Population Biology

and do not harm nontarget organisms.) All the exposed insects are stunned and fall to the ground, where they are collected, identified, and counted. In this way, almost complete samples can be taken. Cockroaches (Fisk 1982), wax bugs (Wolda 1980), grasshoppers (Roberts 1973), and carabid beetles (Erwin 1983) have been analyzed.

Some comparisons of species richness of temperate rheophilic (Stout and Vander-meer 1975) forms to those in Costa Rican and Andean (Patrick 1966) streams have been made. Results generally show that midlatitude stream faunas are significantly more diverse than those in comparable, high-latitude streams.

Soil and litter types are studied by means of the Berlese (Tullgren) funnel (Beebe 1916). Samples may also be taken with a core auger and separation by flotation in liquid suspensions. Substrata may be experimentally manipulated, which allows the investigator to measure minute habitat characteristics with great accuracy and compare them to natural plots (Stanton 1979).

From these various population studies, it is generally conceded that in tropical forests, insect abundance is low but the diversity very high. It seems also that the dispersion of insect populations over a particular area is seldom even but usually very patchy. This may be caused by the irregular distribution of habitats (Wiens 1976), but it can be so even if environmental needs appear continuously and abundantly available. Moisture content of litter and soil may be very unevenly distributed, for example, and a major factor affecting the presence or absence of ants, springtails, mites, and other arthropods (Levings and Windsor 1984). However, in spite of the enormous numbers of leaves available on a single tree or in a forest, only a few are normally utilized by herbivores at one time (notwithstanding population explosions when defoliation may occur).

References

Adis, J. 1977. Programa mínimo para análises de ecosistemas: Artrópodos terrestres em florestas inundáveis da Amazonia central. Acta Amazónica 7: 223-229.

Allan, J. D., L. W. Barnhouse, R. H. Prestbye, and D. R. Strong. 1973. On foliage arthropod communities of Puerto Rican second growth vegetation. Ecology 54: 628-632.

Beebe, W. 1916. Fauna of four square feet of jungle debris. Zoologica 2: 107-119.

Ehrlich, P. R., and L. E. Gilbert. 1973. Population structure and dynamics of the tropical butterfly Heliconius ethilla. Biotropica 5: 69-82.

Elton, C. S. 1973. The structure of invertebrate populations inside Neotropical rain forest. J. Anim. Eco I. 42: 55-104.

Erwin, T. L. 1983. Beetles and other insects of tropical forest canopies at Manaus, Brazil, sampled by insecticidal fogging techniques. In S. L. Sutton, T. C. Whitmore, and A. C. Chadwick, eds., Tropical rain forests: Ecology and management. Blackwell, Oxford. Pp. 59-75.

Fisk, F. W. 1982. Abundance and diversity of arboreal Blattaria in moist tropical forest of the Panama Canal area and Costa Rica. Amer. Entomol. Soc., Trans. 108: 479-489.

Hf.ithaus, E. R. 1979. Community structure of Neotropical flower visiting bees and wasps: Diversity and phenology. Ecology 60: 190—202.

Janzen, D. H. 1973. Sweep samples of tropical foliage insects: Effects of seasons, vegetation types, elevation, time of day and insularity. Ecology 54: 687-708.

Janzen, D. H., M. Attaroff, M. Fariñas, S. Reyes, N. Rincón, A. Soler, P. Soriano, and M. Vera. 1976. Changes in the arthropod community along an elevational transect in the Venezuelan Andes. Biotropica 8: 193-203.

Janzen, D. H„ and C. M. Pond. 1975. A comparison, by sweep sampling, of the arthropod fauna of vegetation in Michigan, En-glz d and Costa Rica. Royal Entomol. Soc. London, Trans. 127: 30-50.

Janzen, D. H., and T. W. Schoener 1968. Differences in insect abundance and diversity between wetter and drier sites during a tropical dry season. Ecology 49: 96-110.

Levings, S. C., and D. M. Windsor 1984. Litter moisture content as a determinant of litter arthropod distribution and abundance during the dry season on Barro Colorado Island, Panama. Biotropica 16: 125—131.

Patrick, R. 1966. The Catherwood Foundation

Peruvian Amazon Expedition: Limnological and systematic studies. Monogr. Acad. Nat. Sei. Phil. 14: 1-495.

Penny, N. D., and J. R. Arias. 1982. Insects of an Amazon forest. Columbia Univ. Press, New York.

Perry, D. R. 1983. Access methods, observations, pollination biology, bee foraging behavior, and bee community structure within a Neotropical wet forest canopy. Ph.D. diss., Univ. Calif., Los Angeles.

Ricklefs, R. E. 1975. Seasonal occurrence of night-flying insects on Barro Colorado Island, Panama Canal Zone. New York Ento-mol. Soc.,J. 83: 19-32.

Roberts, H. R. 1973. Arboreal Orthoptera in the rain forests of Costa Rica collected with insecticide: A report on the grasshoppers (Acrididae), including new species. Acad. Nat. Sei. Philadelphia Proc. 125: 49-66.

Southwood, T. R. E. 1980. Ecological methods, with particular reference to the study of populations. 2d ed. Chapman & Hall, London.

Stanton, N. L. 1979. Abundance and diversity of Homoptera in the canopy of a tropical forest. Ecol. Entomol. 4: 181-190.

Stout, J., and J. Vendermeer. 1975. Comparison of species richness for stream-inhabiting insects in tropical and mid-latitude streams. Amer. Nat. 109: 263-280.

Tanaka, L. K., and S. K. Tanaka. 1982. Rainfall and seasonal changes in arthropod abundance on a tropical oceanic island. Biotropica 14: 114-123.

Torres, J. A. 1984. Niches and coexistence of ant communities in Puerto Rico: Repeated patterns. Biotropica 16: 284-295.

Wiens, J. A. 1976. Population responses to patchy environments. Ann. Rev. Ecol. Syst. 7: 81-120.

Wolda, H. 1978a. Fluctuations in abundance of tropical insects. Amer. Nat. 112: 1017-1045.

Wolda, H. 1978ft. Seasonal fluctuations in rainfall, food and abundance of tropical insects. J. Anim. Ecol. 47: 369-381.

Wolda, H. 1980. Seasonality of tropical insects. I. Leafhoppers (Homoptera) in Las Cumbres, Panama. J. Anim. Ecol. 49: 277-290.

Wolda, H. 1983. " Long-term" stability of tropical insect populations. Res. Pop. Ecol. Suppl. 3: 112-126.

Wolda, H. 1984. Diversidad de la entomofauna y como medirla. 9th Cong. Latinoamericano Zoo I. (Arequipa), Inf. Final. Pp. 181-186.

Wolda, H„ and R. W. Flowers. 1985. Seasonality and diversity of mayfly adults

(Ephemeroptera) in a "nonseasonal" environment. Biotropica 17: 330-335. Young, A. M. 1982. Population biology of tropical insects. Plenum, New York.

0 0

Post a comment