Tropical Insects Research Articles

The problem of resistance to insecticides in tropical insect pests

The development of resistance to insecticides in insect pests is an important and increasing problem. As insecticide use increases in tropical areas, the numbers of resistant insect strains will increase. The adverse effects of insecticide resistance include crop losses, increased production costs, increased environmental hazards, and socio-economic problems. The increasing difficulties and costs of discovering and developing new insecticides together with the widespread occurrence of resistant strains of insect pests means that insecticides are a limited resource that must be conserved. Methods of conserving insecticides include sensible management of their use and the implementation of IPM programmes. The problems of insecticide resistance and strategies for minimizing and managing resistance in tropical areas are discussed using examples of insect pests of stored products, cotton, rice and bananas.

Insect biosystematic services in Africa: Current status and future prospects

The recent history of initiatives in support of tropical insect taxonomy and the current status of the insect collection resources of Africa are reviewed with special emphasis on the development of the Department of Entomology, National Museums of Kenya as a regional centre for insect biosystematic services, training and research. Specific proposals are offered for the future development of such centres.

Natural enemies may be a cause of discrete generations in tropical insects

It is commonly believed that the marked seasonally of temperate regions results in the insects that live there often having discrete generations, whereas in the tropics, generations are more likely to overlap because of the more-or-less continuously favourable conditions. These sweeping generalizations, however, are misleading. Several examples are now known of tropical insect populations that tend to show discrete generations, both under equilibrium1–5 (Fig. la) and non-equilibrium conditions6–9, which are not seasonally determined. We are also struck by the frequency with which laboratory insect populations cultured under constant conditions show discrete generations10–12 (Fig. 1b). A common factor in these examples is the presence of insect parasitoids as a major mortality factor. Here we demonstrate, using theoretical population models, one way in which parasitism can be the cause of approximately discrete generations. In particular, we show that the ratio of the lengths of the host and parasitoid life cycles is of prime importance in determining whether generations tend to be discrete or continuous and discuss the importance of this in biological control.

Altitude, habitat and tropical insect diversity

Sample size and species richness of a series of light-trap samples taken in a number of localities in the Republic of Panama are given. Species richness as well as sample size decreased gradually with increasing altitude over a 100–2200 m range, in contrast to data from the literature which demonstrated a maximum at intermediate elevations. It is suggested that differences in technique, especially the continuous nature of the sampling in the present case are responsible for this discrepancy. Moderate human disturbance, which leaves a relatively high tree species diversity in the area has a surprisingly little, if any, effect on insect diversity. A large perturbation of the environment does, however, decrease species richness of the insect fauna.

Reproductive Seasonality in the Tropical Genus Eurema (Lepidoptera: Pieridae)

Reproductive Seasonality in the Tropical Genus Eurema (Lepidoptera: Pieridae)

Dormancy in tropical insects.

Diapause is frequently viewed as a developmental strategy unique to insects of the temperate zone. My primary objective in this review is to dispell this myth by presenting evidence for the widespread existence of diapause among tropical species. Although the environmental regulators are still poorly defined, I attempt to identify factors implicated in regulation and some of the special problems of diapause in the tropics. For purposes of this review I restrict my discussion to insects living within 200 of the equator, but clearly this is an arbitrary line. Winter in temperate zones presents a conspicuous obstacle, and a wealth of studies examine diapause as an adaptation to circumvent this inimical period. Reviews have focused on diapause physiology (72), endocrinology (19,31, 129), ecology (22, 24, 25, 115, 116), genetics (55), evolution (12, 33), thermoperiodism (6), clock mechanisms (5, 102), and cold tolerance (37, 101). Masaki's review on summer diapause (76) is especially relevant to this review because the warm summer of the temperate zone is much akin to the tropical environment. Although there are many definitions of diapause, I use the term to refer to an arrest in development that occurs at a specific stage. Egg, larval, pupal, and adult diapauses are all well documented, but for most species diapause can be expressed in only one stage of the life cycle. Diapause is programmed far in advance of the actual developmental arrest and thus differs from a simple quiescence that is an immediate response to adverse conditions. For some tropical species the information available is too sketchy to allow adequate

Dormancy in Tropical Insects

Dormancy in Tropical Insects

Perching Heights and Nocturnal Communal Roosts of Some Tiger Beetles (Coleoptera: Cicindelidae) in Southeastern Peru

