InsectNet forum

A bred pair of the spring form. Thanks to Adam Cotton for doing such a good job with these.

Dave,

I am glad you like them. You did a superb spreading job on them.

Interestingly I could not breed any summer form specimens here. All pupae went into diapause regardless of the time of year, presumably because the day length here is less than 14 hours (11-13 hours depending on season) triggering diapause. This must be the reason that P. xuthus does not reach tropical zones. It gets as far south as northernmost Vietnam (Hagiang only). This species also has no subspecies, despite its wide range.

Adam.

A splending species.
I still remember seeing it flying in Tokyo when I was 10 years old.

Does xuthus still fly on Hawaii? I seem to recall that it had established there several decades ago.

jh

jhyatt wrote: Sat Mar 08, 2025 3:52 pm Does xuthus still fly on Hawaii? I seem to recall that it had established there several decades ago.

jh

It did as of about seven years ago. I can’t imagine it disappeared.

Strangely I was told by the person who brought me some that in Hawaii it only ever produces summer form specimens. I find this hard to believe, but it would be interesting to know whether that is true or not.

Adam.

I saw a number of them on Kauai in January of 2023.

Xuthus is everywhere in Hawaii. Summer form was on the wing when I visited some years ago (both times during the winter months in the north). It was easy to find eggs and larvae on citrus.

I checked my records. I found them on Oahu and Kaui.

Eurytides, those photos are great, and the first one is spectacular. It made me really appreciate the beauty of the larva.

Thanks Chuck. Eggs were super common, one just had to look. I remember one day during my second trip there, we stopped by a roadside stand where someone was selling juice. They had an orchard in back and I asked if I could have a look. Found several eggs in under 5 minutes. First trip there, we went to the botanical garden and there was a citrus in the parking lot. Again, found several eggs and young larvae, and old eggshells. The photo of the egg I posted is from that parking lot. The larva is really cool and tropical looking. I think the pattern is beautiful. There is a framed picture of the larva in my home office.

More:

eurytides wrote: Sun Mar 09, 2025 8:08 pm Summer form was on the wing when I visited some years ago (both times during the winter months in the north)

This suggests that the information I was told that there is only summer form all year round could be true. I wonder why P. xuthus apparently doesn't go into diapause in Hawaii, and why this species cannot similarly survive at similar latitudes in Asia. The southernmost point in its distribution (Dong Van, Hagiang, Vietnam ~23°13'N) is further north, and the smaller spring form is present there. Where I live in Chiang Mai the latitude is 18°43.6'N and Hawaii is only about 1 degree further north but all generations went into diapause here. I put pupae in the fridge for about a month or more to break diapause, and it didn't make any difference what time of year the adults emerged to breed on, all generations went into diapause.

Adam.

eurytides wrote: Mon Mar 10, 2025 1:37 pm Eggs were super common, one just had to look. I remember one day during my second trip there, we stopped by a roadside stand where someone was selling juice. They had an orchard in back and I asked if I could have a look. Found several eggs in under 5 minutes.

Note that Eurytides has eagle’s eye.
I wouldn’t find anything there most likely

The irony is that my eye sight is terrible and I have had glasses since I was a kid. I always tell people the key to finding eggs is knowledge, practice, and patience.

Here’s a picture from the orchid. 2 eggs on a single branch. We had to drive back to our hotel so I didn’t stay long. I could have easily found 100 eggs just along the side of the road.