On a silver maple. Horntails are an intriguing group of insects. This large female (about 1.5 inches long) of the species lays her eggs into the bark of trees using that strong ovipositor. When a female lays an egg, she also injects a mix of mucous (nutritional), and what is called a "fungal innoculum" which prepares the wood for fungal growth on which the larvae feed. However, the larvae are unfortunately the prey of the huge Megarhyssa wasps (next set of photos). The female of this latter sp., determines whether Horntail larvae are present and if so, she inserts her gigantic ovipositor straight down and lays her eggs on the poor Horntail larvae, thus ensuring that her offspring will have something to eat!

These Horntails are harmless despite their size and colouration which makes people believe they must be very dangerous. That "stinger" you might see if you notice these wasps,is either the ovipositor or the 'horn' which gives them their common name.