When disturbed, diurnally active species of tiger beetles flew from the forest floor, where they foraged, to temporary perches in the vegetation. The height of these perches was correlated with the size of the species. At night, these species roosted for 10-12 hours at the same height as their temporary daytime perches. Some species congregated nocturnally on communal roosts of 2-9 individuals during the early rainy season. Species from sandy edges of rivers roosted on grass blades at night. When 10 individuals were removed one at a time from the grass and placed on the ground, four were captured and ingested within two minutes by large nocturnally-active tiger beetles. ROOSTING AND PERCHING BEHAVIOR in insects is a readily observed and quantifiable pattern in tropical forest habitats. This paper presents data from observations of tiger beetles (Coleoptera: Cicindelidae) in south-eastern Peru that can be compared to patterns of perching behavior and nocturnal roosting behavior described for other groups of tropical forest insects. For instance, perch height is correlated with body size for tropical scarabaeid beetles (Howden and Nealis 1978); this pattern has been attributed to searching behavior for a limiting resource (Peck and Forsyth 1982). Nocturnal roosts, often communal, of butterflies have been attributed to thermoregulation and protection from physical factors (Young 1979) as well as predation (Young and Thomason 1975; Turner

Population Biology of Tropical Insects

Population Biology of Tropical Insects

Population Biology of Tropical Insects.

Population Biology of Tropical Insects.

Reanalysis of Caswell's Neutral Models

In an important and much quoted paper Caswell (1976) derived models of community structure (the numbers of individuals and species) that did not involve biological interactions. From these neutral models he contended that biological interactions depress values of the Shannon-Wiener diversity index below model predictions in tropical bird, insect, and tree communities and that values equal to predictions obtain for temperate birds and forest trees. Caswell's conclusion was that biological interactions lead to less diverse communities than neutral-model predictions, and diversity is depressed more where abiotic factors have only slight influence on biological interactions. Such conclusions are in marked contrast to the traditional views that high diversity in particular is generated by biological interactions. Using Caswell's neutral model other workers have also found that diversity is less than neutral-model predictions in, e.g., marine benthic communities (Rainer 1981). (An example purporting to support the traditional view [Gray 1978] was shown by Rainer to be due to the use of an incorrect logarithm base, and this data set also supported Caswell's contention.) It seemed to us improbable that all examples should consistently be equal to or below neutral-model predictions, and this led us to reexamine Caswell's model. In most communities species are patchily distributed, and the total abundance of a species is the sum of the abundances in all patches. Because of the multiplicity of factors that influence any given species, the distribution of species within any patch will be rather unpredictable. A species having been eliminated from a patch may recolonize by migrating from other patches. Thus, extinction over ecological time is generally a local phenomenon. The two species-abundance distributions that have been shown to fit a large number of different assemblages are the logseries distribution and the lognormal distribution. Frequently it is impossible to determine which of these two distributions is more apt, since they both give excellent fits to the data. In a survey of stochastic models of population growth, Kendall (1948) pointed out that the success of fitting the logseries to entomological data implies that the density of the abundances must be in the form

Population Biology of Tropical Insects. Allen M. Young

Previous articleNext article No AccessNew Biological BooksPopulation Biology of Tropical Insects. Allen M. Young Donald R. Strong, Jr.Donald R. Strong, Jr. Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 58, Number 2Jun., 1983 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/413292 Views: 1Total views on this site Copyright 1983 Stony Brook Foundation, Inc.PDF download Crossref reports no articles citing this article.

Dietary water balance in a tropical insect

Dietary water intake of the tropical grasshopperPoecilocerus pictus fedad libitum from hatching to death on the milkweedCalotropis gigantea averaged 85 or 51 g at 26°C and 171 or 78 g at 36°C for a female and male respectively. As much as 54 or 96 g dietary water is lost via faeces by a female at 26 or 36°C; the corresponding values for a male was 37.5 and 36.2 g. A male or female carried at death about 9 or 6% of the respective dietary water absorbed at 26 or 36.°C. Water loss via exuvia amounted to 26 mg in all the series. Due to oviposition 4.8 or 7.4% of the total water absorbed was lost by a female at 26 or 36°C. There exist a very close relationship between the efficiencies of matter assimilation and water absorption. The high dietary water intake and absorption rates reported for the tropical lepidopteranDanaus chrysippus are correlated with the accumulation of water to meet the requirements during the nonfeeding pupal stage.

