Journal of the American Control Association, 15(3):271_2.:5, 1999 Copyright O 1999 by the American Mosquito Control Association, Inc.

MOSQUITO IMMATURES IN DROUGHT-PRONE AND DROUGHT-RESISTANT BAMBOO STUMPS IN FLORES,

TOSHIHIKO SUNAHARA,I MoToYoSHI MOGII INo MAKMUR SELoMo,

ABSTRACT _ Mosquito species in water-filled bamboo stumps were compared with those emerged from dormant eggs in dry stumps. Tripteroides spp. was more abundant than Aetleslstegomyia) spp. (mainly annan- dalei and albttpictus) in water-filled stumps, whereas the latter was more abundant than the former in dry stumps. During 5 days after inundation, Aedes (Stegomyia) spp. developed faster than Tripteroides spp. Density of Tripteroides spp. was high in narrow and deep stumps. Both taxa of mosquitoes were at low deniities in water- filled stumps with large detritivores (Tipulidae and Oligochaeta).

KEY WOR"DS Aedes, habitat segregation, mosquito community, species interaction, Tripteroitles

INTRODUCTION retained water in the dry season with those that emerged from dormant eggs in dry stumps. Several container-breeding mosquito species of- In addition to drought susceptibility, we exam- ten co-occur in the same locality without competi- ined effects of the stump morphology and presence tive exclusion. Their coexistence can be attributed of predators and large detritivores on habitat uses at least partially to habitat segregation, which re- of mosquitoes. These habitat conditions vary sults from differential specialization of mosquitoes among stumps and may affect the use of bamboo under variable habitat conditions. stumps by mosquitoes. Drought susceptibility is one of the conditions that may result in habitat segregation of mosqui- toes. Drought susceptibility varies among tree MATERIALS AND METHODS holes, bamboo stumps, and other artif,cial contain- Sampling was carried out in 7 sites near villages ers (Bradshaw and Holzapfel 1988, Sota et al. along the road from Ende City (8"48'5, l2l"4l'E) 1994, Sunahara and Mogi 1997a). Some mosqui- to Mount Keli Mutu, East Flores, in August 1997. toes, such as Aedes spp., whose eggs are highly Elevations of the 7 sampling sites were 70, 460, resistant to desiccation, specialize on drought-prone 700, 800, 960, 99O, and 1,070 m. Wet months with containers, whereas others cannot breed success- rainfall more than 100 mm are from November to fully in these habitats. ln tree holes in Florida, Ae- April in Ende (Monk et al. 1997). Although the des triseriatus (Say) uses drought-prone holes suc- sampling period was during the dry season, some cessfully, whereas breeding of other mosquitoes, rainfall occurred in the mountainous area. We such as Orthopodomyia signiftra (Coq.) and pre- found water-filled bamboo stumps at the 5 sites in daceous Toxorhynchites rutilus (Coq.), is limited to the mountainous area (elevation, 700-1,070 m), but drought-resistant holes (Bradshaw and Holzapfel not at the 2 sites in the lowland (70-460 m). 1983, 1988). In bamboo stumps in southwestern Ja- Forty-fi ve water-fi lled stumps (probably B ambu- pan, Aedes albopictus (Skuse) and Tripteroides sa spp.) were cut from the 5 sites in the mountain- bambusa (Yamada) are predominant in drought- ous area and brought to a laboratory in Ende City. prone and drought-resistant stumps, respectively For each stump, we measured the long (d,) and the (Sunahara and Mogi 1997a). Similar situations gen- short (dr) inner diameters (d, ranged from 2.3 to erally may occur in many localities where both I1.0 cm), and calculated the opening area as ddrnl drought-prone and drought-resistant containers ex- 4. We measured depth of the stumps (from the cut ist. to the bottom; ranged, 7.1-26.2 cm). Water volume This paper deals with mosquito communities in in the stumps ranged from 5 to 4O2 ml (no data for bamboo stumps in Flores Island, Indonesia. Al- 8 stumps). All and earthworms inside though a high diversity of mosquitoes in bamboo stumps were collected and preserved with 1O7ofor- stumps has been reported from Southeast Asia malin, except for some mosquito larvae and pupae (Sota 1996b), their habitat segregarion has not been that were reared to adults for identification. The investigated in detail. Our main purpose is to de- 3rd- and 4th-stage larvae and adults of mosquitoes scribe patterns of use of drought-prone and were identified to species or genus. Identification drought-resistant bamboo stumps by mosquitoes. followed Huang (1979) and Mattingly (1971, 1981). We compared the mosquito species in stumps that Individuals that died during rearing were not included in the number of individuals recorded for each species. I Division of Parasitology, Department of Microbiology, From 6 sites (elevation, 7O-1,070 m), 38 dry Saga Medical School, Saga 849-8501, Japan. bamboo stumps that were considered to have con- 2 Faculty of Public Health, Hasanuddin University, tained water (with black sediments in the bottoms) Ujung Pandang, Indonesia. were cut and broueht to the laboratorv. There. we

