Number Of Alates Research Articles

Are LED lights driving the massive nuptial flight swarm of the tramp ant Technomyrmex albipes?

AbstractWhereas most economic and ecological impacts of tramp ant species stem in large part from numerical dominance and exacerbated aggressiveness of workers, those imposed by alate (winged) ants have been rarely described. In the present study, we report an unprecedented massive alate swarming (i.e., mating flight) event in southern Taiwan by a tramp ant species, Technomyrmex albipes (Smith) (Hymenoptera: Formicidae), that triggers immediate pest management responses, and examine factor(s) that potentially contribute to the remarkably high number of alates. We monitored the seasonal activities of T. albipes workers and phenology of alate swarming, attempting to link the worker foraging dynamics with swarm ontogeny. As it was argued that recent streetlight fixtures converted from high‐pressure sodium to light‐emitting diode (LED) may serve as a major cause of the massive swarming, alates' light color preference was investigated. Sex ratio of trapped alates was also assessed to test whether sex‐specific light preference exists in T. albipes. We showed that foraging intensity of workers increased in the spring, peaked in May, and was followed by the nuptial flight season that began in August and lasted for 4 months. The phenological pattern is consistent with the colony dynamics in many other ant species. Although the two light preference experiments did not yield the same results, T. albipes alates overall preferred lights with shorter wavelengths in the active trapping, partially supporting the argument of white LED streetlights contributing to the massive flight. The sex ratio of trapped alates was overall female‐biased, suggesting female alates are disproportionally produced and/or more sensitive toward lights.

Resistance and tolerance of ten carrot cultivars to the hawthorn-carrot aphid, Dysaphis crataegi Kalt., in Poland.

Damage caused to cultivated carrots by the hawthorn-carrot aphid, Dysaphis crataegi Kalt. (Hemiptera: Aphididae) is one of the factors limiting carrot production in Poland. Planting resistant and tolerant cultivars could reduce yield losses due to the damage caused by this pest. This study was conducted to evaluate the resistance and/or tolerance of 10 carrot genotypes to hawthorn-carrot aphid. Their field resistance was determined under field conditions based on five indicators, namely, mean number of alates (migrants) per plant and mean percentage of plants colonized by them, mean seasonal number of aphids per plant, mean number of aphids per plant and mean percentage of infested plants at peak abundance. Antibiosis experiments were conducted under laboratory conditions and pre-reproductive, reproductive time, fertility, and demographic parameters, represented by the net reproduction rate (Ro), intrinsic rate of increase (rm) and mean generation time (T), were calculated. Five cultivars, Afro F1, Nipomo F1, Samba F1, White Satin F1, and Yellowstone showed field resistance. Antibiosis experiments revealed significant differences among the carrot cultivars in the length of the reproductive period, female fecundity in the time equal to the pre-reproduction time, and total progeny of hawthorn-carrot aphid. The intrinsic rate of natural increase (rm) for apterous aphids varied significantly, ranging between 0.181 (Nipomo F1) and 0.343 females/female/day (White Satin F1). Additionally, the estimated net reproductive rate (R0) was the lowest on Nipomo F1, and this genotype was determined to be resistant. Our results suggest that a very high density of trichomes on the leaf petioles (71.94 trichomes/cm2) could adversely affect the feeding, bionomy, and demographic parameters of hawthorn-carrot aphid on the cultivar Nipomo F1. In addition, Napa F1 and Kongo F1 demonstrated high tolerance. Considering all the results collectively, four genotypes, Afro F1, Kongo F1, Napa F1 and Nipomo F1, were relatively resistant/tolerant to the hawthorn-carrot aphid.

