Introduction
The Ithomiini comprises of 376 known species, although it is likely that at least another 30 will be discovered in the near future. All are confined to the neotropical region. Ithomiines are unpalatable to birds, and are consequently mimicked in appearance by many other species.
These include other unpalatable species (Müllerian mimics), not only from the Ithomiinae but also from several other butterfly families. There are also a large number of edible species (Batesian mimics) which have evolved similar patterns. Birds have the ability to memorise butterfly patterns and so learn to avoid eating noxious species, but are also fooled into ignoring similarly marked edible species.
Ithomiines are characterised by having small eyes, slender abdomens and long drooping antennae that lack distinct clubs. Males have a plume of long androconial scales or ‘hair pencils’ on the costa of their hindwings. These are hidden from view when the butterflies are at rest, but are displayed when the wings are held open during courtship. Other Ithomiine characteristics include a very slow and deep wing beat, and a preference for inhabiting the darkest recesses of the forest understorey.
There are basically 2 types of Ithomiine. The first type are the black and orange-banded ‘tigers’, many of which are mimicked by other species due to their unpalatability to birds. The second type are the ‘glasswings’, recognised by their transparent or translucent wings, prominent veins, and orange wing margins. Many genera contain examples of both of these types, and in some cases an individual species may produce adults of both forms according to location.
Most novices find the Ithomiini very difficult to identify. Using only the patterns to identify species is very unreliable because there are so many similar species. Also many species produce a variety of different colour forms according to locality and season. The best approach therefore is to use the hindwing venation and other anatomical features to identify the genus, and to then look at the wing patterns to short-list the likely species.
Tithorea are large butterflies. They often fly in sunny glades where they can easily be confused with Heliconius species such as ismenius, numata or hecale. The easiest way to distinguish Tithorea from their mimics is to examine the antennae and legs.
Tithorea antennae are very gradually tapered, and drooping. In Pieridae they are parallel along the stalk, with a strongly clubbed tip, while in Papilionidae the tip is clubbed and recurved. Ithomiines, Heliconiines and Nymphalines have only 2 pairs of functioning legs. In the Ithomiines these are long, giving the impression of a butterfly on stilts. Papilionidae and Pieridae have 3 pairs of functioning legs.
Tithorea harmonia is one of the commonest and most widespread of the toxic ‘tiger’ species, being found from Mexico to the southern Amazon. There are 26 named subspecies.
Habitats
This species is found in sub-tropical deciduous forest as well as in evergreen rainforest habitats. It occurs at altitudes between 0-1300m.
Lifecycle
The larvae feed on Prestonia acutifolia (Apocynaceae). These foodplants contain toxins that are ingested by the larvae and passed on to the adult butterflies, rendering them highly distasteful to birds. Other Ithomiines are also noxious to birds, but obtain the toxic pyrrolizidine alkaloids found in the adult butterflies are sequestered by the adults from nectar or plant exudates rather than being sequestered in the larval stage.
I do not have any descriptions of the early stages of harmonia, but they are likely to be similar to those of the closely related species T. tarricina. The larva of the latter is pale green with dark bands around the segments, and has two long filaments arising from the first thoracic segment. The pupa of tarricina is silvery and resembles a large water droplet.
Adult behaviour
Tithorea harmonia is usually encountered singly, but at the Alto Rio Madre de Dios in Peru I once found over 20 flying together, possibly the result of a spontaneous mass emergence.
In sunny weather the adults tend to be secretive, flying in light gaps in the understorey. In cloudy conditions however, or at the approach of dusk, they emerge into more open areas along the edges of streams or wide forest tracks. There they can be seen fluttering amongst herbage, or settled on low foliage, slowly fanning their wings.
Males are commonly attracted to bird droppings, from which they sequester pyrrolizidine alkaloids. These chemicals serve multiple purposes – they increase the toxicity of the butterfly rendering it unpalatable to birds, they are essential in the production of pheromones, and they are transferred to the female during copulation thereby increasing her longevity and fertility. Males often visit the same bird dropping on 3 or 4 successive days.
Both sexes visit flowers including Psychotria, Hamelia and Chomelia. They share with Heliconiines the habit of spending long periods nectaring at individual blooms, and habitually return to the same flower over a period of days.
In dry weather the adults roost openly on foliage in the understorey, but during rainy spells they hide amongst the rootlets of palms. At the end of the dry season they and other Ithomiines tend to gather at the last remaining sources of moisture within the forest, such as dry river beds, marshy areas or muddy pools.