I don't have any experience with western tigers or their host plants, Murray, but after willows, my books list poplars, aspens, several alders and sycamores, cottonwood and ash.
Do you have a Forest Farm catalog? You could undoubtedly find small trees/bushes in their catalog from those families. I wish I could give you some first-hand information.
Sherry

Hi Misssherry, I do have the Forest Farm catalog but it doesn't specify which alders and there are so many and the same with the other suggested host species so I am hoping to find specific trees or shrubs that are small. I saw Sweet Bay listed and some prunus species but there are so many of those too. But thanks for the suggestions. I have decided to keep the willows going until I find a solution. Our weather still has not warmed up and our rainy season is still going on as well so the lack of butterflies may be in part due to that problem. I will keep on trying though. Murray