Jonah, I take Howley’s argument to be that while restrictionists are always blaming the demand for illegal immigration on people’s desire to shirk lawnmowing duty, which implies that men would have to pick up the slack if restrictionists had their way, in fact the cost of cutting the supply of immigrant labor would fall hardest on women. Moreover, this cost would be borne not only by high-income women but by women in general.

But the evidence Howley adduces in support of these claims is thin.

According to a recent report (pdf) by the Department of Human Development at Cornell University, over sixty percent of children under 5 are in some form of non-parental care on a regular basis. Single mothers are more likely than most to seek informal, unregulated child care arrangements, where stay-at-home mothers charge a fee to watch other people’s children during the day.
Women’s labor force participation is widely acknowledged to be sensitive to the price of child care in the United States, where a thriving private market helps stem the call for universal taxpayer-subsidized preschool and daycare. Child care prices are obviously sensitive to the supply of child care providers.

That “over 60 percent” figure is seriously misleading: A majority of the kids included are getting that regular non-parental care from a relative, presumably often unpaid. (Here’s the study that actually provides the statistics.) Anyway, the argument that we need to cut the pay of some women–those stay-at-home mothers who charge a fee to watch other people’s children, for example–in order to help other women, and that this is somehow good for women generically, seems to me to be pretty weak.

Of course you are correct that reductions in the supply of immigrant labor would have negative consequences for some people (although Howley doesn’t come close to showing that women–of all classes!–would be disproportionately affected negatively).