In some places , harvestmen are known by the name `` daddy longlegs '' , but this name is also used for two other unrelated arthropods : the crane fly ( Tipulidae ) and the cellar spider ( Pholcidae ) . In some places , harvestmen are known by the name `` daddy longlegs '' or `` granddaddy longlegs '' , but this name is also used for two other unrelated arthropods : the crane fly ( Tipulidae ) and the cellar spider ( Pholcidae ) .