Sexing tiny Scarlets, et. al.

[mickiem]

I've had 6 scarlet millipedes for a month or so and had never sexed them. I'm getting 12 more and wanted to make sure I have a colony with mostly females. Any time I see one on the surface, I try to sex it - they are HARD to sex! But I outsmarted them. I took a glass cube with a smooth glass bottom and placed each millipede in it. I took a close up photo from underneath and blew it up on my pc screen. How do you sex those little ones??

 

[ErinM31]

I've had 6 scarlet millipedes for a month or so and had never sexed them. I'm getting 12 more and wanted to make sure I have a colony with mostly females. Any time I see one on the surface, I try to sex it - they are HARD to sex! But I outsmarted them. I took a glass cube with a smooth glass bottom and placed each millipede in it. I took a close up photo from underneath and blew it up on my pc screen. How do you sex those little ones??

That sounds clever! The males will be missing a pair of legs on the seventh or eighth segment where they are replaced by the gonopods. Also, you can see gonopores at the base of the legs on the third segment of the males. I'd be happy to take a look if you'd like to post the photos here.

 

[mickiem]

That sounds clever! The males will be missing a pair of legs on the seventh or eighth segment where they are replaced by the gonopods. Also, you can see gonopores at the base of the legs on the third segment of the males. I'd be happy to take a look if you'd like to post the photos here.

Thanks, Erin! Do the Scarlet males have a hood? they are so small it is hard to see the gonopods even when I enlarge the photo (not great quality). I've deleted the photos; but I'll remember to post next time. It's easier to see the gap in the legs from the side than to see the gonopods/ pores. Maybe no one messes with sexing these little ones? I'm a little OCD. I like more females in the colony.

 

[ErinM31]

Thanks, Erin! Do the Scarlet males have a hood? they are so small it is hard to see the gonopods even when I enlarge the photo (not great quality). I've deleted the photos; but I'll remember to post next time. It's easier to see the gap in the legs from the side than to see the gonopods/ pores. Maybe no one messes with sexing these little ones? I'm a little OCD. I like more females in the colony.

By "hood", are you referring to the first segment behind the head? https://en.wikipedia.org/wiki/Millipede#/media/File:Millipede_anterior_anatomy.png
How prominent or "hood-like" this segment appears depends on the type of millipede; there is no difference between genders.

The gonopods may be more difficult to see when the millipedes are young or they may be more difficult to see on Spirobolid millipedes. I find them difficult to see on any of my male Spirobolids but I can usually see the gap in the legs and the gonopores (at least on mature adults). Flat millipedes (Polydesmids) are easier to sex since their legs are further apart and their gonopods seem to be more prominent.

I agree; it is ideal to have a few males with several females. A one-to-one ratio is not bad, but I would avoid having more males than females as even millipede males can fight in their way and stress everyone. Of course this too varies among species.

 

[mickiem]

By "hood", are you referring to the first segment behind the head? https://en.wikipedia.org/wiki/Millipede#/media/File:Millipede_anterior_anatomy.png
How prominent or "hood-like" this segment appears depends on the type of millipede; there is no difference between genders.

I'm confused. I thought some (like Ivories) have a hood (enlarged segment) between the head and gonopods that indicated a male.

I am very new at all of this but I'm in deep. I read reference to this in Orin McMonigle's books. In, Millipedes in Captivity, he lists 'hood' in the glossary and eludes to a sex differential.

 

[ErinM31]

I'm confused. I thought some (like Ivories) have a hood (enlarged segment) between the head and gonopods that indicated a male.

I am very new at all of this but I'm in deep. I read reference to this in Orin McMonigle's books. In, Millipedes in Captivity, he lists 'hood' in the glossary and eludes to a sex differential.

You are right; males of some species such as Chicobolus spinigerus (Ivories) have this enlarged segment but most do not. You can see it in my photo below of a pair of Ivories below, their heads toward the bottom of the photo and the male on the right:

 

[mickiem]

You are right; males of some species such as Chicobolus spinigerus (Ivories) have this enlarged segment but most do not. You can see it in my photo below of a pair of Ivories below, their heads toward the bottom of the photo and the male on the right:
View attachment 217210

Ok, so I'm not crazy. I thought it was more common than not, though. I have Ivories, so I see it there. It seems like they get the hood early, too. I have some that are barely 2 inches and sporting a hood. Wish they were all that easy!

 

[ErinM31]

Ok, so I'm not crazy. I thought it was more common than not, though. I have Ivories, so I see it there. It seems like they get the hood early, too. I have some that are barely 2 inches and sporting a hood. Wish they were all that easy!

No, you aren't; I had forgotten that Orin used the term "hood" for that. As for how common it is, I do not know whether any male millipedes outside the order Spirobolida display this characteristic. Certainly "flat-millipedes" (Polydesmida) do not. Within the order Spirobolida, I know that C. spinigerus and N. americanus do while N. gordanus and Floridobolus do not and if Tylobolus males have an enlarged segment, I have not perceived it. I have no idea about Spirobolids outside the family Spirobolidae (such as the Scarlet millipede) nor those not found in North America.