What's this? In mango leaves

Few otherwise previously healthy Mano plants are showing these on leaves what are these?
Is it harmful?
What’s the remedy?
Also best time and how to prune mango plants guidance please
I don’t know how to post images from Android no image upload option seen :slightly_frowning_face:

I would have thought Mango leaf gall midge, but these seem more like pupae of some other moth type insect…


Thanks for the answer, but when I cut open these they seem like plant origin
Will upload cut photo