Elm Sack Gall Aphid

Inside each Elm Sack Gall is the nymph of an aphid, Tetraneura ulmi.

Species introduction

At a glance
Latin name: 
Tetraneura ulmi
Family: 
Aphids
Family Latin name: 
APHIDIDAE
Category: 
Insects other

Species description

Species description

The Elm Sack Gall is a protuberance that grows on the surface of leaves of the English Elm. Inside the gall is the nymph of an aphid, Tetraneura ulmi. When female nymph aphids start feeding on the upper side of a leaf, the leaf reacts by forming a pimple on the upper side. These pimples expand as the nymph feeds and produce offspring. The galls are abandoned in summer, but the insect's life cycle will return it to fresh leaves the following spring.

Species photographs

Larger photograph(s) (click to magnify)
Inside each Elm Sack Gall is the nymph of an aphid, Tetraneura ulmi.
Inside each Elm Sack Gall is the nymph of an aphid, Tetraneura ulmi.

Details

Species family information

Aphids form a very large insect family of sap-suckers. They are generally considered to be a pest although in their abundance they provide nourishment for countless larger insects and birds. They are soft-bodied, pear-shaped insects. Aphids are usually green, but can be red, brown and even white.

Gall mites (and aphids) are too small to be seen by the naked eye - and to be photographed without specialist high magnification equipment. They are therefore exceptions to the rest of the species listings on this website - along with gall wasps - in that their existence in the Cemetery is established not by direct sight but by the evidence of their activity, the nail galls and leaf galls that their activity causes.

Category information

Insects evolved in the Ordovician from a crustacean ancestral lineage as terrestrial invertebrates with six legs (the Hexapoda). This was the time when terrestrial plants first appeared. In the Devonian some insects developed wings and flight, the first animals to do so. An early flying group was the Odonata from the Carboniferous, the damselflies and dragonflies, which have densely-veined wings and long, ten-segmented bodies. They are day-flying carnivores, with an aquatic larval stage, so are commonly seen flying near water. The carnivorous larvae are called nymphs. Odonata species are short-lived, damselflies surviving for 2-4 weeks, dragonflies for up to 2 months.

Some insect groups in the Cretaceous co-evolved with the flowering plants, and they have had a close association ever since. These groups are the Hymenoptera (bees, wasps, and ants), the Lepidoptera (butterflies and moths), the Diptera (flies), and the Coleoptera (beetles). The diversity of beetles is astonishing. Of all the known animal species on the planet, one in five is a beetle!