Nice to meet you all!

Hello everyone, my name is Vincent. I'm a 25 year old from San Diego, California, but I'm currently working in rural Japan as an English teacher. I've been wanting to get a pet, but my apartment here is not the biggest, so my girlfriend convinced me into getting a mantis.

I recently purchased a few mantids (two female Hestiasula major and one "common flower mantis", which I don't know the sex or scientific name of). The sellers both told me that they hatched around 1 month ago, but the Hestiasula majors are way bigger than the flower mantis. Does anyone know why this might be? Is this due just due to them being different species, or do you think the sellers didn't tell the truth about their age? Please let me know if you have any answers. Thank you and nice to meet you all!

welcome!
that flower mantis is a Creobroter, the exact species we can't tell until it's an adult

The mantis are different species. The small one will only be about an inch or so more when adult, whereas the other will be will be bigger hence the size difference. Welcome

Welcome. There is no escape. : )