Roseslugs are the immature stages of primitive wasps called sawflies. Roseslugs look more like caterpillars than slugs. They are not slimy and do not have rasping mouthparts like true slugs. Roseslugs differ from caterpillars in that their abdominal legs do not have hooklike crochets to cling on to foliage or twigs. There are several species of sawflies that have been reared from roses in North America. Of these three species appear to cause the most damage: 1) The bristly roseslug, Cladius difformis (Panzer), 2) The roseslug, Endelomyia aethiops Fabricius, and 3) The curled roseslug, Allantus cinctus Linnaeus. The bristly roseslug is found in Europe, Siberia, and in North America in Nova Scotia, Quebec, Atlantic Coast to British Columbia and down into southern California, It does not appear to occur in warm climates. This roseslug is pale green in color and is covered with many hairlike bristles all over the body. A full grown larva measures up to 16 mm (5/8 inch). The females are about 5/8 inch long and are shiny black with yellowish-orange markings on the body. The males are much smaller, about 3/8 inch long. The young larva begins feeding as a skeletonizer on the underside of the leaves and as it matures it chews large holes on the leaves. There are as many as six generations each year. The European roseslug is found from California north to British Columbia and east to Quebec and the Atlantic Coast. It is also found in Europe. The adult sawflies are shiny back with a few yellow makings on the body. They measure about 3/8 inch in length. Females deposit their eggs singly in pockets along the margins of the leaves with their sawlike ovipositor. The larvae skeletonize the upper surface of the leaves. A full grown larva measures up to 13 mm (=1/2 inch). This species appears to have only one generation per year I think Bt would get rid of them or some Sevin the first is organic

Thanks Kimmsr, but nope - that's not it. The ones I have are metallic/shiny, like Japanese beetles, and they are also about the same length as they are wide - these are more "sandy" colored and long. I'll have to dig out my camera and see if I can get a good pic of this thing. (Who knew there were so many kinds of beetles?)

I had a similar issue with holes being munched in the leaves of my potted basil and pineapple sage. After coming home late one night I found a lot of insects with massive pincers on their bottoms swarming on these two plants (but none of the other plants, which include mints, oregano, the usual sage, a chili and various other things). I haven't yet worked out how to deter them (as I do not want to use nasty chemicals on my babies), so I bring the pots inside for the night. Any suggestions?

Daniel, yes bacteria breaks down the gunk in a Skippy filter. They need to be pretty big to work properly I think (that's the disadvantage!) I think what happens is, due to their size and design they are able to form a kind of complete ecosystem in themselves, and once they achieve balance, the accumulated muck is broken down at a rate that matches the "fresh" incoming muck. Cleaning them destroys their natural balance. The broken-down gunk becomes nutrients, which feeds more algae so ideally you put something fast-growing in the top of the filter or pond return, to use up the nutrients before they get back to the pond (A veggie filter in other words). Yes, I think you're right about not letting too much sediment settle, I just think its possible to go too far with the flow rates. As with most things, I think you need a balance - high flow rate might "work" better but also mean you need a bigger or more efficient filter (and/or more cleaning!), and a low flow rate might not clear up your water properly...