A Visual Guide to Indian Lygaeinae Identification

work in progress; any attempt to build a key is hard, as no current exhaustive list of the species present in India is available; but still, I felt this might be of some use here, providing help for Milkweed Bugs (subfam. Lygaeinae) identification in India, perhaps helping to build such a reference list that will allow the eventual creation of a key. Only the most common species are featured here, I will complete with time.

Spilostethus

Two species occuring in India.
Spilostethus nymph are much easyly recognised by being the only genus in India bearing red patches on wing buds (the only other possibility being Haemobaphus from Southern Africa), though S. hospes can have entirely dark wing buds, that never happens in S. pandurus.

Spilostethus pandurus


Kanchan Verma, Raipur, CT, 2021

An almost cosmopolitan species, the only one in the genus that eventually reached America. Pretty variable, with at least three valid subspecies, the most well-known being S. pandurus elegans from Southern Africa, alongside with the rarer and more located S. pandurus asiaticus from Madagascar and S. pandurus tetricus from Canarias. There is a questionable synonymy between the typical nominal form(s ?) S. pandurus pandurus and S. pandurus militaris, from Europe, Northern Africa and Near East, that have likely never been formaly synonymised, and are more or less confused - and therefore rarely used.

The form occuring in India, though not formally described, is a Asian form differing slighly from the nominal one. Mostly with an Indomalayan distribution, it occurs westward from Persian Gulf and the East coast of Arabian Peninsula (with the central, desertic areas from the central Arabia appearing as a natural boundary, as the scarce populations from the western coast appear to be closer to that of Europe and Northen Africa, or transitional form), Pakistan (with a boundary and some transitional forms somewhere in Afghanistan), to Sulawesi Eastward, and is likely widely distributed in South to Himalaya in Pakistan, India, Thailand, Cambodge, and Vietnam (with but very few available data from Bengladesh and Myanmar, but unlikely missing from those country, so likely abundant there to), and extends southward on the Oceanic domains to Indonesia, Malaysia and the Sunda Islands.

S. pandurus is overall greater, up to 12, or even 13 mm ; pronotum pattern can bears two palish yellow-greenish spots between the dark fascia, sometimes missing, but never present in hospes. Scutellum is entirely black from base to apex. The membrane is dark, from black to greasy grey, with a white central macula, and a smaller basal spot, sometimes missing, especially on pale and/or withered specimens.
Asian forms differs from the nominal one by being overall darker, with greyish shading, the dark black patterns tending to be outlined by a grey marking that overlaps the light red coloured parts.
The transversal corial bars present on typical forms tend to be reduced, often not reaching inner corial margin and even outer corial margin, and looking closer to a more or less rounded spot.

S. pandurus feeds on a wide variety of plants, including many Asteraceae; as for many other "Milkweed Bugs", it appreciate Apocynaceae, that it is likely immune to toxins and can thrive on. In India often found (though alongside other species) on Calotropis procera.

Spilostethus hospes - "Darth Maul Bug"


Vivek Babu Girija, Kancheepuram, 2022

S. hospes is nicknamed "Darth Maul Bug" in Australia, a name that doesn't appear to be much in use in India, but tends to extand, due to the Internet community, and is due to its strikingly contrasted red and black pattern.

It is true that, in India, with S. pandurus on average more greyish, it will be most often easily recognised by its contrasting colours. (Oddly enough, this is not quite true in Australia where the name comes from, and where other Spilostethus species similarly colored such as S. pacificus or S. decoratus can happen...).

Tending to be slighly smaller (though no known precise measures from India are known) and more gracile, it seems close to the African (in expansion, and now extending up to Southern Europe) S. furcula, and is easily recognised by its scutellum always red at the apex (sometimes this very reduced in some Austro-Malayan populations, but always true for Indian ones), that, alongside with the similarly red clavi, builds an easily-recognisable " _/ " red pattern on the back.
Membrane is usually dark, but rarely really black, most often of a deep dark brown or grey, sometimes lighter (especially in some old/withered specimens), and always unspotted, that allows it to be easily distinguished from the nearby S. pandurus.
The corial pattern includes a rounded black macula on each coria, never reaching the corial margin (unlike the sibbling S. furcula, that bears a transversal dark bar extending from external margin most often to the inner one, but is not present in India).

Like S. pandurus, S. hospes also appreciates Apocynaceae, and both can often be met together on Calotropis procera. Another common host species in Asia is the Asteraceae Emilia sonchifolia.

Aspilocoryphus mendicus


Anubhav Agarwal , Kancheepuram, TN, 2019

Genus close to Graptostethus. Body densely covered with hairs, pronotum mostly dark greyished patterned, with two black spots on it. Red colour very reduced in this species. Can be distinguished from Graptostethus by the darker head, and the white spot on the membrane, that is connected with inner corial margin.

Posted by fabienpiednoir fabienpiednoir, November 24, 2022 17:36

Comments

Great work, thanks! But there is a small technical issue – the link to Aspilocoryphus mendicus image is incorrect - it's not a direct link (https://www.inaturalist.org/photos/56890078?size=original). Correct link: https://inaturalist-open-data.s3.amazonaws.com/photos/56890078/original.jpg

Posted by kgrebennikov about 17 hours ago (Flag)

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