Watch out for aliens!
Italy has some new inhabitants, but that is no cause for celebration: the list of alien species is long. Two important “aliens” are the harlequin ladybird and the blue crab. Let’s get to know them better…
Originating from central and eastern Asia, the name of the harlequin ladybird (Harmonia axyridis) derives from the variable colour of its wing cases or elytra, which may be yellow or orange with black spots or black with red spots.
Europeans committed the serious error of introducing this species as a means of biological control. Since then, this greedy, aggressive and rapidly reproducing ladybird has prevailed over its “cousins” – seven-spot ladybirds (Coccinella septempunctata) – decimating them to an alarming extent. Entomologists call the phenomenon that may in a very short time lead to the extinction of our ladybird the “war of the ladybirds”.
Another alien species, but which lives in the sea, is the Blue Crab (Callinectes sapidus Rathbun), a species originating from the Atlantic Ocean that arrived in Italy in the ballast water of merchant ships and oil tankers. It is a much sought-after species in the USA due to its tasty meat, but in Italy it raises various concerns: it is a very invasive species that is able to actively prey on fish, molluscs and other crustaceans; it damages fishing equipment when captured and is difficult to eradicate. Its size may be as much as twenty by ten centimetres and it has found a favourable habitat in Italy with ideal chemical and physical conditions, abundant nutrients and mild water temperature.
The presence of species like the harlequin ladybird and the blue crab, defined as alien because they have a habitat different from the one where they were originally found, is increasing at an alarming rate. Italy has been invaded by more than 3000 species. This growing pressure is threatening the biodiversity already challenged by climate changes, pollution and, in general, human disturbance. What can be done to fight these “aliens”? Each of us can and must collaborate by adopting more responsible behaviour and contributing to preventing the introduction of new species and/or curbing the spread of those already present.