or could (in this context) be used to indicate its habitat is marshlands??

This is a tough one, and according to google and my colleagues there are several possibilities, Chrysolina (Chrysomela) banksi being most likely, but couldn't get a 100% hit. You may have to get around this one and "recast" the whole sentence to read "Other leaf beetles of the genus Chrysolina (americana, sanguinolenta, banksi, etc.) are also present/native to our Garrigues. When Linnaeus designed this system, he had the best intentions, but with insects in particular, genera, species, even whole families and orders have since been reclassified many times, but the French names derived from them don't change. Some of these critters are still in the genus Chrysomela, others (like the ones in your text) have since been reclassified in the genus Chrysolina, and not all of them may have accepted English language common names, esp. ones that may not be found in countries where English is spoken.

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Note added at 1 hr (2010-01-02 17:27:14 GMT)
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I once heard that when He created the world, God must have had a special love for insects and of the insects, the beetles in particular. There are more different kinds (species) of insects than all other kinds of living things, plants and animals, put together, and more different kinds of beetles than other insects. The Chrysomelidae (leaf beetles) are a huge family, a favorite topic for taxonomists who love to literally "split hairs" on insects, hence the mess of different names and reclassifications, and why you often see Chrysolina (Chrysomela) banksi, or whatever, indicating that both names are still used in the literature. This family contains numerous species that are well-known agricultural pests, and even they have been reclassified!