The other night there was a tug of war on the outside of my bathroom window between two house geckos:
The female (above, with eggs clearly developing inside) had a grip on the head and the male had the abdomen in its mouth. The poor 'rope' was a Hippotion, either boerhaviae or rosetta which are very difficult to distinguish without genitalia preparation.
The male won, and was later still on the window with the abdomen in his mouth, and the next day I found the remains of the moth minus its abdomen.
It seems that Sphingid heads must be much more securely attached to the thorax than Papilionids, as geckos usually grab a Papilio by the head breaking it off leaving a headless body on the ground.
I hate geckos ! They always eat moths and butterflies which just came to the light . I remember in Mukdahan a Sphingid came to house light and I had to run to my car to grab the net , upon return all I could see was one fat gecko with my moth in its mouth .