The JapanSocietyJapan Society ofMedicalEntomologyof Medical Entomology and Zoology (Jap･ J, Sanit.Zool,Vol. 32 No,4 p. 301-3081981) Blaekfiies (Diptera: Simuliidae) in highland streams in Guatemala, with special referenee to the seasonal immature prevalenee of stages and voltinism' Takao OKAzAwA*' and Hirosi TAKAHAsl"* ** Biolo.oical Institute, Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060. JaPan *'* Ha)'amiya I-40-IO, Nerima-ku, Tokyo l76, JaPan (Received: June 18, 1981> Abstract: Immature stages of were studied uppermest of blackflies in part 2 streams in Guatemalan highland, Sierra Madre. In total 5 species, Gigantodax tt'righti., Simulium (Simttlium) tricornis, S. (S.) anduJei and S. (S.) fobbinsi in descending order of abundance, were collected. G, terTi.ohti and S. (E.) sp. svere preclominant and occupied more than 80% of the total specimens collected from each stream, All the 5 species appeared at higher density in the rainy season and the first half of the dry season than in the Iatter half ef the dry season. From thc head width distribution in each month, G, wrighti and S. (E.) sp. were found to be multivoltine species. G. tt]righti had two generations in the rainy season to the first half of the dry season and possibly one generation in the latter half. S. (E,) sp, had 2 generations in the rainy season, and at least one more generation, possibly two, Ln- r.he dry season. Many studies on seasonal prevalence, ciasis, In the present paper tropical highland growth and ]ife history of blackflies have blackflies in Guatemala were studied on sea- been undertaken (Sommerman et al., 1955; sonal prevalence of immature stages and Davies and Syme, 1958; Ladle and Esmat, voltinism, including a species of the genus Gi- 1973; Hansford, 1978; Wotton, 1978 etc.), gantodax. Gigantodax is one of the phylo- but intensive studies have been restricted to genetically interestin.rr. genera, which is dis- the middle and high latitudes of the northern tributed from the southern end of South hemisphere. Little has been studied on Meso- America to Mexican highland along the ameriean and Southamerican species except Andes and bevond the Isthmus of Panama. " for the vecter species of human onchocer- '-g ' STuDY AREA AND IV(ETHoDs This study was supported by the Ministry Collections were made in streams, of Public Health, Guatemala and Japan 2 the International Cooperation Agenc>' CJICA). Tzojoma and the Sesenta Vueltas in Guate- GJCRCPO-MENSAP Series No.40 malan highland, Sierra Madre, located north ** Present address: Department of Microbielogy, of Lake AtitilEn as shown in Fig, 1. Both 840- Saga Medical College, Nabeshima, Saga streams are small tributaries and rise near Ol, Japan the ridge of the mountains, which has almost ** ,trr e; "}f: i; ma V" if kit : L[L me Jl< if ss glj #va tw S (+ 060 Tr 3,OOOm of altitude. They fiow for about *L Nrti tiic rK :k 10 ec ut 8 fi ) 100 m from the source on the gently inclined -trJfi: iZlesXT+Jit#dilktz#XS (+840-Ol slopes, then run down along the steep slopes iL{ es Tti S& E =- lr Ef ) *** to the with the main rivers. Sam- t･-･-,ts i.･L: (+176 MA'XEkt.eeIg41El-40-iO)301 junctions NII-Electronic Library Service The JapanSocietyJapan Society of MedicalEntomologyMedical Entomology andandZoology Zoology 302 Jap. J. Sanit. Zoel. 2seo Fig. 1 Topography of study area Arrows indicate the sampling sites, A: the Tzojom5 Stream. B: the SesentaVueltas Stream, pling sites were chosen in the uppermost, were about 15 and 3 cm, respectively. Month- gently inclined part. The sampling site in ly change of mean maximum and minimum the Tzojoma (A) is close to the highest point temperatures and precipitation in Totonica- of the Central American Road No.1 be- pan are shown in Fig.2. The maximum tween Nahua15 and San Cristobal Tetonica- temperature is almost constant throughout paii, where the departmental border line the year. The minimum temperature is vari- between Solola and Totonicapan lies. The able, being higher in the rainy season than Sesenta Vueltas crosses the National Road in the dry season. The water temperature in No. 1 about 6km from Encuentros to Toto- nicapan. The site is situated at upstream of the crossing. AItitudes of the sites in the Tzojoma and the Sesenta Vueltas are 2,9eO mmoe and 2,850m, respectively. The site in the c Tzojoma is surrounded by and ,9 grassland -tu00 wheat fields, and the site in the Sesenta -" ,g Vueltas by grassland with low shrubs and g ioe vegetable fields. The stream-bed consists of hard mud. Short hydrophilous grass grow out of water along the margins of the streams, JFMA MJJASOND The width and depth of the streams in the Month seasen of maximum water discharge