AppearanceThe average length is 16-20 millimeters, with males being smaller than females. They are able to fly, making a buzzing noise when airborne. Western conifer seed bugs are somewhat similar in appearance to the wheel bug and other Reduviidae . These, being Cimicomorpha, are not very closely related to leaf-footed bugs as Heteroptera go; though both have a proboscis, but only the assassin bugs bite even if unprovoked, and ''L. occidentalis'' like its closest relatives can be most easily recognized by the expanded hindleg tibiae and by the alternating light and dark bands which run along the outer wing edges on the flaring sides of the abdomen. Their primary defense is to spray a bitter, offending smell, though sometimes they can smell pleasantly of apples, bananas or pine sap; however, if handled roughly they will stab with their proboscis, though they are hardly able to cause injury to humans as it is adapted only to suck plant sap and not, as in the assassin bugs, to inject poison.
HabitatIn its native range, the Western Conifer Seed Bug feeds on the sap of developing conifer cones throughout its life, and its sap-sucking causes the developing seeds to wither and misdevelop. It is therefore considered a minor tree pest in North America, but becoming sometimes more harmful e.g. in conifer plantations. However, it is not monophagous and even adaptable enough to feed on angiosperms if it has to, though it seems to prefer resiniferous plants that are rich in terpenes. As these are produced by plants to deter herbivores, it might be that in evolving its ability to overcome these defenses, ''L. occidentalis'' actually became somewhat dependent on such compounds.
Its host plants in the native range include conifers like the Lodgepole Pine , the White Spruce , and the Coast and Rocky Mountain Douglas-firs . Outside the native range, it is also found on species like the Eastern White Pine and Red Pine in eastern North America and Europe, and the Mountain Pine , European Black Pine , Scots Pine and Pistachio in Europe.
The eggs are laid in small groups on the needles or leaf stems of its host plants, and hatch in spring. The nymphs go through 5 instar stages before moulting into adults. In the USA, the species is univoltine, but in southern Europe, it completes two generations a year, and in tropical Mexico even three. In the northern parts of its range, these bugs start to move about widely by September or so to seek crevices for overwintering; they may become a nuisance in areas with extensive conifer woods, as they will sometimes enter houses in considerable numbers. They have the potential to become structural pests, as it has been found that they will sometimes pierce PEX tubing with their mouthparts, resulting in leakage.
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