since this insects easts mostly flowers check your yard to see what kind of flowers you got growing. then check online to see if they have toxins. the only concern might be the fact the insect has a pretty hard shell which wont digest really well. but i wouldnt worry too much. the insect itself doesnt carry any toxins. good luck!
the Japanese beetle on its own is not toxic, but read the thread here: https://www.chameleonforums.com/beetle-invasion-4626/
in particular the response from Kinyonga. The eat an enormous selection of plants but if you have roses and/or fruit trees (pear, apple - all in the rose family) these are often their preferred.
However, they do have very spiny legs but it doesn't sound that the cham had any problem getting it down. Keep an eye on his poop (to be sure he does not get impacted) and don't be surprised if you see bits of leg or wings that he simply could not digest and just passed through.
2 1/2"?? How old is this little guy? Chams preferably are not sold any younger than 3 months. Just curious, you said cage - screen? If he is that small you may want to keep in a tank to help maintain humidity. Here's an article that you might find helpful. babycare Also, can you put sealant or a grommet around this area that you think it got in? If a firefly gets in and he eats it then yes, you have a serious problem. But for now he should be OK
Dean Pulcini said...."They know what they can eat like a harmless beetle and also the size of the insects"...I have to disagree with you on that..chameleons have been known to ingest fire flies, lady bugs and certain grasshoppers and caterpillars that are toxic to them.
Chameleons may recognize insects from their own wild habitat as being toxic (I'm not sure if that would even be completely true)....but not what we might find in the field or chose to feed them in captivity.
A bit further afield...would a chameleon avoid a wild caught hornworm and then eat a captive raised one? How would the chameleon know if the insect ate a toxic plant before it ate the insect?