A Survey of the Ant Fauna and Seasonal Alate Nuptial Flights at Two Locations in South-Central Texas

Alate ants captured in a Johnson-Taylor suction trap at two locations in South-Central Texas from March 1979 to August 1980 were preserved, counted, and identified to species and sex. At the College Station site, 24 species/morphospecies were identified, with three species being new Brazos County records; at the Ellis Prison Unit, 22 species/morphospecies were identified, with seven new Walker County records. Monomorium talbotae DuBois was collected from both counties and had not been previously reported from Texas. At the College Station site, the number of species/morphospecies and total number of alates collected were greatest in early to late summer. While peak alate nuptial flights coincided with warm temperatures during the late spring and summer months, rainfall seemed to have a less direct effect on the timing of nuptial flights.

The scaling of growth, reproduction and defense in colonies of Amazonian Termites

Phenotypes can evolve through life-history tradeoffs. Termites have been the first eusocial insects on Earth, prompting life history evolution at the colony level. Despite this, termite life-history allocation strategies are poorly known. Here, we addressed this issue using novel data on three common species from the diverse, yet understudied Amazonian termite fauna: Neocapritermes braziliensis, Labiotermes labralis and Anoplotermes banksi. Using Oster and Wilson’s optimal caste ratio theory and Higashi et al.’s termite caste allocation theory as frameworks, we assessed how termite colonies should invest in growth (immatures), reproduction (alates) and defense (soldiers) as they accumulate workers. We also examined whether soldier loss in soil-feeding Apicotermitinae (A. banksi) may have affected allocation strategies. We found that: (1) the scaling of immature number was isometric in the three species, contrary to the leveling off expected under resource limitation; (2) colonies of all sizes were equally likely to produce any number of alates, rather than having a size threshold for reproduction; (3) the scaling of soldier number was unrelated to alate production, but varied from isometry in N. braziliensis to negative allometry in L. labralis despite their similar defense strategies; (4) A. banksi had more immatures per worker and a higher maximum alate number per worker than the other species, suggesting that soldier loss may have allowed higher relative investment in colony growth and, possibly, reproduction. Termites can provide novel insights into life-history allocation strategies and their relation to social evolution, and should be better incorporated into sociobiological theory.

Comparisons Between Alate Aphids Caught in Υellow Water Traps and Aphid Populations on Tomato Plants

Aphid monitoring was conducted by means of yellow Moericke water traps placed in tomato fields in two different localities in Co Boiotia during the growing seasons in 1992 and 1993. Additionally, aphid population densities were estimated by plant sampling. Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer) were the only species which developed populations on plants. Regression analysis between the number of alates from traps with either the number of alates or the total aphid population on plants showed that there was no correlation in the case of M. persicae for both localities and years. However, there were significant relationships between the number of alates in traps and either the number of alates on plants (r2=0.83) or the total aphid population on plants (r2=0.69) for M. euphorbiae in 1992. In 1993, such significant relationships were not found for the latter species, most probably due to extremely low trap catches. Significant relationships were also found between alates in traps, during their immigration period, with either alates on plants (r2=0.93) or the total population on plants (r2=0.80) in M. euphorbiae in 1992.

Simulating the Spread of an Invasive Termite in an Urban Environment Using a Stochastic Individual-Based Model

Invasive termites are destructive insect pests that cause billions of dollars in property damage every year. Termite species can be transported overseas by maritime vessels. However, only if the climatic conditions are suitable will the introduced species flourish. Models predicting the areas of infestation following initial introduction of an invasive species could help regulatory agencies develop successful early detection, quarantine, or eradication efforts. At present, no model has been developed to estimate the geographic spread of a termite infestation from a set of surveyed locations. In the current study, we used actual field data as a starting point, and relevant information on termite species to develop a spatially-explicit stochastic individual-based simulation to predict areas potentially infested by an invasive termite, Nasutitermes corniger (Motschulsky), in Dania Beach, FL. The Monte Carlo technique is used to assess outcome uncertainty. A set of model realizations describing potential areas of infestation were considered in a sensitivity analysis, which showed that the model results had greatest sensitivity to number of alates released from nest, alate survival, maximum pheromone attraction distance between heterosexual pairs, and mean flight distance. Results showed that the areas predicted as infested in all simulation runs of a baseline model cover the spatial extent of all locations recently discovered. The model presented in this study could be applied to any invasive termite species after proper calibration of parameters. The simulation herein can be used by regulatory authorities to define most probable quarantine and survey zones.

