FlyBase curator comment: The P{?'lArB} entry in FlyBase is used to denote the transgenic construct present in an insertion when it is known that the inserted element is a deleted version of P{lArB} (generated during transposition/excision), and where it is known that the deletion removes one end of the P{lArB} element, but it is not known which transposable-element end has been removed (this includes cases where a single terminal repeat is all that remains). For details of what portion of the original P{lArB} element remains for an individual insertion of P{?'lArB}, see the description in the insertion report and/or in any allele reports associated with that insertion.