Arsenura armida

Arsenura armida

The Giant Silk Moth is a moth of the Saturniidae family. It is also known as the Giant Silk Moth. It is found mainly in South and Central America, from Mexico to Bolivia, and Ecuador to south-eastern Brazil.

It is the only known neotropical arsenurine to exhibit a combination of strong aposematism, gregariousness, and trail-following behavior in its larval stage. The larvae are brightly colored, with bright black and yellow bands, which signal their unpleasant taste to birds. The larvae are also fatally poisonous to some species of birds. During the day, the larvae rest in large conspicuous masses on the trunks of trees, and descend at night to feed. When returning at dawn, they follow a silk-less pheromone trail to their original central place location. This social behavior is remarkable for the larvae; other members of the genus live more solitary lives.

The larvae feed on ''Guazuma ulmifolia'', ''Rollinia membranacea'' and ''Bombacopsis quinatum''.

After the larva's 4th instar, it will descend from the larval mass, excavate a small chamber in the soil and pupate. Then, shortly after the rainy season in June, the pupa will eclose. The adult form of the species are large brown moths which possess a wingspan of 100–120 mm. The adults will mate the same night they emerge, and afterwards the females will lay their eggs in large batches on the underside tree leaves.

To the indigenous people of the Zongolica area of Veracruz, the larvae are also a form of sustenance; they are gathered and consumed after being cooked.
A group of Arenura armida caterpillars Punta Laguna, Quintana Roo, Mexico. Jul 8, 2017. Arsenura armida,Geotagged,Mexico,Summer

Appearance

The young larvae exhibit aposematism through their bright yellow and black-ringed bodies and red heads.
The later instars are darker and “duskier” than early instars. They possess a dark brown head, a soma covered with fine short setae, and black tentacle-like protuberances on the dorsum of the thoracic segments. The intersegmental membrane is colored with thin orange-yellow rings.

The adults are large brown moths that like to rest with spread wings. They are predominantly dull-colored, though some may display complex patterns. The adult wingspan is 100–120 mm.
Giant Silk Moth (Arsenura armida) Punta Laguna, Quintana Roo, Mexico. Jun 14, 2017 Arsenura armida,Geotagged,Mexico,Spring

Naming

''Arsenura armida'' is also known as the Giant Silk Moth. It belongs to the subfamily Arsenurinae, consisting of approximately 57 species of Neotropical saturniids found from tropical Mexico to northern Argentina.

Distribution

The Giant Silk Moth occurs mainly in Central and Southern America, from tropical Mexico to southeastern Brazil. They can be found on ''Guazuma ulmifolia'', ''Rollinia membranacea'', and ''Bombacopsis quinatum'' plants. They are also found in Costa Rica in all wildland ecosystems from dry forest to very wet rain-forest.

Behavior

Giant Silk Moth caterpillars are noted for their gregariousness in all phases of larval development. A peculiar phenomenon is the shift in different forms of social behavior from early to late instars.

In early instars, the larvae aggregate at all times in different patches and engage in nomadic foraging. As they age, these moths display a shift to a central foraging location so that larvae feed solitarily at night but, when done feeding, ascend to the canopy at roughly the same time to rest diurnally.

Different hypotheses have been made to try and explain this shift in behavior. In general, caterpillar feeding behavior is shaped by the joint effects of phylogenetic history, larval nutritional ecology, size or apparency, and defensive ecology. Such behavior shifts can be found in other species. For instance, the larvae of many swallowtails begin as cryptic mimics of bird droppings but then switch to aposematism or aggressive mimicry in later instars.

Predation and/or parasitism is hypothesized to have played a role in the grouping behavior and aposematism of the Giant Silk Moth. It is known that the late instar larvae are lethally poisonous to predators such as trogon nestlings, among others, when swallowed. The bright colorings, augmented by the large number of caterpillars in a larval mass, are a visible deterrent to any would-be predators.

Habitat

The Giant Silk Moth occurs mainly in Central and Southern America, from tropical Mexico to southeastern Brazil. They can be found on ''Guazuma ulmifolia'', ''Rollinia membranacea'', and ''Bombacopsis quinatum'' plants. They are also found in Costa Rica in all wildland ecosystems from dry forest to very wet rain-forest.

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Taxonomy
KingdomAnimalia
DivisionArthropoda
ClassInsecta
OrderLepidoptera
FamilySaturniidae
GenusArsenura
SpeciesA. armida
Photographed in
Mexico