Dispersal flight and colony development in the fungus-growing termites Pseudacanthotermes spiniger and P. militaris

Pseudacanthotermes spiniger and P. militaris are two African fungus-growing termites (Termitidae, Macrotermitinae) which may become pests in disturbed agrosystems where they often live in sympatry. To study their development and their reproductive strategies, colonies of both species were reared in the laboratory for 20 and 17 years, respectively, after their foundation from reproductive pairs. The first steps of development were in great part similar in both species, although P. spiniger favoured the defence during the juvenile period, while P. militaris tended to favour a rapid development. While P. spiniger colonies did not produce alates until year 7 of colony life, P. militaris colonies were able to produce a fertile progeny 4 years after their foundation. In contrast, major soldiers were more rapidly differentiated in the incipient colonies of P. spiniger. Dispersal flights occurred every year for 10 years in P. spiniger. In P. militaris, dispersal flights did not occur regularly although alates appeared yearly. The annual number of alates produced by P. spiniger increased with the colony age to reach a maximum of 25,000 individuals and global production of alates was estimated at ca. 150,000 individuals in the life of a colony. The longevity of P. spiniger and P. militaris colonies was around 20 years. These species were shown to be reproductively isolated by multiple pre-mating mechanisms. While chronological differences in dispersal flights contribute to reproductive isolation of the two species, the non-viability of experimental hybrid colonies also indicates the involvement of post-mating mechanisms of isolation.

Two‐year oscillation cycle in abundance of soybean aphid in Indiana

The present study evaluated the population dynamics of the heteroecious soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) during an 8‐year period in Indiana, shortly after its detection in North America. Sampling conducted at multiple locations revealed that A. glycines exhibited a 2‐year oscillation cycle that repeated itself four times between 2001 and 2008: years of low aphid abundance were consistently followed by years of high aphid abundance. Similar patterns of abundance of A. glycines and coccinellids (Coleoptera: Coccinellidae) in soybean fields, both within and between‐years, suggest that late season predation by coccinellids plays a role in the oscillatory cycle of aphids. Insidious flower bugs Orius insidiosus (Say) (Hemiptera: Anthocoridae) were numerically more abundant than coccinellids, although the lack of synchrony between aphids and predatory bugs suggests that O. insidiosus has a limited influence on between‐year variations in aphid density. The inverse relationship between aphid densities before and after the start of the autumn migratory period changes direction in alternate years. High aphid density on soybean in the summer is associated with a reduced number of alate migrants produced in the autumn. Conversely, years with low density aphids on soybean in the summer are characterized by high numbers of alates that migrate to the primary host in the autumn. From a pest management perspective, the 2‐year oscillation cycle of A. glycines is a desirable attribute with respect to population dynamics because it implies that aphids cause significant economic damage only in alternate years (as opposed to every year). Cultural practices enhancing the conservation biological control of Coccinellidae may help to preserve the periodicity of aphid infestation and restrict the pest status of A. glycines.

Distribution of Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in Mississippi

