The Western Conifer Seed Bug is a ‘true bug’ that belongs to the:

Order: Hemiptera, from the Ancient Greek word for ‘half-winged’.

Sub-order: Heteroptera, from the Greek for ‘different wings’, as they have forewings with both membranous and hardened areas.

Family: Coreidae, leaf-footed bugs, from the leaflike shapes on their hind legs).

The adults are large, spectacular squash bugs with an average length of 15-20 mm and a width of 5-7 mm, with females larger than males.

Description

Their squarish ‘shoulders’ and long, four-segmented antennae are easily seen, and when they spread their wings, they show off their yellow and black abdomen. Harder to see are their piercing-sucking mouthparts and paired odoriferous glands.

Despite spraying a nasty-smelling alarm pheromone as a defence mechanism, they are not stink bugs.

Originally native to the USA, it is thought they were introduced to Europe through timber exported to Italy in 1999, with the first English records in 2007. A large influx of Western Conifer Seed Bugs was recorded on the south coast of England in the autumn of 2008, indicating natural immigration from continental Europe, and they have spread quickly since then.

Their range is still expanding, and they have been recorded across the county.

They feed on conifers and are now well-established. They are attracted to light and will enter buildings searching for hibernation sites in the autumn.

They produce one generation yearly and have a simple (incomplete or hemimetabolous) metamorphosis with no pupal stage before adulthood.

Adults emerge from overwintering hibernation in mid-to-late spring.

Females lay up to 80 light brown barrel-shaped eggs that they glue to pine needles in chains during May and early June. The eggs gradually darken to a reddish brown, and the nymphs hatch after 10 to 14 days.

Young nymphs are orange but become darker, larger and more developed with each of their five moults. In late August, they finally reach their adult stage.

First instar nymphs feed on the needles and tender tissue of cone scales, while the later-stage instars and adults feed on developing seeds, early flowers and cones. They stick their needle-like proboscis into the conifer seed, inject a digestive liquid to break down the seed’s energy stores and then drink it. 

Bugs that look similar

The Box Bug and Denticulate Leatherbug both look superficially similar. However, they are much smaller, about half the size of a Western Conifer Seed Bug, and neither have enlarged tibiae or the white zig-zag.