271 272 Jounral oF THE AMERIcIN MosQurro Coltrnol AssocrATIoN Vor. 15.No. 3

Table l. Frequencies of occurrence and abundance of mosquito immatures in 45 water-filled bamboo stumps.

No. Density positive per cm' Total no. Mosquito stumps Proportion (mean + SE) immatures

Detritivore Aedes ( Stegomyia) annandalei l0 o.222 0.054 + 0.029 43 A ede s ( Steg omyia) ttlbop ictus 9 0.200 0.024+ 0.011 3L Aedes (Stegomyia) scutellaris 1 o.022 0.001+ 0.001 I Aedes (Finlaya) sp. I I 0.o22 0.003 + 0.003 A Aedes (Finlaya) sp. 2 I o.o22 0.002 r 0.002 4 Tripteroides sp. 1 l8 0.400 o.24'/ * O.O90 168 Tripteroides sp. 2 t4 o.3lI 0.078+ 0.035 7l Armigeres sp. 3 0.067 o.lt3 + 0.072 198 Ficalbia sp. 3 0.067 0.014+ 0.004 2I Culex (Culiciomyia) sp. 1 o.o22 0.004 + 0.004 6 Orthopodomyia sp. I o.022 0.001+ 0.001 2 Carnivore Toxorhynchites sp. 0.200 0.008 + 0.004 t2 filled them with well water and placed them under curred in high densities in 3 stumps (27-137 indi- eaves. The stumps were covered with mesh sheets viduals per stump), the 2 species of Tripteroides to prevent the entry of mosquitoes. Five days later, were predominant in frequency of occurrence and 13 of these stumps retained water but the rest had density (number/cm'). The combined density of im- lost water due to leaks. For each stump with water, mature Tripteroides spp. was significantly higher we measured d, (range, 3.2-8.0 cm) and depth than that of immature Aedes (Stegomyta) spp. (Wil- (range, 9.6-23.8 cm). Water volume ranged from 4 coxon's signed rank test, Z = -2.763, P < 0.01). to 145 ml (no data for 1 stump). All insects in the In addition to mosquitoes, detritivorous lar- 13 stumps were collected and mosquito larvae were vae such as Tipulidae (10 stumps), Helodidae (6 identified according to genus. The number oflarvae stumps), Ceratopogonidae (18 stumps), Chironom- in each developmental stage was counted for each idae (14 stumps), and Psychodidae (8 stumps) were mosquito genus. Some of the larvae of each genus collected. Of these, Tipulidae were the largest in found in each stump were allowed to develop to body length (maximum length, 38 mm). Other un- the 3rd instar or further for identification. The re- identified dipteran larvae were found in 10 stumps. mainder were fixed with IOVo formalin. We esti- In addition, large individuals of Oligochaeta (max- mated the number of individuals of each species of imum length, 50 mm) were found in 8 stumps. a genus assuming that the proportion of each spe- Mosquito larvae emerged from dormant eggs in cies in the identified samples was equal to that in all of the 13 stumps that retained water for 5 days. the total individuals on the 5th dav after inundation. From these stumps, 5 mosquito species of the gen- era Aedes and Tripteroides werc collected (Table RESULTS 2). In addition to the mosquito larvae, larvae of Ceratopogonidae (5 stumps), Helodidae (1 stump), Comparison of wet and dry stumps and Tipulidae (1 stump) were collected. The 2 spe- From water-filled stumps, 12 species of 7 genera cies of Aedes (Stegomyia) were predominant in of mosquitoes were identified (Table l). These in- terms of frequency of occurrence and the density. cluded 1 carnivore, Toxorhynchites sp. Detritivo- The combined density of Aedes (Stegomyia) spp. rous irnmature mosquitoes were found in 36 stumps larvae was significantly higher than that of Tripter- (8OVo). In addition to Armigeres sp., which oc- oides spp. larvae (Wilcoxon's signed rank test, Z :

Table 2. Frequencies of occurrence and abundance of mosquito larvae that emerged from dormant eggs in 13 dry bamboo stumps-