An extensive monitoring and survey program in Mississippi was conducted from 2000 to 2004 to investigate the distribution of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Seventy-two towns from 22 counties in southern Mississippi were monitored with a total of 3914 traps that catch alates during the swarming season. In addition, 259 licensed pest management professionals in Mississippi were surveyed to determine the locations of termite infestations treated. The alates of C. formosanus were recovered in 12 counties with light traps, and termite infestations were documented in an additional 13 from data collected in the termite survey. Infestations of C. formosanus have been documented in urban, urban cluster, rural, and forested areas of Mississippi. However, the distribution in mean total capture of alates for 4 yr differed significantly among the four ecological areas with the highest percentage in forested areas (31%) and the lowest percentage in urban cluster areas (17%). Most of the infestations of C. formosanus were geographically distributed along the coastal areas of southern Mississippi from Gulfport to Pascagoula. The greatest total number of alates captured in light traps was documented in Pearl River County. Mass swarming of C. formosanus occurred primarily in May or June, depending on weather conditions. The number of documented counties with the evidence of large and widely dispersed swarms of C. formosanus in different ecological areas, and the increase in total annual alate captures from 2000 to 2003, suggest that this invasive termite species is now firmly established in Mississippi.

Distribution of Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in Mississippi

An extensive monitoring and survey program in Mississippi was conducted from 2000 to 2004 to investigate the distribution of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Seventy-two towns from 22 counties in southern Mississippi were monitored with a total of 3914 traps that catch alates during the swarming season. In addition, 259 licensed pest management professionals in Mississippi were surveyed to determine the locations of termite infestations treated. The alates of C. formosanus were recovered in 12 counties with light traps, and termite infestations were documented in an additional 13 from data collected in the termite survey. Infestations of C. formosanus have been documented in urban, urban cluster, rural, and forested areas of Mississippi. However, the distribution in mean total capture of alates for 4 yr differed significantly among the four ecological areas with the highest percentage in forested areas (31%) and the lowest percentage in urban cluster areas (17%). Most of the infestations of C. formosanus were geographically distributed along the coastal areas of southern Mississippi from Gulfport to Pascagoula. The greatest total number of alates captured in light traps was documented in Pearl River County. Mass swarming of C. formosanus occurred primarily in May or June, depending on weather conditions. The number of documented counties with the evidence of large and widely dispersed swarms of C. formosanus in different ecological areas, and the increase in total annual alate captures from 2000 to 2003, suggest that this invasive termite species is now firmly established in Mississippi.

Gall surface area is a simple and accurate measure of fitness in Nipponaphidini galling aphids (Homoptera: Aphididae)

We examined the usefulness of five properties of gall size as alternative measures of true gall fitness, defined as the number of alates that emerged from a gall, in four species of Nipponaphidine galling aphids (Neothoracaphis yanonis, Metathoracaphis isensis, Monzenia globuli, and Dinipponaphis autumna). Among five properties (short diameter, long diameter, height, ellipsoidal volume, and ellipsoidal surface area), we determined that surface area was the most accurate and practical measure of gall fitness. This measure is particularly useful for obtaining a sufficient number of gall samples from reared species and species that experience high levels of predation. We also discuss other measures of gall fitness and various problems associated with them.

Interaction of English Grain Aphid, Sitobion avenae (F.) and Their Natural Enemies to an Agro-forestry Environment

The agro-forestry landscape can influence the distribution of wheat-feeding aphids and their natural enemies. Aphid population densities were significantly higher in the arable control areas compared to the arable alleys. The ratio of alate to apterous adults indicated that relatively higher numbers of alates were found in the control areas. The apterous S. avenae adults and nymphs combined were found to constitute approximately 97 % and 98 % of the total from the arable alleys and arable control areas respectively. Parasitism rates (the proportion of aphids that were mummified) were 12.80% and 7.60% in the arable alleys and control areas respectively. In contrast, the numbers of mummies per aphids were found to be lower in the arable controls. The small-scale variation in the distance of plants from the tree rows did not significantly influence insect abundance.

