I believe it is because butternut stems are solid instead of hollow like zucchini.

Butternut and all C moschata varieties are theoretically resistant to SVB, not squash bugs, because of their solid stems.

I have seen a couple of sites that say they are resistant to squash bugs, but I always think the writers must not know that "squash bugs" are a specific insect and not a general term for insect pests of squash plants. Or else they get svb confused with squash bugs.

I've seen butternut vines get killed by SVBs. Holes bored in stems, with the tell-tale frass. It's not easy for them to do it, but they can. It's fine to say that moschata are "resistant" to SVBs, but they are hardly immune.

Yes Sunni i think your right on the writers being confused on squash bugs v. SVB.

I do think that C. moschatas are resistant (but not immute) to squash vine borers, and that they are non-preferred by squash bugs if summer squash (C. pepo) is available. When I do have squash bugs on butternuts (moschatas) the populations are small and nowhere near as intimidating as when they infest zukes and other summer squash. I have never had borers in any moschata, but I have always had more attractive plants available.

I only have this year to base my observations on and they didn't quite line up with what I had read. I have a long row of C. moschata with a couple of C. pepo at the end. The pepos are nominally to be a trap crop for the squash bugs since I had read that they were preferred over the moschatas. The moschatas are an experiment to see how well they stand up to svb. So far both sets of plants have been visited by both types of insect. There were pretty much the same number of adult squash bug found on both varieties on a daily basis, so it didn't seem like they preferred the pepos. The pepos have now collapsed from svb, and I haven't bothered to try to save them having had my annual dose of summer squash. They were always destined to be trashed anyway. The moschata have evidence of svb damage on the stems but are not (yet anyway) collapsing. So moschatas being svb resistant? Check. C. pepo being preferred by squash bugs? Doesn't seem like it this year. Bu tlike I said, it's only one year.

Have only had squash bugs here the last year or two, and they've defiitely preferred the butternut.

What people call squash bugs, I call stink bugs, and are a bigger problem for tomatoes than squash. They actually prefer sucking on tomatoes than sucking on leaves, but they will do either. Unlike SVBs, they don't go after the stem exclusively and try to penetrate it, so the lack of a very hollow stem in moschata is irrelevant to them.

Hmmmm well they have set up shop in the butternut now that the zucchini is gone. I am hunting them daily though so i hope the plants will be fine :)

I have had butternut squash vines hold up after a squash bug hatch much much better than any zuke could ever do. The vine does eventually die, but it really makes a valiant effort to live, and often you can get it to produce mature squash if you search out the growing hatchlings and kill them. A zucchini would never make it that long. So yes, it's resistant.