In proceedings to invalidate petitions designating John A. De Rario and Wilfred Manzo as candidates of the Homeowners, Tenants and Taxpayers Party in the general election to be held on November 8, 1977 for the public offices of County Legislator, 12th and 13th Legislative District, Westchester County, the appeal is from an order of the Supreme Court, Westchester County, dated October 4, 1977, which denied appellants' motion to dismiss the proceedings for lack of jurisdiction. Order reversed, on the law, without costs or disbursements, motion granted and proceedings dismissed. These proceedings were commenced by an order to show cause, signed on September 2, 1977 and returnable on September 27, 1977. On September 2, 1977 the petitioners-respondents mailed copies of the order and accompanying petition to the appellants. Although the order to show cause contained language concerning service by mail, the space provided for indicating the final date for service by mail was left blank. Dates were inserted in all other blanks. The absence of a date for final mailing had the effect of striking the provision for substituted service. Therefore, the mode of service utilized by the petitioners was not in strict compliance with the order to show cause and, since this is a jurisdictional defect, we are constrained to reverse (see Matter of Bruno v Ackerson, 51 A.D.2d 1051, affd 39 N.Y.2d 718). Hopkins J.P., Latham, Margett and Rabin, JJ., concur.