Fables and Foibles

Fables and Foibles Sylvia M. Vardell (bio) and Nancy A. Burris (bio) Editor's Note: Fables is a short story with a long history; included in it are the titles of all the winners of the Caldecott Medal. Once a mouse and the biggest bear you've ever seen found themselves keeping company on the little island of Ashantitozulu. African traditions suggest their friendship descends from the crowded days of Noah's Ark, but the animals of the Bible seem to have always room for one more among them. One fine day, just as the rooster crows, this mouse and bear, being much bothered by the tropical insect population, set out to find out why mosquitoes buzz in people's ears. A tree is nice for resting under, but the bugs this season were relentless. Fortunately, Madeline, the mouse, and Sylvester, the bear, didn't have to travel many moons before they met up with an oxcart man, named Sam Bangs, and Moonshine, his feline companion. That cat took an interest in the mouse and Sylvester had to effect Madeline's rescue. Sam told our animal friends about the little house where the girl who loved wild horses lived. "She knows about the song of the swallows, where the wild things are, and how to play Jumanji," he confided. He claimed that if they were strong and good, the fool of the world and the flying ship would agree to take them to her. Madeline and Sylvester were skeptical of this Cinderella plan. Instead, they thanked him and continued on their way. Once Madeline had to make way for ducklings in their path or risk being stampeded. Sylvester spotted a pretty red rock. "Finders keepers," he thought to himself. Our friends were now getting discouraged. They decided to split up and meet again nine days to Christmas at the egg tree. Sylvester (and the magic pebble) followed an arrow to the Sunday Revival. For Madeline, it was a time of wonder. The big snow had come to the northern part of the island and there was white snow, bright snow everywhere. The snowy day forced her to seek shelter with the funny little woman of Dru Mmerh Off who, in return, demanded to be told a story. "A story?" queried Madeline. She hesitated, then began, "Once a strange trio, including the chanticleer, and the fox, and the frog, went a-courtin' a sweet young pigeon. . ." Meanwhile, Sylvester was running into problems of his own. A tall, robed figure mounted the pulpit and began to preach about the old man of Baboushka, and the three kings of Duffy, and the devil himself! The preacher said a silent prayer for a child who trembled near the front. Sylvester continued on his solitary journey. He met a nightingale, Mei Li, whose lovely song promised to take him home. "May I bring a friend?" he asked, thinking of Madeline. As soon as he did, Madeline appeared beside him, and, in the next breath, our heroes found themselves resting on the moss under the old tree. (Remember the magic red rock?) Winter had discouraged those buzzing mosquitoes, and all in all, our worldly bear and mouse friends were quite content to stay put. Abraham Lincoln couldn't tell you a truer tale! Sylvia M. Vardell and Nancy A. Burris Sylvia M. Vardell and Nancy A. Burris both teach at the University of Houston, Victoria. Bibliography and Sequential Answer Key Fables. Arnold Lobel. Harper, 1981. Google Scholar Once a Mouse. Marcia Brown. Scribner's, 1962. Google Scholar The Biggest Bear. Lynd Ward. Houghton, 1953. Google Scholar The Little Island. Golden MacDonald. Ill. Leonard Weisgard. Doubleday, 1947. Google Scholar Ashanti to Zulu: African Traditions. Margaret Musgrove. Ill. Leo and Diane Dillon. Dial, 1977. Google Scholar Noah's Ark. Peter Spier. Doubleday, 1978. Google Scholar Animals of the Bible. Helen Dean Fish. Ill. Dorothy P. Lathrop. Lippincott, 1938. Google Scholar Always Room for One More. Sorche Nic Leodhas. Ill. Nonny Hogrogian. Holt, 1966. Google Scholar One Fine Day. Nonny Hogrogian. Macmillan, 1972. Google Scholar The Rooster Crows. Ill. Maud and Miska Petersham. Macmillan, 1946 (traditional Mother Goose). Google Scholar Why Mosquitoes Buzz in People's Ears. Retold by...

New Titles

New Titles

“Long‐term” stability of tropical insect populations

SummaryFluctuation patterns of insect species in the humid tropics are compared with those from the temperate zone, using data on species abundance covering a period of at least 6 years. The stability of a set of species is characterized by a Stability Index, which is, basically, the mean of the variances of the abundances of these species. Data on Homoptera, Dictyoptera, Orthoptera and mosquitos from the Panama Canal Area are compared with information from Europe, Australia and Japan. It is concluded that these tropical insects, even the ones from a relatively undisturbed tropical forest, are just as variable, or stable, as these temperate ones. Some exceptional temperate haibtats, such as the Schreierbach in Austria, seem to be much more stable than any known tropical ones.

An evolutionary-ecological model of the evolution of migratory behavior in the Monarch Butterfly, and its absence in the Queen Butterfly

This paper presents a model that generates testable hypotheses concerning the evolution of long-range migratory behavior in the Monarch Butterfly,Danaus plexippus and the general absence of such behavior in a related form, the Queen,D. gilippus (Lepidoptera: Nymphalidae: Danainae). An attempt is made to reconstruct a probable transition within the Neotropical forest-dwelling danaines associated with woody Asclepiadaceae (and to a lesser extent, perhaps some Apocyanaceae) as larval food plants to a progenitor stock of the Monarch and Queen in more seasonal tropical regions, and eventually temperate regions, and associated with herbaceous asclepiads such asAsclepias. A basic premise of the proposed hypothetical model is that the colonization of secondary habitats in seasonal tropical regions of Central America preadapted both forms to an eventual colonization of the sub-temperate and temperate zone of North America. The assumed evolutionary diversification of the herbaceousAsclepias species in North America provided an evolutionary stepping stone for the expansion of these danaines into this region. Owing to strong selection arising from the co-association of the Monarch and Queen with the same species ofAsclepias in the subtropical region of North America, eventually there was selection for the colonization of the higher latitudes by the Monarch, whereAsclepias thrived. Being essentially a tropical insect, the Monarch evolved an obligatory long-range migratory behavior to allow colonization of the temperate zone annually, and necessitating the use of overwintering sites in Mexico and other places.

