The gorse spider mite (GSM), Tetranychus lintearius, is a monophagous herbivore that produces denser communal silk webs than those of the closely related but polyphagous herbivore, the two-spotted spider mite (TSSM), T. urticae. While candidate fibroin proteins, as well as salivary proteins that coat silk fibers, have been reported in TSSM, their conservation and expression in GSM remain unclear. This study aimed to compare silk-associated proteomes between the two species to uncover the molecular basis underlying the contrasting webbing strategies in the context of host adaptation. Silk threads and whole-body samples from both species were analyzed using label-free LC–MS/MS with three biological replicates per condition. Proteins were identified against the TSSM protein database as a reference. Relative abundances were compared between species (GSM vs. TSSM) and between sample types (silk threads vs. whole-body). Functional annotation focused on secretion, protein processing, and energy metabolism pathways. Proteomic analysis revealed clear species-specific differences in silk protein composition. Several fibroin candidates were more abundant in silk threads of TSSM than in those of GSM. However, a glycine-rich secreted protein (GRSP) was highly abundant in GSM silk threads, while its levels in whole bodies were similar between the two species. The GRSP in GSM contains an N-terminal signal peptide and exhibits a more compact structure (61 aa) compared to other fibroin candidates in TSSM. Silk thread proteomes showed coordinated upregulation of protein folding, vesicle transport, and ATP-dependent processes in GSM, indicating an enhanced secretory infrastructure. Closely related spider mites utilize different dominant silk proteins. The more abundant and compact GRSP found in GSM silk threads may contribute to the formation of dense communal webs observed in this species. These findings suggest the evolutionary flexibility in silk protein composition among Tetranychusspecies in response to host adaptation.