larva overwinters and pupates in spring.
Gasteruption jaculator has only one breed a year, but they are seen for a long period of time: from May to September. That is not because they are extremely long lived, but because they use a number of wasp and bee species as host. Because these species do not all develop at the same time, neither do the parasites and so fresh adults appear all summer.
The females from this family may be told apart easily by looking at the length of the ovipositor, even though there are some "doppelgängers". The males are very difficult to tell apart. They lack the ovipositor which comes in so handy in excluding the first species. Gasteruption jaculator probably is the most common species in England. It certainly is a species often seen, for frequently it is in the vicinity of (man made) bee hotels and it loves to visit flowers in gardens during day time.