Harmonious Coexistence of Hispine Beetles on Heliconia In Experimental and Natural Communities

Hispine beetles that live as adults in the rolled leaves of Heliconia plants are prime suspects for interference competition among species, based upon theory developed by vertebrate ecologists. These beetles are tropical, long—lived, and very closely related, eat the same food, and use the same habitat. However, hispines do not conform to this theory: 1) Rolled—leaf hispines are not aggressive intra— or interspecifically, and are not displaced or intimidated by encounters between individuals. 2) Adults are not segregated by species into different leaf subsets of host populations. Species mingle together in patterns that do not suggest interspecific competition. 3) Number of species does not affect interspecific association. 4) Pairwise correlations indicate that only one beetle (Cephaloleia) of the 13 species studied is even weakly segregated from others. It prefers leaves on younger plants than those preferred by other species, and its segregation is a result of subtle habitat differences rather than competition. 5) Interspecific segregation among hispanies does not increase with density in leaves. 6) No higher order interactions were detected in species associations. 7) Experiments showed that habitat heterogeneity does not measurably influence interspecific association in hispine communities as delimited by a single host species. Experimental communities in nature were constructed with minimal habitat heterogeneity, and no mor segregation or aggregation between hispine species occurred in experimental than in natural communities. Additional observations suggest that levels of food and habitat are commonly not limiting to hispine populations, which suffer heavy parasitism and predation. I infer that community structure of hispines on Heliconia is affected greatly by natural enemines. Heliconia is not chemically noxious to hispines, and experiments show that hispines grow at maximum rates on the relatively low nitrogen content of Heliconia. Theories of community structure based upon interspecific competition, and those based upon allelochemical protection of host plants against adapted insects, are not suitable for hispine communities on Heliconia. My conclusions largely agree with those of Hairston et al. 1960. Additional work with parasitism, predation and other factors that may affect hispine populations, such as the weather, migration, and spacing of host plants, is necessary to establish key and regulatory factors for these tropical insects.

Neotropical Heliconia Insect Communities

The insect fauna associated with Heliconia plants is one of the most extensively studied of all (non-cultivated) Neotropical insect-plant associations. Studies on Heliconia insect communities have centered on either the herbivorous insects that feed on young rolled leaves, or on those insects that live inside the water-filled floral bracts. I hypothesize that Heliconia floral morphology, in which flowers are protected in water-filled, cuplike bracts, evolved as a defense against flower-feeding and seed-eating insects. This small body of water has, however, attracted a varety of aquatic insects which are Heliconia-specific. Much of the research on Heliconia insect communities sheds light on more general hypotheses concerning the ecology and evolution of tropical insect communities. Heliconia research has pointed out the importance of plant biochemistry, plant phenology, and local plant distributions in determining the life history patterns, species diversity, and population densities of obligate insect associates. Studies on the leaf-feeding herbivores and the bract inhabitants indicate that neither intraspecific nor interspecific competition is a major structuring element in these communities. Parasitism, facilitation, and habitat age are more important than competition in structuring these insect communities. A clear succession can be followed among the insects in the Heliconia bracts. Insect species that are better adapted to water low in detritus are found in the youngest bracts, whereas insect species that use, or are tolerant of, high levels of detritus are found as the bracts age. Finally, biogeographyc patterns show that local accumulations of insect species in Heliconia inflorescences follow a power function similar to that which is used to describe the accumulation of species on islands. On a larger scale, moisture and number of Heliconia species in any location seem to be important in determining species richness among leaf-feeding insects, whereas floral morphology, bract size, and geographic location are important in determining the species composition of the insect communities in Heliconia inflorescences.

A new method for censusing animal populations: The number of Eciton burchelli army ant colonies on Barro Colorado Island, Panama

A new technique for estimating the size of an animal population is described. This technique is used to provide an up to date estimate of the number of colonies of the army ant Eciton burchelli on Barro Colorado Island, Panama. There have been approximately 50 colonies of this species on Barro Colorado Island for more than thirty years. The relative constancy of this population is contrasted with the great temporal variability of other tropical insect populations.