NEW FLIGHT DISTANCE RECORDED FOR COPTOTERMES FORMOSANUS (ISOPTERA: RHINOTERMITIDAE)

The Formosan subterranean termite (FST), Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), was first introduced to New Orleans after World War II inside infested cargo returning from the Orient (La Fage 1987). For the past 60 years, they have spread throughout the New Orleans metro area, displaced native subterranean termite species, and significantly damaged buildings, trees, boats, and railroad ties in the process. To help combat the problem, the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) provided funding for treating buildings in a 50-block area of the French Quarter in New Orleans to determine if an area-wide subterranean termite control program is capable of reducing overall populations. Since 1998, populations have been reduced based on structural inspections, termite activity inside independent monitoring stations installed throughout the French Quarter, and the overall number of alates (winged reproductives) recovered from insect glue boards attached to streetlights throughout the French Quarter (Lax & Osbrink 2003). However, alates are still being captured in significant numbers inside selective areas of the French Quarter and along the borders of this treatment zone. Each year during May and June, untold numbers of male and female alates disperse throughout the area in the early evening and tend to congregate around light sources when present. Information on how far they are capable of flying from a dispersal point was virtually unknown, especially in a large urban area. During field observations in early 2004, it appeared that FST alates were flying across the Mississippi River with the aid of prevailing winds and into the French Quarter. To establish if alates were dispersing into the treatment zone from bordering areas, alates were marked with fluorescent visible powders (Shannon Luminous Materials, Inc., Santa Ana, CA) during two dispersal flights on different evenings at a selected site of known termite activity across the Mississippi River, located directly to the southeast of the French Quarter. In cooperation with USDA-ARS, 445 rectangular (20.7 cm × 10.2 cm) glue boards (TRAPPER® LTD, Bell Laboratories, Inc., Madison, WI) were attached to streetlights along the Riverwalk and throughout the French Quarter to capture potentially marked alates. The glue boards were positioned on the streetlights just below the lantern. Weather conditions, including wind velocity and direction, were recorded each evening with a hand-held weather station (Kestrel® 4000, Nielsen-Kellerman, Boothwyn, PA). Alates were individually marked with a bright orange fluorescent powder with a handheld commercial duster as they were flying in a north to northwest direction over the river. These alates were already in flight at the time of marking and their source could not be located. After marking, every glue board was removed and inspected with a UV black light. New glue boards were used for each dispersal flight event. On 1 June 2004, approximately 50 FST alates were initially marked and a single alate was recovered across the River on a glue board 771 m away (Fig. 1). Then, on 7 June, approximately 50 alates were marked again and two alates were recovered on glue boards 866 m and 892 m away (Fig. 1). The wind direction on 1 and 7 June was from the south and southeast at an average speed of 0.93 m/sec and 0.83 m/sec, respectively. Previously, a wind speed at or below 1.0 m/sec was shown to be one of the most important microenvironmental factors involved in determining dispersal flight activity (Leong et al. 1983).

Distribution and Population Development of Nasonovia ribisnigri (Homoptera: Aphididae) in Iceberg Lettuce

A field study was conducted to determine the distribution and development of aphid Nasonovia ribisnigri (Mosley) (Homoptera: Aphididae) populations in iceberg lettuce, Lactuca sativa L. ‘Salinas’. Lettuce plants were transplanted and caged individually in the field and inoculated with apterous N. ribisnigri at 0, 1, 2, 3, and 4 wk after transplanting in spring and fall 2002. Plants were harvested 15–50 d after inoculations; numbers of alates and apterous N. ribisnigri were counted or estimated on each leaf for each plant. Inoculations during all 5 wk of plant development resulted in successful colonization of lettuce heads. Results indicated that head formation did not reduce the risk of colonization by N. ribisnigri to iceberg lettuce; plants were susceptible to colonization by N. ribisnigri throughout their development. For later inoculations, N. ribisnigri populations were relatively smaller, and aphids were found mostly within the heads. For earlier inoculations, N. ribisnigri populations were larger, and within-plant distributions shifted toward frame leaves. The shift of population distributions toward frame leaves correlated significantly with increases in N. ribisnigri population density. For most inoculations, more aphids were present on wrapper leaves than on other leaves. The proportion of alates did not vary significantly with population density. Population development of N. ribisnigri also correlated significantly with heat unit accumulation. Yellow sticky cards were used to monitor alates in each cage. Catches of N. ribisnigri alates on yellow sticky cards were significantly correlated with total numbers of alates as well as with total population sizes on individual lettuce plants.

