EHIPIPTERYX. 209 



power must be weaker, and, their posterior tibiae being destitute of pallets, they are very 

 likely not so much aquatic, i. e. not such good swimmers as some of the Tridactyli. 

 Their lighter colour suggests, however, that they move about still more easily than 

 the latter on the surface of the calm water, helping themselves with their extended 

 wings *. 



In Rhipipteryx the cerci are obsoletely multi-articulate. The anal appendages of 

 the females are obsoletely parted in the middle ; the apical half being compressed, 

 dilated, and of ovoid form (Tab. XI. fig. 10). The last dorsal segment of the abdomen 

 of the males is frequently very abnormal in form, it being in some species much 

 widened and reflexed, i. e. strongly modified as in various Acridiidse. When this is the 

 case the cerci and the anal appendages remain small and slender (Tab. XI. fig. 22). 



The genus Rhipipteryx is peculiar to America ; it does not extend so far into the 

 temperate regions as Tridactylus. 



The parts of the mouth of Rhipipteryx having never been described, I give figures 

 of them: — Tab. XL : figg. 17, labium ; 18, maxilla ; 19, mandible. The labium much 

 resembles that of Tridactylus ; the third joint bears paraglossae, with membranous 

 apex (in Tridactylus these appendages are two-jointed). 



Synopsis specierum. 



a. Species majores, nigrse. Facies inter antennas ? £ plana. 



b. Totae nigrse, calcaribus tibiarum posticarum nigris. Oculi parum prominuli, invicem 

 valde remoti. 

 c. Antennae articulo 6° luteo. Metatarsus posticus gracilis, calcaribus aequilongus. Oculi 



posterius vix sinuati. — [1. forceps, sp. n.] 

 cc. Antennae articulis 8° et 9° luteis. Metatarsus posticus calcaribus subbrevior. Oculi 

 posterius distincte sinuati. — 2. carbonaria, sp. n. 

 bb. Flavo-variegatae, calcaribus tibiarum posticarum flavidis. Pronotum circumcirca flavo- 

 limbatum. Oculi invicem paulo propiores. 

 c. Pronoti discus utrinque linea obliqua flava. 



d. Elytra margine suturali flavo-limbato. Femora postica linea media flava nulla. 



(Statura praecedentium.) 



e. Oculi vix prominuli. Corporis picturse flavse angustae. Metatarsus posticus 



crassiusculus, quam calcaria tibiarum \ brevior. Appendices anales ($) 



grandes, toti nigri. Segmentum genitale £ supra planulum, margine sinuato; 



lamina supra-analis longe anguste producta, sulcata, acuta. — [3. brullei, Serv.] 



ee. Oculi g prominuli. Corporis picturae flavae latae. Metatarsus posticus ovato- 



conicus, quam calcaria ^ brevior. Appendices anales ( <$ ) cylindrici, graciles, 



apice flavi. Segmentum genitale <$ latissimum reflexum, angulis lateraliter 



acutissime productis ; lamina supra-analis utrinque transversa, strigata, parte 



media anguste producta, sulcata (fig. 22). — [4. cyanipennis, Sss.] 



* Amongst the Tettigidae, Scelimene seems to have similar hahits. 



biol. CBNTR.-AMER., Orthopt., December 1896. 2 Ee 



