new to keeping predatory beetles - what to feed Calosoma scrutator

[Jacob Ma]

You guys are right! It may or may not have been noticed, but if you look at the beetles' pretarsi (front legs, at their feet), the segments in the males are much more squarish than the females triangular/trapezoidal segments. So it looks like you guys all get credit!

In case you didn't know, the pretarsi on males helps with gripping onto the female during mating.

 

[Hisserdude]

You guys are right! It may or may not have been noticed, but if you look at the beetles' pretarsi (front legs, at their feet), the segments in the males are much more squarish than the females triangular/trapezoidal segments. So it looks like you guys all get credit!

In case you didn't know, the pretarsi on males helps with gripping onto the female during mating.

Interesting, thanks for sharing! Looks like there is a reliable way to sex Calosoma after all! Can all ground beetles be sexed this way?

 

[ErinM31]

Good to know

You guys are right! It may or may not have been noticed, but if you look at the beetles' pretarsi (front legs, at their feet), the segments in the males are much more squarish than the females triangular/trapezoidal segments. So it looks like you guys all get credit!

In case you didn't know, the pretarsi on males helps with gripping onto the female during mating.

Good to know -- thank you! It is similar in some toad species; the males have protrusions on their front digits to help grip the female.

 

[MWAInverts]

In a lot of beetle species the pretarsi segments on males will be highly modified for grasping. I do believe almost 100% of male aquatic beetles have them as well.

 

[Jacob Ma]

They are different in a lot of shelled species, as this adaptation is even evident in tortoises. However, the pretarsi segments vary in appearance, like for aquatic beetles there is a large suction cup instead of dilated segments to grip to smooth shells in flowing water. For most ground beetles, this adaptation is featured on them, but as I said it varies in appearance so it may or may not be difficult to tell the sex of a male or female.

 

[BobBarley]

Interesting, thanks for sharing! Looks like there is a reliable way to sex Calosoma after all! Can all ground beetles be sexed this way?

To me, it the difference looks evident in these to pictures of P. depressus

Male with more roundish segments on their front legs: http://bugguide.net/node/view/371153/bgpage
Female with more triangular segments on their front legs: http://bugguide.net/node/view/520032/bgpage


EDIT: Also, in P. californicus:
Male: http://bugguide.net/node/view/903980/bgpage
Female: http://bugguide.net/node/view/935302/bgpage

 

[Hisserdude]

To me, it the difference looks evident in these to pictures of P. depressus

Male with more roundish segments on their front legs: http://bugguide.net/node/view/371153/bgpage
Female with more triangular segments on their front legs: http://bugguide.net/node/view/520032/bgpage


EDIT: Also, in P. californicus:
Male: http://bugguide.net/node/view/903980/bgpage
Female: http://bugguide.net/node/view/935302/bgpage

Very interesting, thanks for sharing! That picture of the P.californicus male also says: One of the noticeable external features of male P. californicus, shared with male P. punctulatus, is a dense brush of golden setae on the apical third of the hind tibiae.

 

[ErinM31]

Very interesting, thanks for sharing! That picture of the P.californicus male also says: One of the noticeable external features of male P. californicus, shared with male P. punctulatus, is a dense brush of golden setae on the apical third of the hind tibiae.

Yeah, it seems it won't be difficult to tell the males and females apart after all. Also, finding a male will help determine whether I have P. californicus or P. depressus (although I suppose it's entirely possible that both could live around here). Right now, my money is on P. depressus.

 

[BobBarley]

Alright, well if you ever try to sex your live Pasimachus, they do not stay still. I ended up taking a video and looking through the frames for the one millisecond that my P. viridans stayed still. Well, relatively still at least... Looking male!

 

[Hisserdude]

Alright, well if you ever try to sex your live Pasimachus, they do not stay still. I ended up taking a video and looking through the frames for the one millisecond that my P. viridans stayed still. View attachment 209913 Well, relatively still at least... Looking male!

Yeah, that's a problem that happens with a lot of bugs, it's hard to take a picture of something when it's running or flying all over the place, especially if you are going for a small portion of the body.
I agree, looks male!

 

[ErinM31]

Alright, well if you ever try to sex your live Pasimachus, they do not stay still. I ended up taking a video and looking through the frames for the one millisecond that my P. viridans stayed still. View attachment 209913 Well, relatively still at least... Looking male!

Nice! You've a good camera to get such focus in close-up. My iPhone doesn't do well on things that small. I need a camera with a macro lens!

 

[BobBarley]

Nice! You've a good camera to get such focus in close-up. My iPhone doesn't do well on things that small. I need a camera with a macro lens!

Lol I actually use an iPad mini! I bought a macro lens for $10 on Amazon.

 

[ErinM31]

Lol I actually use an iPad mini! I bought a macro lens for $10 on Amazon.

Oh wow! I thought I was going to have to wait until I could afford an expensive camera -- I had no idea they sold inexpensive macro lens attachments for iPhones -- awesome!