Distribution and population development of Nasonovia ribisnigri (Homoptera: Aphididae) in iceberg lettuce.

A field study was conducted to determine the distribution and development of aphid Nasonovia ribisnigri (Mosley) (Homoptera: Aphididae) populations in iceberg lettuce, Lactuca sativa L. 'Salinas'. Lettuce plants were transplanted and caged individually in the field and inoculated with apterous N. ribisnigri at 0, 1, 2, 3, and 4 wk after transplanting in spring and fall 2002. Plants were harvested 15-50 d after inoculations; numbers of alates and apterous N. ribisnigri were counted or estimated on each leaf for each plant. Inoculations during all 5 wk of plant development resulted in successful colonization of lettuce heads. Results indicated that head formation did not reduce the risk of colonization by N. ribisnigri to iceberg lettuce; plants were susceptible to colonization by N. ribisnigri throughout their development. For later inoculations, N. ribisnigri populations were relatively smaller, and aphids were found mostly within the heads. For earlier inoculations, N. ribisnigri populations were larger, and within-plant distributions shifted toward frame leaves. The shift of population distributions toward frame leaves correlated significantly with increases in N. ribisnigri population density. For most inoculations, more aphids were present on wrapper leaves than on other leaves. The proportion of alates did not vary significantly with population density. Population development of N ribisnigri also correlated significantly with heat unit accumulation. Yellow sticky cards were used to monitor alates in each cage. Catches of N. ribisnigri alates on yellow sticky cards were significantly correlated with total numbers of alates as well as with total population sizes on individual lettuce plants.

Host selection, development, survival, and reproduction of turnip aphid (Homoptera: Aphididae) on green and red cabbage varieties.

Host selection, development, survival, and reproduction of the turnip aphid, Lipaphis erysimi (Kaltenbach), on selected green and red cabbage varieties, Brassicae oleracea L. variety capitata, were studied in the laboratory. Although numbers of alate L. erysimi on different varieties varied generally, more alate adults and nymphs were observed on green than on red varieties on day 3; whereas, these differences were not so significant on day 15. There were no significant differences in alate adults on all six varieties on day 15. Numbers of nymphs and apterous adults of L. erysimi varied among the varieties. When mean numbers of those aphids on green varieties were compared with those on red varieties, the green varieties had more nymphs and apterous adults than those on the red varieties. Developmental durations of L. erysimi nymphs also varied among all varieties, and the nymphs fed on green varieties developed longer than those fed on red varieties. Adult longevities on these cabbage varieties were not significantly different; whereas, the adult fecundities were. Survival rates of L. erysimi varied greatly among all varieties, but there are no significant differences between the green and red varieties. Factors that might affect aphid host selection, growth, longevity, fecundity, and survivorship were discussed.

Reflective and Black Mulch Increase Yield in Pumpkins Under Virus Disease Pressure

Experiments were conducted over a 4-yr period that examined the effect reflective, black, and no-mulch had on aphid populations, incidence of virus infected pumpkin plants, and yield of pumpkin. Three different planting dates and their effect on viral infection and yield were also investigated. The use of reflective mulches significantly reduced the number of alates landing in these rows compared with black- or no-mulch rows. The reduction in aphid numbers resulted in a reduction in the percent of plants infected with virus. Approximately 10 times more plants were infected with virus in the black and no-mulch plots than in the reflective mulch plots in mid- to late July. However, by the end of August, all treatments had near 100% of plants infected with virus. This delay in viral infection in reflective mulch plots resulted in a 45 and 120% increase in pumpkin yield compared with black mulch and no-mulch plots, respectively. First plantings always had greater yields than later plantings. The interaction between mulch type and planting time was significant. Reflective mulches increased yields overall, but significantly increased yields compared with black or no-mulch in second and third plantings. The use of reflective mulch combined with timely planting is a cost effective way of delaying virus problems and increasing pumpkin yields in midwestern United States.

