Sawflies and wood wasps

Hymenoptera (bees, ants, wasps (solitary and social) & saw flies). The Hymenoptera is an order in the phylum uniramia, arthropoda or insecta according to which book you read.

Uniramia

--Centipedes

--Hexapoda 1 (insects)

--Hexapoda 2 (insects)

--Hexapoda 3 (insects)

--Identification to order level

--Insect orders

----Lepidoptera (butterflies, moths)

----Ephemeroptera (mayflies)

----Hemiptera (bugs, cicadas)

----Hymenoptera (bees, ants, wasps & saw flies)

------Bumblebees

----Coleoptera (beetles)

----Dictyoptera (mantids, cockroaches)

----Diptera (true flies)

----Neuroptera (lacewings, ant lions)

----Orthoptera (crickets, locusts)

----Thysanura (bristletails, silver fish)

----Strepsiptera (stylops)

----Thysanoptera (thrips)

----Odonata (dragonflies, damselflies)

----Trichoptera (caddis flies)

----Siphonaptera (fleas)

----Isoptera (termites)

----Phasmida (stick & leaf insects)

----Dermaptera (earwigs)

----Anoplura/siphunculata (sucking lice)

----Mallophaga (biting lice, bird lice)

----Psocoptera (book, bark, dust lice)

----Mecoptera (scorpion flies)

----Collembola (springtail)

----Embioptera (web spinners)

----Plecoptera (stone flies)

----Diplura (bristletails)

----Protura

----Zoraptera

Symphyta or saw flies

Symphyta are a sub-order of the order Hymenoptera. The main difference between saw flies and the other Hymenoptera is that saw fly adults do not have a "wasp waist", see left. Also none of them are social. There are around 10 000 species of saw fly in he world, and around 500 British species, although there are no native saw flies in New Zealand. The saw fly fossil record stretches back 180

million years to specimens found in what is now Russia and Australia. They are considered to be the most "primitive" of the Hymenoptera.

Adult saw flies

The adults have simple mouthparts and feed mainly on pollen, although some adults are partly carnivorous. They got the name saw fly because most of the females have an ovipostior that has visible saw-like teeth (see below). The female uses it to cut slits in plant stems and

leaves, then she lays her eggs in the slit. Saw flies do not have a sting.

Saw fly larva

The larvae feed on plants, and look very much like caterpillars. However moth and butterfly caterpillars have 5 or fewer pairs of prolegs, whereas saw flies have six pairs or more (see above). The larva often feed communally on the edges of leaves. When disturbed

they hold on to the leaf with their front legs and wave their rear ends in the air. Pupation takes place in a cocoon. Above is a drawing of a saw fly saw used in cutting into plants. Most saw flies have such structures, but some species have a more conventional ovipositor that sticks out of the rear and looks more like a drill than a saw. These are often given the name of horntails or wood wasps.

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Wood wasps (Sircicae)

Siricidae family. Adult length is from 20 - 40 mm long. They are usually brown or black marked with yellow. Both male and females have a tail, but only the females have an ovipositor - usually longer than the tail (see right). Fossilised wood wasps have been found dating back 160 million years in what is now Kazakstan.

On the right and below left is the wood wasp or horntail Urocerus gigas. It is not a wasp at all as it can be clearly seen below that it has no "wasp waist" that all bees, wasps and ants have.

Also although this female - and it is usually just the female wood wasps we see - looks fearsome, she is quite harmless. The very

Urocercus gigas, wood wasp, adult female

worst she can do is fly into you. This is a typical example of a harmless insect gaining protection from predators by mimicking a harmful one. The long, dark brown thing sticking out of her rear end is not a sting, but her ovipositor. With it she drills vertically 5 - 10 mm into wood - usually a diseased, unhealthy or dead conifer - and injects 4 - 8 eggs.

Males are rarely seen as they tend to fly around the tops of trees only when the sun shines looking for a mate.

Urocerus gigas are found in forests that have sunny clearings. They are fast and noisy fliers, and fly only when it is sunny, usually from May onwards. Female adult length is 24 - 44 mm, male adult length is 12 - 32 mm. The antennae are many-segmented.

The eggs hatch in around 4 weeks and the larva spends its time eating the wood-destrying fungi that its mother thoughtfully injected along with the egg. At the base of the ovipositor there is a pair of glands that contain the fruiting bodies of the fungus, and some of these are injected with each egg. The larval stage lasts for 2 1/2 - 3 years, and the tunnel they make can be 30 cm long. Before pupation they tunnel to around 1 cm from the tree surface, then pupate, so that when the adult emerges it has only 1 cm of wood to gnaw through to reach the outside. The wood wasp larva is preyed on by a Ichneumonid wasp, Rhyssa sp. This wasp has an ovipositor almost 4 cm long, and searches for prey by exploring the wood surface with her long antennae until she can pick up the scent of a wood wasp larva. It will take her around 20 minutes to drill through the 3 cm or so of wood to reach the wood wasp larva where she deposits a single egg.

Urocerus gigas, wood wasp female, horntail female, diagram showing parts of the body

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