About Idaea trigeminata (Haworth, 1809)
Idaea trigeminata, commonly known as the treble brown spot, is a moth species belonging to the family Geometridae. This species is found in Europe. Adults have a wingspan of 23 to 25 mm. Idaea trigeminata is similar in appearance to Idaea dimidiata, but it is generally rather larger and somewhat paler. The front edge of its forewings is marked with blackish or dark purplish grey, and a band of the same colour appears on the outer marginal area. The inner edge of this band is formed by the second line, and the outer edge is wavy, interrupted above the middle, and sometimes interrupted below the middle as well. The caterpillar of this species is rough and rather flattened, and tapers towards the head. It is dusky brown in colour. Its markings include interrupted black lines and V-shaped blackish marks on the back. According to Buckler, this caterpillar can be distinguished from caterpillars of its closest related species by a rather long, dingy ochreous bristle that grows from each of its raised dots. These bristles are the same thickness throughout their length, and curve forwards on all body segments up to the ninth, and curve backwards on the remaining three segments.
