I went on holiday and found an alien!

Every now and again, me, my wife, and some friends go for a short holiday on the Isle of Wight (it's not far away and there's a house we can borrow for free!). Last time, we found a fossil crocodile - this time a small alien appeared inside on one of the windowsills...

Dorsal view of the insect which is 18mm long 'nose to tail'.

As it happens, it was already dead when found, but well preserved, just missing a front leg. This made it particularly obliging and easy to photograph. It's also a distinctive species in the UK and is an adult Western Conifer Seed Bug Leptoglossus occidentalis (note the white zigzag mark across the middle of the wings), a true bug (Hemiptera) in the family Coreidae (squashbugs). A native of North America, it was first found in Britain in 2007 when a single specimen appeared in a college in Dorset, southern England. Since then, there have been numerous sightings all over the country, though most commonly along the south coast, suggesting migration across the English Channel following its introduction to continental Europe (northern Italy) in 1999, after which it spread widely and rapidly. Nymphs have also been found in Britain, indicating at least one breeding population and adults have been known to enter buildings to hibernate (possibly the source of this specimen); adults fly well, making a buzzing sound - being relatively large (but harmless to humans), this means they are often easy to detect if they enter houses.

As the common name suggests, it is associated with conifers and feeds on the cones and seeds of over 40 species, particularly trees in the family Pinaceae. In North America, it can be a serious economic pest of conifer nurseries (e.g. causing a large proportion of conelets to abort) but in Europe it is generally found in gardens and parks so such impacts have not been seen, and future effects are uncertain - nor does it attack timber. So, let's have a look at our little alien in more detail.

Close-up of the head and pronotum (the 'head cone' is about 3mm long).

Here it is clear that the reddish pronotum has a detailed pattern of yellow blotches containing tiny black spots, while the head is dark with a central red stripe and other smaller red marks. Also, the antennae which appear smooth at a distance are actually densely covered in short bristles.

Dorsal view of the wings.

Here, the distinctive zigzag markings on the forewings are clearly visible, as is the venation of the membranous hindwings, the covering of short bristles, and the black-and-white markings on the edge of the abdomen ('connexivium').

Ventral view of the head and thorax showing the pointed mouthparts (rostrum).

The long rostrum is clearly visible here and is jointed with the section lying underneath the head having fine transverse lines (striations). The rostrum is formed from mouthparts modified to peirce and feed on plant tissues and is attached to the front of the head (in other suborders of Hemiptera, the attachment might be further back). You can also see where the front right leg was attached - now missing, there is a green blob where the point of attachment sealed over.

A close-up of the hind leg.

Lastly, the hind leg provides another distinctive feature (along with the reddish colour and pale zigzags) allowing this species to be easily identified. The inner edge of the hind femur is armed with sharp teeth, but the key feature is the flattened leaf-like shape of the hind tibia which can be seen clearly here along with the tiny black dots puncturing it. Again, although the legs look smooth at a distance, they actually have dense tufts of hairs.


So, although this species has only been in Britain for a few years, it appears to be spreading rapidly and as it is so distinctive, you have a fair chance of seeing one (possibly in your house), especially in the south. For more info on it, I recommend the excellent British Bugs page which includes links to a life stages chart and a more detailed factsheet (which provided some of the info here) as well as the recording scheme for sightings of this species in the UK.