| Photo Information |
Copyright: Luis Vargas (Chiza)
![Silver Star Critiquer/Gold Note Writer [C: 34 W: 0 N: 197]](http://i1.treknature.com/misc/s-n-g.gif) (964) |
| Genre: Animals |
| Medium: Color |
| Date Taken: 2009-08-23 |
| Categories: Insects |
| Exposure: f/4.5, 1/80 seconds |
| More Photo Info: [view] |
| Photo Version: Original Version |
| Date Submitted: 2009-08-30 10:58 |
| Viewed: 424 |
| Points: 20 |
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| [Note Guidelines] Photographer's Note [Spanish] |
Cracker butterflies
Calico butterflies
Scientific classification
Kingdom:Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
(unranked): Rhopalocera
Superfamily:Papilionoidea
Family: Nymphalidae
Subfamily:Biblidinae
Tribe: Biblidini
Subtribe:Ageroniina
Genus: Hamadryas
Hübner, 1806
Diversity
About 20 species
Type species
Papilio amphinome
Linnaeus, 1767
Synonyms
Ageronia Hübner, 1819
Amphichlora Felder, 1861
Apatura Illiger, 1807 (non Fabricius, 1807: suppressed)
Peridromia Lacordaire, 1833
Peridromia Boisduval, 1836 (non Lacordaire, 1833: preoccupied)
Philocala Billberg, 1820
Cracker butterflies are a neotropical group of medium-sized brush-footed butterfly species of the genus Hamadryas. They acquired their common name due to the unusual way that males produce a "cracking" sound as part of their territorial displays. The most comprehensive work about their ecology and behavior is that of Monge-Najera et al. (1998) [1].
Underwing pattern of Hamadryas epinome museum specimen
Nearly all species in the genus are fairly cryptic in their dorsal coloration, and they spend most of the day perching on trees, boulders, and other such surfaces against which they are camouflaged. Because of this coloration, these butterflies are also colloquially known as calico butterflies. The speckled species of Hamadryas are often hard to distinguish, and most often these butterflies have to be examined as set specimens. There are no recent revisions, but a general account was published by D.W. Jenkins[2].
Males perch on trees and use them as courting territories, as shown by experiments. They prefer tree bark that matches wing coloration, while presence of food, position of trees along flight routes, tree size, bark texture, and lichen cover are not associated with the frequency of perching on the trees[3].
Each species has a height range when perching but they perch hicher when night approaches.The northern side of trees is less used and cardinal side distribution is independent of time of day. Perches exposed to direct sunlight are less used in hot days. All species perch with the head downwards. Perching males frequently fly towards other butterflies[4].
Each male perches on 1-4 trees daily, without difference between seasons, and each tree used has a minimum daily mean of 1.5 perching butterflies. Most interactions occur from 13:00 through 15:00 hours and are more frequent in the rainy season. At night males share perches[5].
At least seven locations have been proposed for the sonic mechanism of Hamadryas butterflies. Non-destructive experimental methods and scanning electron microscopy suggest that both sexes emit sound and the sound apparatus, located in the forewing, is percussive, not stridulatory. At the end of the upward wingstroke, the wings are clapped and modified r-veins meet at a speed of approximately 1420 mm/s, producing the characteristic clicks. Wingbeat frequency of free-flying individuals is 20-29 Hz. Clicks last a mean of 1.38 ms with mean intervals of 43.74 ms and the component frequencies concentrate around 2.4 kHz, matching Hamadryas hearing capacity and being appropriate for the acoustic conditions of habitat[6].
The swollen Sc vein is present exclusively in Hamadryas; has a serpentine structure inside and probably acts as resonance box. Growth of the sound apparatus may be checked by its effect on flight capacity, physiological costs and ecological reasons. However, this explanation of the sound mechanism has been challenged on the basis of anecdotic observation. All Hamadryas have a membrane, shaped as an elongated cupola, in the costal cell, that acts as ear. A second and smaller ear has four chambers and may detect predatory bats when the insects are perching at night[7].
In the field, Hamadryas emit audible clicks when approached by potential predators, to defend territories from other Hamadryas and in at least one species also during courtship. Severe wing damage, common in wild Hamadryas, almost never affects the section with the sound mechanism. More than 50 species of lepidopterans (11 families) emit sound audible to humans. In general, lepidopteran sound is used basically as a warning to predators and for intraspecific communication[8].
Research has shown that cracker butterflies can also detect the sounds made by other butterflies, which would be a form of social communication[9]. The organ of hearing is believed by some to be Vogel's organ, located at the base of the forewing subcostal and cubital veins[10]. However, they may actually have a larger hearing organ for lower sound wave frequencies [11]. |
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