吐丝 is a separable verb (离合词) meaning 'to spin silk', used specifically for silkworms and other insects that produce silk threads. The verb 吐 ('to spit, to emit') and the noun 丝 ('silk') can split when you add a measure word or duration between them — for example, 吐了三次丝 ('spun silk three times'). You cannot put an object after 吐丝; the silk is already part of the word.