Mansonia Leberi, A New Mosquito from the Panama Canal Zone, with Notes on its Biology (Diptera: Culicidae)

The ♂, ♀, pupa, larva, and egg of Mansonia leberi , a new species of the subgenus Mansonia from the Panama Canal Zone, are described, illustrated, and compared with other indigenous Mansonia species. Associated rearings were made using Pistia stratiotes Linn, (water lettuce) as the host plant. Continuous fluorescent lighting was provided and 0.1 to 0.2 g of powdered tropical fish food were added to each of the 180 ml rearing cups every other day. The ♀ of M. leberi looks very much like that of M. indubitans Dyar & Shannon in regard to palp length and general coloration, but is similar to M. titillans (Walker), M. pseudotitillans (Theobald), and M. flaveola (Coquillett) in having a row of stout spines on abdominal tergite VII and a central group of contiguous spines on abdominal tergite VIII. As M. indubitans does not have these characteristics, M. leberi is considered to have closer phylogenetic relationships with the latter 3 species. The ♂ of M. leberi is distinguished by the prominent angular external crest on its claspers. The abdominal hairs of the pupa are longer than those of M. indubitans and its shorter trumpets have dark brown dorsal patches. The double, blade-like hairs of the siphon tuft characterize the 4th-instar larva. The dark brown to black eggs of M. leberi are slightly smaller than those of M. indubitans and M. titillans but are somewhat similar in general shape and color. The tapered, lightly pigmented tips of M. leberi eggs are equal to about 1/5 to 1/6 of the total egg length whereas those of the other 2 species are nearly 1/3 of the total length. Mansonia titillans eggs taper gently to their apices forming broader tips than those of M. indubitans which taper abruptly forming uniformly slender tips. Immatures of M. leberi have been collected almost exclusively from either Luziola subintegra Swallen (aquatic grass) or Cyperus sp. (sedge) and have been most commonly found in association with larvae of M. titillans and Coquillettidia nigricans (Coquillett). Adults bite man and horses actively at night and continue to attack collectors during the day in heavily-shaded forest regions. This species reaches its greatest abundance, as evidenced in horse-baited trap collections, from July through October during the peak of the rainy season. Except for a single ♀ collected at Cocoli, Canal Zone on the Pacific side of the Isthmus and another ♀ taken on San Jose I. in the Gulf of Panama, M. leberi is presently known only from the Chagres River from Gamboa, Canal Zone to the confluence of the Chilibre River near the Panama border, and from certain regions of the Chilibre River within the Canal Zone.