Uroctonus mordax Breeding Report

In April 2008, I was presented with a female Uroctonus mordax that was caught 14 miles west of Corvallis, Oregon.

The female on April 10:

As time progressed, she was observed to have grown larger, and she was suspected to be gravid. Possible embryos were observed through her membrane between the tergites and sternites. She was checked on in early July and had not yet undergone partuition.

On the afternoon July 13, 2008, the female was found with a brood of first-instar scorplings on her back.

Brood size at this time was estimated at greater than 16 scorplings. Humidity was raised and the female was left undisturbed to avoid stress that may lead to cannibalism.

The scorpions were checked on periodically throughout the next week by holding a flashlight to the side of the enclosure and looking through gaps between the piece of cork they were hiding under and the substrate. As all that was seen was a pile of white scorplings, the cork was not removed.

On the evening of July 23, 2008, a similar check raised suspicions that the young appeared too well-developed to still be first-instar (though they were still very white). The cork was removed for a brief photography opportunity.

These photographs revealed that the young had indeed begun to molt into second-instar. Because they were still so pale, it was assumed that this had happened very recently and they had not yet started to darken (wild observations found dark specimens believed to be second-instar, though it is possible they were third).

Another check on the morning of July 26th showed only slight darkening, but revealed that some of the young had begun to scatter from the mother's back.

The final check occurred on the evening of July 31st, 2008, and revealed that all but three of the young had left the mother (one remained on her "face," one on her pedipalp, and one was hanging on underneath). Looking at the substrate and the cork that the young were hiding on gave a final count of 26 second-instar Uroctonus mordax.

The female was removed at this point to hopefully determine the communal nature of juveniles of this species, and prey (pinhead crickets) was offered at this time. No feeding has yet been observed.

The young were found to fluoresce at this point, so it is assumed that their exoskeletons have finished sclerotization.

Basic timeline:

April 2008: female acquired
July 13: brood discovered
July 23: 2I discovered
July 26: slight darkening of young, scattering started
July 31: young completely scattered, mother removed, prey offered