x1 is a silkmoth/silkworm [probably Bombyx] of species/breed/type x2
No implication is made about its present life stage; for specific/scientific usage, use bombiksia; for the larval/caterpillar/worm form, use sikykemciftoldi; for the moth/mature/adult form, use sikma'ubortoldi; for the cocoon, use siktodlanka or todbi'olanka. Since many moths have silken cocoons, in order to reference a member specifically of genus Bombyx, use bombiksia.