Biology

T. troglodytes is relatively large for an aphid - adult females are 3 to 4mm long.

Colonies consist almost entirely of wingless females, which give birth to live young without being mated (parthenogenesis).

Winged females are sometimes produced which can fly away to found new colonies on other plants. But often the ants clip off their wings so they cannot fly, forcing them to stay, produce daughters and add to the size of the existing colony.

The body, antennae and legs of T. troglodytes are densely covered in fine hairs, which prevent it getting wet or dirty.

Trama troglodytes showing rostrum, stylets, antennae, fore leg and eye

Like other insects, most adult aphids have compound eyes, but as T. troglodytes lives underground these are greatly reduced. The T. troglodytes eye is a group of 3 minute lenses on each side of the head, called triommatidia.

T. troglodytes has long hind legs. The hind tarsi are particularly long when compared with other aphids. They may be used to stroke ants and stimulate them to collect the abundant honeydew produced by the aphids, which would otherwise become mouldy and spoil the colony.

Reproduction

Trama troglodytes, leg showing middle leg, hind leg with femur, tibia and tarsus

Aphids reproduce without sex (parthenogenesis).

A series of all-female generations are produced through spring and summer. This allows them to exploit the growth of their host plants to the full, and build up very large colonies.

Most aphids also have an annual sexual generation, usually in the autumn, when males are produced, together with a special type of female that mates and lays overwintering eggs.

This type of reproductive cycle is called cyclical parthenogenesis.

For many years scientists thought that T. troglodytes and its relatives had given up sex completely, as no males had ever been found.

Trama troglodytes DNA

Trama troglodytes chromosomes have large and variable amounts of non-coding, repetitive DNA - stained black in the photograph.

In addition, scientists at the Museum found out that Trama has unusual chromosomes with large and variable amounts of non-coding, repetitive DNA (stained black in the photograph).

This might be expected to interfere with the chromosome pairing and recombination (meiosis) which occur during sperm and sexual egg production.

Then, molecular analysis of Trama DNA provided evidence that genetic recombination does sometimes occur.

This evidence has led scientists at the Museum to search through numerous colonies of Trama troglodytes for males of the species.

After many hours work they found one very small male, wingless and completely blind, but with its sex organs intact and functional.

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