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In dealing with those insects that are suspected of conveying the disease 

 their possibilities in this connection are discussed. There are certain 

 conditions that must be fulfilled by any insect that can be considered 

 a possible vector. It must occur in abundance on sugar-cane in all 

 parts of the Island where, and when, the disease is spreading ; it 

 must be capable of rapid dispersion ; it must in all probabihty be 

 possessed of mouth-parts adapted to piercing and sucking the juices 

 of healthy cane, and it should live on that part of the cane-plant 

 where the infection occurs, i.e., on the central whorl of tender, growing 

 leaves. The weather and topographical conditions likely to influence 

 the occurrence both of the disease and of insects are briefly discussed. 



The pests dealt with include: — Acarina: Paratetranychus viridis, 

 Banks (green red spider) ; Damaeus nitens, Ewing ; and Tarsonemus 

 spinipes, Hirst (West Indian sugar-cane mite). Termites : Nastiti- 

 termes {Eutermes) morio, Latr. Orthoptera : Scapierisciis vicinus, 

 Scudd. (changa) ; Ellipcs minuta, Scudd. (little jumping changa) ; and 

 the grasshoppers, ScJiistocerca pallens, Thunb., Conocephalus cinereiis, 

 Thunb., and Neoconocephalns macroptents, Redt., of which the two 

 last-named, owing to their habits, suggest possibiUties of mosaic 

 transmission. Thrips, which may also be vectors. Rhynchota : 

 Lasiochiliis divisiis, Champ, (pink leaf-sheath bug) ; the Fulgorids, 

 Delphax (Stenocranus) saccharivora, Westw. (West Indian cane-fly), 

 observations on which record the most striking instance of an abundance 

 of recent secondary infection by mosaic disease where this species 

 predominated ; Megamelnsflavolineatus, Muir (yellow-backed Fulgorid) ; 

 Lihumia teapac, Fowl, (little black Fulgorid) ; Oliarus cinereiis, sp. n. 

 (grey Fulgorid) ; and Bothriocerus venosa. Fowl. ; and the Jassids, Agallia 

 tcnella, Ball ; TeUigonia occatoria, Say (coffee leaf-hopper) ; T. sirena, 

 Stal, which has probably been responsible for the first outbreak of 

 mosaic disease in several districts, infection being found wherever 

 it occurs ; Kolla ftiscolineella. Fowl. ; K. siniilis, Wlk., which is 

 probably the most abundant leaf-hopper in Porto Rico — its possible 

 connection with mosaic is discussed at length, observations showing 

 that it possesses all the characteristics considered essential for trans- 

 mission though its abundance does not coincide with the rapid spread 

 of the disease in the inland fields ; Draeculacephala sagittifera, Uhler 

 (large grey sugar-cane leaf-hopper) ; Spanghergiella vidnerata, Uhler ; 

 Deiiocephalus senilis, Uhler ; Athysaniis exitiosus, Uhler ; Thamnotettix 

 colonus, Uhler ; Erythroneuta comes, Say ; Scaphoideus fasciatus' Osb. ; 

 Cicadida sexnotata. Fall. ; two new species of Chlorotettix ; Balclutha 

 oshomi, Van Duzee ; and Empoasca mali, Le B. 



Other insects include the Aphids, Sipha flava, Forbes (yellow sugar- 

 cane aphis) and Aphis setariae, Thos. (black sugar-cane aphis) ; the 

 Coccids, Aclerda tokionis, Ckll. ; Targionia { Aspidiotiis) sacchari, 

 Ckll. ; Pidvinaria iceryi, Guer. ; and Psendococcus spp. — though the 

 last-named could only act as transmitters of mosaic in the event of 

 occasional transportation by ants to fresh plants ; the Lepidoptera 

 (which are scarcely possible transmitters, as they cannot obtain the 

 juice from uninjured cane), Diatraea saccharalis, F. (sugar-cane moth 

 borer) ; Opogona sp. (bud moth) ; Coleophora sp. (case-bearer) ; 

 Lapkygma frugiperda, S. & A., which may transmit mosaic, though 

 recently infected cane has never shown injury from this insect ; 

 Remigia pimctilaris , Hb. {repanda, F.) (sugar-cane looper cutworm) ; 

 and the sugar-cane skippers, Prenes nero, ¥., and P. ares, Feld., and 

 various other Hesperids ; the Diptera, Calohata lasciva, F. ; Euxesta 



