Invertebrates
Giraffe Weevil
Trachelophorus giraffa · also called giraffe weevil, madagascar giraffe weevil
The giraffe weevil is a small red-and-black beetle from Madagascar with an absurd feature: in the male, the neck is a long, jointed arm two or three times the length of the female’s. He uses it to lever rival males off a branch. She uses her shorter version for something more practical — folding a leaf into a tube as a cradle for a single egg.
Overview
The giraffe weevil is endemic to Madagascar, living in humid forest on a few species of host plant on which its entire life cycle takes place. The body is about 2.5 cm long with bright red wing cases and a glossy black head, thorax, and legs. The extended neck adds considerably to a male’s length.
The neck
The male’s neck is a greatly elongated front section of the thorax and head, working as a lever in wrestling contests with other males. Rivals face off along a stem and try to push and flip each other off the branch; the winner mates with the nearby female. Because neck length decides these fights and signals quality, it is under strong sexual selection, which is why males’ necks are so extreme and females’ are short.
The rolled-leaf nursery
The female cuts and folds a single leaf of the host plant into a tight tube, lays one egg inside, and detaches or abandons the roll. The larva hatches within its own rolled-leaf cradle, feeds on it from the inside, and later emerges to pupate.
A short life
Adults do not bite or sting, fly only weakly, and live just a few weeks, spending that time feeding, fighting, mating, and rolling leaves.
Status
The giraffe weevil has not been assessed. It is locally common on its host plants but depends entirely on Madagascar’s forest, which continues to be cleared.
Giraffe Weevil: common questions
Why does the male giraffe weevil have such a long neck?
It is a weapon and a signal shaped by competition for mates. Male giraffe weevils fight over females and over the best leaves for egg-laying, and the fights are wrestling matches conducted on a narrow stem. A longer neck gives a male more reach and more leverage to push, hook, and tip a rival off the branch, and it also advertises his size and quality to females and to other males before a contest even begins. Females, which use their necks only for the practical job of rolling leaves, have much shorter ones. Over many generations this difference in how the sexes use the neck has produced the extreme length seen in males.
How does the giraffe weevil make its rolled leaf?
The female works a single leaf of the host plant in a set sequence. She first makes cuts across the leaf, often on both sides of the midrib, which causes the leaf to wilt and become pliable. She then folds it over and begins rolling it from the tip toward the base into a tight cylinder, tamping and tucking as she goes with her legs and mouthparts. Somewhere in the process she lays one egg inside the developing roll. The finished tube, a few centimetres long, protects the egg and then the young larva, which feeds on the rolled leaf tissue from the inside before eventually emerging, pupating, and becoming an adult.
Is the giraffe weevil dangerous or a pest?
No. It has no sting, its jaws are not strong enough to hurt a person, and it is a weak flier that is easy to approach. It feeds only on a few specific wild host plants in Madagascan forests, not on crops, so it is not an agricultural pest, and it exists in modest numbers rather than swarms. Its main significance is as a striking example of sexual selection and of Madagascar's unusual wildlife, and it is a favourite subject for wildlife photographers visiting the island's reserves.
When was the giraffe weevil discovered?
It was formally described by the French entomologist Léon Fairmaire in 1889, so it has been known to science for well over a century. What is more recent is its fame. High-quality photographs of the weevil circulating online from the late 2000s onward, showing the male's improbable red-and-black form in close-up, turned a fairly obscure Madagascan beetle into one of the more widely recognised insects in the world, frequently featured in articles about strange or beautiful animals.