Simply by relying on an old brain with old knowledge rather than checking new text books with new knowledge. But why, you ask, was the old brain fooled? It had forgotten that diffinis is an incredibley variable species as is thysbe. If we go back to Holland (1903) we see that he treated what is now diffinis as 2 separate species: diffinis and thetis. Furthermore, he considered diffinis to be trimorphic: f. diffinis, f. tenuis, f. axillaris. Add thetis to this and you get a quadrimorphic species. Holland (1903) considered thysbe to be dimorphic: f.thysbe and f.cimbiciformis. Jumping ahead to Forbes (1948); 4 forms of diffinis were recognized: f. diffinis, f. tenuis, f. axillaria, f. aethra. Forbes also considered thysbe to have 4 forms: f. thysbe, f. fuscicaudis, f. floridensis, f. cimbiciformis. Hodges’ Check List (1983) gives 14 synonyms for diffinis, and 9 synonyms for thysbe; all once considered separate species! D’Abrera (1986) “Sphingidae Mundi� (based on the collection in the British Museum) shows photos of 3 subspecies of diffinis: diffinis, tenuis, ariadne and 1 form: f. rubens. D’Abrera shows 2 forms of thysbe: f. thysbe, f. fuscicaudis.

Can you see why I was confused?

So what’s my problem? Among others, the northern form of diffinis, and the one I get here in NB, is f. aethra and it looks similar to Holland’s photo of thetis on Plate II. The northern form of thysbe is cimbiciformis. Now the NB specimens of thysbe (cimbiciformis) look very much like Photo#18039 which I believe is diffinis f. axillaris. Northern diffinis don’t look like this southern form of diffinis. Thus southern axillaris diffinis look like northern cimbiciformis thysbe.

Lesson to be learned: check locality of specimen; and northern leppers should not pass judgement on southern leps.

It will be interesting to see how Jim Tuttle treats the species in this genus in his forthcoming book on NA Sphingidae.

Anthony W. Thomas

Bob,

Thanks for that detailed explanation. Here's another view of the same specimen:

Does that show the clear discal cell?

..... that is a perfect illustration of the cell. In the other two species the cell margins appear to be thickened or partly filled in. This is a case where multiple photos of the same individual can be an aid to identification.

Matthew,

You're right. I was looking at pictures of Snowberry clearwings, and made a mistake. It looks very much like a Snowberry clearwing.

I dont get it. Are these things rare or something? I have collected at least 10 of these in my neibors yard easilly. Along with the same ammount of tiger swallowtails.

you may have been correct the 1st time. I've photographed both diffinis and thysbe in similar poses and this one doesn't look anything like diffinis I get in NB. Of course, this is only a guess and I can't supply any references. I'm probably wrong and you should wait and see what others may think about the ID. It may not even be thysbe. Thysbe and gracilis are very difficult to separate when in flight. It's a very nice photo.

Anthony W. Thomas