No. Density positive per cm2 Total no. Mosquitoes stumps Proportion (mean SE) larvae

Aedes ( Stegomyia ) annandalei 8 0.615 1.243 + 0.460 229 Aedes (Stegomyia) albopictus 9 0.692 o.460 + 0.779 135 Aedes (Finlaya) sp. I o.o77 0.020 + 0.020 12 Tripteroides sp. I 6 o.462 0.426 + 0.258 57 Tripteroides sp.2 5 0.385 0.266 + 0.207 31 Ssprerrassn1999 Mosqutro Ilruetunr CoulauNrry rN Bevnoo Srrnaps 273

Table 3. Number of immatures in each de stage in dry stumps at the 5th day from inundation

Mosquitoes lnstar I Instar IV Pupa

Tripteroides spp. I 72 I) I 0 Aedes (Stegomyia) spp 0 58 r37 162 0

-2.197 , P < 0.05). Except for Aedes (Finlaya) sp., 5). The difference in densities between stumps with which occurred only in I stump collected at 990 m, and without the large detritivores was significant these mosquitoes occurred both in low-elevation for Tripteroides spp. and Aedes (Stegomyia) spp. (70-460 m) and high-elevation (700-1,070 m) sites. Their rank order in terms of the density of DISCUSSION larvae was the same as that in Table 2 both in the low- and high-elevation sites. The predominance of aedine mosquitoes in By the 5th day after inundation of the dry drought-prone sites has been reported previously stumps, development of larvae of Aedes spp. was (Bradshaw and Holzapfel 1988; Sunahara and Mogi more advanced than that of Tripteroides spp. (Table 1997a, 1997b). The greater abundance of Aedes 3). The proportion of the 3rd- and 4th-stage larvae (Stegomyia) spp. than Tripteroides spp. in dry of Aedes spp. was significantly higher than that of stumps in our results is due to the greater input rate Tripteroides spp. (Fisher's exact probability, P < and/or higher survival rate of Aedes (Stegomyia) 0.001). The 4th-stage larvae of Aedes spp. were spp. eggs. Aedes (.Stegomyia) spp. lay eggs on con- found in 9 of I I Aedes-positive stumps, whereas tainer walls above the water line. Their desiccation- only I 4th-stage larva of Tripteroides sp. was found resistant eggs survive in dry containers and hatch in 1 stump out of 9 Tripteroides-positive stumps immediately after flooding. On the other hand, (difference in the proportion of stumps with 4th in- Tripteroides spp. lay eggs mainly on the water sur- stars: Fisher's exact probabllity, P < 0.01). face and eggs hatch without delay (Miyagi 1973, Okazawa et al. 1985). Tripteroides eggs have been reported to have some degree of desiccation resis- Stump morphology tance (Miyagi 1973, Okazawa et al. 1985, Sunahara The relationship between stump morphology and and Mogi 1997c). However, Okazawa et al. (1985) density (number per area) was different between showed that no eggs of Tripteroides aranoides Aedes (Stegomyia) spp. and Tripteroides spp. (Ta- (Theobald) survived more than 40 days at SOVorel- ble 4). Both in water-fllled and dry stumps, density ative humidity and 2O'C. The relative predomi- of Tripteroide.r spp. was negatively correlated with nance of Aedes (Stegomyia) spp. to Tripteroides the area of the opening. In water-fllled stumps, den- spp. in drought-prone stumps might be due to the sity of Tripteroides spp. was positively correlated difference in desiccation resistance of eggs, as well with the depth of the stump. Density of Aedes as in preference of oviposition sites between the 2 (Stegomyia) spp. was not correlated significantly groups. with either area or depth in both water-filled and In addition to their predominance in abundance, dry stumps. Aedes (Stegomyia) spp. had a faster rate of larval development in the dry stumps 5 days after inun- dation. Aedes alboplcrus (Skuse) develops faster Presence of predators and large detritivores thart Tr. bambusa (Sunahara and Mogi 1997b). Densities of the immature mosquitoes were Probably the difference in the stage structure at the smaller in stumps with 4th instars of Toxorhynchi- 5th day after inundation between Stegomyia spp. tes sp. than in stumps without them, although the and Tripteroides spp. was due to the difference in difference was significant only when all detritivo- growth rate. However, hatching times may also rous mosquitoes were pooled (Table 5). The num- have been different between the 2 groups. Rapid ber of immature mosquitoes was significantly hatch and/or development after flooding can en- smaller in stumps with large detritivores (Tipulidae hance the probability of completing larval devel- or Oligochaeta) than in stumps without them (Table opment before the stump dries up. Moreover, fast

