Amyna axis

Amyna axis
Amyna axis larvae
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Lepidoptera
Family:	Noctuidae
Genus:	Amyna
Species:	A. axis
Binomial name
Amyna axis (Guenée, 1852)
Synonyms
Perigea octo Guenée, 1852 Amyna octo (Guenée, 1852) Perigea axis Guenée, 1852 Poaphila stricta Walker, 1858 Calaena flavigutta Walker, 1858 Celaena perfundens Walker, 1858 Ilattia cephusalis Walker, [1859] Amyna colon Guenée, 1862 Perigea vexabilis Wallengren, 1863 Miana inornata Walker, 1865 Celaena obstructa Walker, 1862 Perigea leucospila Walker, 1865 Erastria stigmatula Snellen, 1872 Stridova albigutta Walker, 1869 Erastria bavia Felder & Rogenhofer, 1874 Segetia orbica Morrison, 1875 Amyna undulifera Butler, 1875 Chytoryza tecta Grote, 1876 Botys monotretalis Mabille, 1879 Perigea supplex Swinhoe, 1885 Berresa rufa Bethune-Baker, 1906

The Eight-Spot (Amyna axis) is a moth of the Noctuidae family.

Distribution

It is found in the tropics and subtropics worldwide, and occurs in Africa, India, Indonesia. Australia and the Cook Islands.^[1]

The moth migrates north each year in late summer and fall. It is common in southern North America, from Florida to Arizona. It is a regular migrant to the mid-eastern states, and rarely as far as Wisconsin, Ontario and Quebec.

Adults are on wing from August to October.

Life cycle

Food plants

The larvae feed on Amaranthus, Croton, Celosia, Digera, Helianthus, Chenopodium, Spinacia, Ipomoea, Ricinus, Arachis, Crotalaria, Medicago, Phaseolus, Hibiscus, Cardiospermum, Solanum, Corchorus and Parasponia species. ^[2]

It is an irregular minor pest worldwide of mung beans (Vigna radiata), black-eyed peas (Vigna unguiclata), lucerne (Medicago sativa) and soy beans (Glycine max). Their prevalence may be under-reported due to the resemblance of the caterpillar with those of Chrysoieixis species.^[1]

Early stages

The larva are thin-bodied have faint white stripes and two pairs of ventral pro-legs.^[1] At low densities caterpillars are pale green. Among caterpillars at high densities there are higher frequencies of melanistic phenotypes. The degree of blackening varied widely, ranging from individuals with simple subdorsal-lateral patches to those that were mostly black.^[2]

Larvae perch on the undersides of leaves and along stems and petioles. At rest, the abdominal segments are often looped upward. When alarmed the larva essentially jumps from the host and continues to wreathe and wriggle wildly. Prepupal larvae take on a pinkish cast. Pupation occurs in a silken cocoon below (usually) or at the soil surface. Sand and/or plant debris are interwoven into the cocoon wall.^[2]

Adult

The adult moth is chocolate brown above and has a wingspan of 20-25 mm. The forewings have faint greyish-white lines and an obscure figure-of-eight mark on it. The hindwings are lighter with fainter markings. The male can be differentiated by the presence of a small semi-transparent patch on each wing.^[1]

Gallery

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  Last instar larva:1. Chaetotaxy. SD2 on abdomen represented only by its pinaculum (forward of spiracle); 2. Head, frontal; 3. Labrum, frontal; 4. Mandibles, mesal surfaces

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  Last instar larva: 5. Head, frontal; 6. Head, lateral, with prothoracic gland (adenosma) indicated; 7. Crochets, with subapical tooth indicated

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  Larvae caudal segments

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  Prepupa

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  Pupa and cocoon

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  Pupa ventral (left), lateral (right)

References

1. ^ ^{a b c d} Bailey, Peter (2007). Pests of Field Crops and Pastures: Identification and Control. CSIRO Publishing. pp. 528. ISBN 9780643067585. http://books.google.co.in/books?id=N10sAEHunWEC. Retrieved 29 April 2010. 
2. ^ ^{a b c} Wagner, DL; Binns S (2010). Larva and pupa of Amyna axis (Guenée, 1852) and affirmation of its taxonomic placement in Bagisarinae (Lepidoptera, Noctuidae). ZooKeys. p. 4. ISSN 13132970. http://pensoftonline.net/zookeys/index.php/journal/article/view/435/389. Retrieved 29 April 2010. 

External links

• Images
• Bug Guide, listed as Amyna octo