Which type of termite has two dark veins at the front border of their wings?

The correct answer identifies a characteristic feature of subterranean termites. Subterranean termites, which include the Formosan subterranean termites, typically have wings with two distinctive dark veins along the front border. This is a key identifying trait that can help differentiate them from other types of termites.

In contrast, the other types mentioned do not share this specific wing vein pattern. Drywood termites have a different wing structure that lacks these dark veins, making them distinct from subterranean species. West Indian powderpost termites are also not recognized for the same wing vein configuration. Understanding these specific anatomical details is critical for proper identification and management of termite species, particularly in pest control and prevention efforts.