Table 4. Spearman's coefficient of rank correlation (r,) between densities of mosquitoes and morphologic characteristics of bamboo stumps. I

Water-filled stumps Dry stumps Mosquitoes Depth Depth

Tripteroides spp. _0.537*** 0.395*+ -o.767** 0.119NS Aedes (Stegomyla) spp. -0.225 NS 0.199NS -0.278NS -0.438 NS JoURNAL or rue Ausntcau Mosqutro Cournol AssocIATIoN Vor. 15,No. 3

C) developers have an advantage over slow developers in exploiting competition within a single generation O Orl because the greater body size of fast developers is EEE associated with higher feeding rates (Chambers eB" 1985, Sunahara and Mogi 1997b). Tripteroides spp. or other mosquitoes possibly colonize drought- prone stumps after rain water fills them. However, because of the time lag between oviposition and hatching, Aedes (Stegomyia) spp. larvae that d s ia{ ts emerge from dormant eggs should have an advan- A A-i tage in the use ofnew aquatic sites, at least initially. otl +r +t+ Thus, the greater abundance and more rapid devel- o \or) O\ +cn opment suggests that Aedes (Stegomyia) spp. use Fi AA drought-prone stumps more efficiently than do s Tripteroides spp. In water-filled stumps, Tripteroides spp. were predominant to Aedes (Stegomyia) spp. in frequen- oo f- n6 o\ r)* cy of occurrence and density. Because we did not J ' :€ A .i-i check the egg pools in water-filled stumps, it is not bN +r +t+l clear whether the relative predominance is the same {s in the rainy season, when water levels increase and € r)* dormant eggs above the water line hatch. ; A j-i The genus Tripteroides is distributed widely in the Oriental region (Mattingly 1981). The result of o the present study is similar to that of Sunahara and o Mogi (1997a) who found that Tr. bambusa was pre- r h- b0 d26 dominant in drought-resistant bamboo stumps in o E.!s southwestern Japan. Tripteroides spp. are also the E 28" V) (h B zz main constituents of mosquito communities in wa- o ter-filled bamboo stumps in North Sulawesi, Indo- Ttl nesia (Sota 1996b). Predominance of Tripteroides (h ia spp. in drought-resistant containers may be ob- served generally in the Oriental region. \o ** d a Aedine mosquitoes have been reported to be in- A -i^i E ferior to others in using permanent aquatic sites be- 6l + +t+1 iR n €* cause of their high susceptibility to predation 0 O\ no (Bradshaw and Holzapfel 1983, Chambers 1985), A -i^i a and low survival and growth rates under limited F food conditions (Sunahara and Mogi 1997b). These disadvantages might partially contribute to the low t frequency and density of Aedes (Stegomyia) spp. in $ o€ d r,N!1 water-filled stumps. r :co A AA Although Tripteroides spp. seem to use water- o -o tl +t +t tl filled stumps more efficiently than other mosqui- (s toes, they did not use all stumps evenly. The den- o ct t\ o\ -i -iA sity of Tripteroides spp. immatures was positively correlated with depth of the stump, and negatively correlated with opening area. Tripteroides spp. were suggested to prefer nrurow and deep stumps. Such a preference of Tripteroides has been reported o previously (Sota N 1996a, Sunahara and Mogi 1997a). The opening area and depth of the stump gB may be correlated with habitat quality, such as per- 'r sistence of the water body. F-- ..8 The use of water-filled stumps by Tripteroides E 3Fi spp. and other mosquitoes also seemed to be lim- (J O q:^ .z *i' ited by presence of predators and large detritivores. .F x- Toxorhynchites is the most important predator in x: a , ao container habitats. The density of mosquito imma- f !c :zz - .s\ tures was lower in Toxorhynchites-positive stumps F < r+ than in stumps without Toxorhynchites. The differ- SeprEveen1999 Mosquno IMMATURECouruuNrrv nq Be.ugoo Srrmps 215 ences in mosquito densities was greater between shop. Florida Medical Entomology Laboratory, Vero stumps with and without large detritivores. These Beach, FL. differences might be the result of exploiting com- Heard, S. B. 1994. Processing chain ecology: resource petition between large detritivores and mosquitoes, condition and interspecific interaction. J. Anim. Ecol. 63:451-464. or interference. Recent studies have reported the Huang, Y. M. 1979. Medical entomology studies-Xl positive effects of shredders on mosquitoes or The subgenus Stegomyia of Aedes in the Oriental region midges via the processing chain (Bradshaw and with keys to the species (Diptera: Culicidae). Contrib. Holzapfel 1992, Heard 1994, Paradise and Dunson Am. Entomol. Inst. 15(6):1-78. 