Other of with a/an/the
 

p.173 I have read other of your poems of Insect Life, and marvelled at the way they combined the brilliance and fragility of those winged things [...]

Is an- or the optional before other?

Yes, here there is no need for either.

Excellent answer. Thank you. But do you think an- or the would make the thing clearer? If there's three poems, after reading one, we say another poem; there's two poems, after reading one, we say the other poem.

You can use the alternatives, yes.

In formal writing, "there's" should be "there're" when talking about more than one, since it's the proper contraction for 'there are'.

Excellent answer. Thank you.