were Fig. 2 Mean maximum, minimum tem- about and 40 10 cm respectively, while in the and peratures precipitation during 1954- season of the minimum water discharge, they 1959 at Totonicapan NII-Electronic Library Service The JapanSocietyJapan Society of Medical Entomology and Zoology Vol. 32 No. 4 1981 303 the Sesenta Vueltas was constant,, approxi- by Okazawa in November 1977 to October mately 120C irrespective of time of measure- 1978, and 1 sample by Takahasi in Novem- ment, except March 1979, when it was 160C. ber 1978 to June 1979. All specimens col- The temperature in the Tzojoma fluctuated lected were kept in 70% ethanol, After between 11 and 170C, with a tendency to- species identification, head widths of all Iar- wards being cooler in January to February vae were measured. and warmer in April to December. The val- ]ey of Tzojema faces southwest and is sur- REsuLTs rounded by grassland, therefore the isola- afternoon rnay affect species and number of col- tion in the the ground The individuals and water temperatures, while the valley of lected are shown in Table 1. In total, 5 the Sesenta Vueltas faces east, resulting in species belonging to 2 genera were collected, rather constant water temperature. In the TzojomE, Simulium (Eusimulium) sp. The rainy season generally begins in May was the most abundant and was followed by and ends in October. Increasecl water dis- Gigantodax ietrighti and Simulium (Simu- charge was observed 1 or 2 months after the lium) tricornis in descending order, while beginning of the rainy season. The decrease in the Sesenta Vueltas, G. wrighti was the was observed also 1 or 2 months after the most abundant followed by S. (E.) sp,, S. end of the rainy season (Figs,2 and 3). In (S.) tricornis, S. (S.) andu2ei and S. (S.) the later half of the dry season, Ns'ater leveJ 1'obbinsi. G. zvrighti and S. (E.) sp. were was very low, with only a slight trickle of predominant species,' a total of the 2 species water, occupying more than 99% ef the total speci- of mens collected and For inve$tigation seasonal prevalence, in the Tzojoma 81flcin a unit time collection was adopted. Larvae the Sesenta Vueltas, and pupae attached to submerged plant mat- Seasonal prevalence of each species is ter were collected by forceps for ]Omin. shown in Fig.3. G. wrighti was abundant Thoroug.h searching for sirnuliids on each during the period from the rainy season to substrate was made to avoid the bias to larg- the first half of the dry season, but scarce er individuals onlv which are easier to find in the latter half of the dry season. It seems - out and pick up, Once collection was started that there existed 3 peaks in abundance, 2 with a substrate, it continued till all simuliid of them in the rainy season and 1 in the dry Iarvae were completely picked up from the season. However, at the Sesent Vueltas dur- same substrate, then another substrate was ing the rainy season only 1 blunt peak in taken. Samplin.cr was carried out once a July to October was observed. A]l the peaks month. cach samples were appeared At time 2 taken in the SesentaVueltas laterthan Table 1 Number of blackfly larvae and pupae collected in 2 streams in highland Guatemala during a period ef 1 year, from November 1977 to October 1978 in the Tzojoma Stream and from May 1978 to April 1979 in the Sesenta Vueltas Stream Tzojomi (A) Sesenta Vueltas Spccies No. of (B) Ne, of Larvae Pupae %* Larvae Pupae %* Gigantodax wrighti Vargas, )vlartines and DEaz 945 6ooo172337.0 1,399 IO 66.3 Simulium (Simutium) anduzei Vargas and D{az o O 98 4 4.8 Simuliurn (Sinzulium) J'obbinsi Vargas, Martinez and Diaz o O 89 2 4,3 Sin!ulium (Simuiium) tricornis De Le6n 21,601 O.1 203 O 9.5 15.1100.0 Simulium (Eusimutium) sp. 62.9 309 11 Total 2,S48 100.0 2,09827 ' Percentage of number of larvae and pupaeto the totalcollections. NII-Electronic Library Service The JapanSocietyJapan Society of Medical Entomology and Zoology 304 Jap. J, Sanit. Zool. ttttttttt .:[,.,,.."::,.)ctt;S:;,V,k,V..t,{/tl'ttlt wL!lgtt!!ltlll'L'i'il,i".l:[lii'f'1/')'1',l'l't':),C-AT2ejomA 180G;antdaxttttttt L.lyfSS, ±."..,- "i,};].l{'fiil,Slt/IIIil}{':.,lii`l{[I[-Bsesentavueltas 150120906030 l fi } .S..Pv'S[ tttt.\,.f.Z,l.ft.tt..::S/.s...... oa>Le-oLdinE=zo150$imuliumsp.I;ltl'//{t'lil,l'/II[ll1/,ill'illl://ll'i;/l'l-A .tCt)tt))!tCtt:ttAttt.. ll'/1/Ll'll/1/:1/Il,lttt, "'"t#')'.'.'s\v'sul':'::"=[" /ti･;']...[.lie='C';[l[:ill;'t;1{/llt:, B 120 {/:.",;･.g'llll'I{I･,l'illl･i･l,:i*E:i･.I'1.l/ii'l/1/l/l?l･l･i･ 9060 /lill,I:･1･1/llil}:::.i,li};.i:Ill,ltl' :･l'i//･i',riC;i, :,ls;i}li･ls ll',･l]'I):･:ll,li",jiil･l,l;llli･i.'if't･ii.I･i; {t.'s-':',i}i,}1:El.lIi;',,:l/1:,l.it ttt 30 t]././tt.;..ttlt.ttttt.t.