1997). The present study suggests the possible neg- Mattingly, P E 1971. Contributions to the mosquito fauna ative effect of the large detritivores on mosquitoes. of Southeast Asia XII. Illustrated keys to the genera of To summarize, the present study showed that use mosquitoes (Diptera, Culicidae). Contrib. Am. Entomol. of bamboo stumps by mosquitoes was limited by Inst. 7(4): l-84. Mattingly, P E 1981. Medical entomology studies-XlV. drought susceptibility, stump morphology, and pos- The subgenera Rachionotomyia, Tricholeptomyia and sibly interactions predators with and large detriti- Tripteroides (Mabinii group) of genus Tripteroides in vores. Use of bamboo stumps by Aedes (Stegomyia) the Oriental region (Diptera: Culicidae). Contrib. Am. spp. and Tripteroides spp. was differentially limited Entomol. Inst. 17(5):1-147. by these factors. Such variable responses of mos- Miyagi, l. 1973. Colonizations of Culex (Lophocera- quito species to habitat conditions can result in hab- omyia) infantulas Edwards and Tripteroides (Tripteroi- itat segregation and enhance coexistence of mos- des) bambusa (Yamada) in laboratory. Trop. Med. 15: quitoes in bamboo stumps. 196-203. Monk, K. A., Y. D. Fretes and G. Reksodiharjo-Lilley. 1997. The ecology of Nusa Tenggara and Maluku. Per- ACKNOWLEDGMENTS oplus Editions, . Okazawa, T,, M. Horio, M. Mogi, I. Miyagi and S. Su- We are grateful to R. Ngatimin of Hasanuddin charit. 1985. Laboratory bionomics of Tripteroides ar- anoides. J. Am. Mosq. University, the Head of LIPI (Indonesian Institute Control Assoc. l:428-434. Paradise, C. J. and W. A. Dunson. 1997. Insect species of Science), and Basri Hasanuddin, the rector of interactions and resource effects in treeholes: are hel- Hasanuddin University, for supporting our study. odid beetles bottom-up facilitators of midge popula- We appreciate helpful comments on this manuscript tions? Oecologia 109:303-3 72. by the 2 anonymous reviewers. This study was sup- Sota, T, 1996a. Effects of capacity on resource input and ported by a grant-in-aid from the Monbusho Inter- the aquatic metazoan community structure in phytotel- national Scientific Research Program (Field Re- mata. Res. Popul. Ecol. 38:65-73. search) (grant 08041 197). Sota, T, 1996b. Species richness and altitudinal variation in the aquatic metazoan community in bamboo phyto- telmata from North Sulawesi. Res. Popul. Ecol.38:2'15- REFERENCES CITED 281. Sota, T., M. Mogi and E. Hayamizu. 1994. Habitat stabil- Bradshaw, W. E. and C. M. Holzapfel. 1983. Predator- ity and the larval mosquito community in treeholes and mediated, non-equilibrium coexistenceof tree-hole other containers on a temperate island. Res. Popul. mosquitoesin southeasternNorth America. Oecologia Ecol. 36:93-104. 5'l:239-256. Sunahara, T, and M. Mogi. 1997a. Distributions of larval Bradshaw,W. E. and C. M. Holzapfel.1988. Drought and mosquitoes among bamboo-stump pools which vary in the organization of tree-hole mosquito communities. persistence and resource input. Res. Popul. Ecol. 39: Oecologia74:5O7-514. 173-180. Bradshaw, W. E. and C. M. Holzapfel,. 1992. Resource Sunahara, T. and M. Mogi. 1997b. Can the tortoise beat limitation, habitat segregation,and speciesinteractions the hare?: a possible mechanism for the coexistence of of British tree-holemosquitoes in nature.Oecologia 90: the competing mosquitoes in bamboo groves. Ecol. Res. zzt-zJt. l2:63J0. Chambers, R. C. 1985. Competition and predation among Sunahara, T. and M. Mogi. 1997c. Drought and overwrn- larvae of three species of treehole-breeding mosquitoes, tering success of Tripteroides bambusa (Diptera: Culic- pp.25-53. In: L. P. Lounibos, J. R. Rey, and J. H. Frank idae) larvae and eggs in a bamboo grove. Med. Ento- (eds.). Ecology of mosquitoes; Proceedings of a work- mol. Zool. 48:295-3O2.