Unusual Behavior of Polygyne Fire Ant Queens on Nuptial Flights

This study reports previously undescribed behavior of fire ant queens (Solenopsis invicta) on their nuptial flights. We captured large numbers of alate (winged) queens flying at low altitudes in dense swarms that were virtually devoid of males. We assayed the genotypes of these alate queens at the locus Gp-9, which exhibits strong genotype frequency differences between monogyne (single-queen) and polygyne (multiple-queen) populations, and found that almost all of these low-flying queens originated from polygyne colonies. Comparisons of mtDNA haplotype distributions of these queens to those of alates leaving polygyne nests suggest that the flying queens had not dispersed more than a few hundred meters. Moreover, the proportion of flying queens that were mated did not differ significantly from the proportion of reproductive queens that were mated within the same sites. Thus the flight behavior appears to occur subsequent to mating. We suggest that the flying queens are sampling the local environment in order to select a suitable landing site. Such a site would contain established polygyne nests into which the queens may be adopted as new reproductives.

Temperature and plant nutrient effects on the development, survival and reproduction of Cinara sp. nov., an invasive pest of cypress trees in Africa

Abstract Cinara sp. nov., previously identified as Cinara cupressi (Buckton) (Homoptera: Aphididae), is an important alien aphid pest of cypresses and junipers, and invaded Africa in the late 1980s. The work reported here was carried out as part of a larger programme aimed at the classical biological control of the aphid in Africa. Basic life history attributes including life table statistics of the aphid were quantified in order to facilitate the development of efficient aphid culturing methods and essential baseline information necessary for the culturing of potential parasitoid biological agents prior to selection for introduction to Africa. Developmental rates and fecundity were studied under four constant temperatures (10 °C, 15 °C, 20 °C, and 25 °C). The effects of several plant nutrients (nitrogen, potassium and phosphorus) supplied at different dose levels on life history attributes of Cinara sp. nov. were also studied.Unlike most other aphids, the apterous morph of Cinara sp. nov. developed through only three instars, and the alate four instars. The aphid is highly aggregative and exploits a wide range of feeding sites from young green branches to woody stems. The developmental period of Cinara sp. nov. ranged from 9.3 days at 25 °C to 22.3 days at 10 °C and the developmental threshold was 0.61 °C. Reproduction was delayed, because of the longer duration of development, and nymph production decreased with decreasing temperature. The intrinsic rate of increase ranged between 0.117 at 25 °C and 0.060 at 10 °C. Aphid size increased significantly as temperature was lowered. Wing formation was not induced when apterae were reared for up to three generations at each constant temperature but continuous crowding in the supply cultures held at 21 °C resulted in a high number of alates being formed. No appreciable effects of the different plant nutrients, supplied either singly or in combination, on the duration of instars or overall survival could be detected.

Reproductive success of Macrotermes bellicosus (Isoptera, Macrotermitinae) in two neighbouring habitats.

The fungus-cultivating, mound-building termite Macrotermes bellicosus can reach high densities in African savannah habitats, whereas in forests it is comparatively rare and is only found in relatively open areas. Earlier studies in the Comoé National Park (Côte d'Ivoire, West Africa) suggested that this might be because ambient temperatures are lower in the forest than the savannah. Therefore, forests seem to be suboptimal habitats. During 3 consecutive years we measured relevant fitness parameters in both habitats to test this hypothesis. Colonies in the savannah had higher reproductive outputs. They reproduced annually, producing high numbers of offspring (alates), whereas forest colonies reproduced on average only once every 3 years and even then only low numbers of alates were produced. Annual growth of mound height, which can be regarded as an indicator of colony growth, varied considerably between individual colonies and years. Nevertheless, in two years the growth rate of mounds in the shrub savannah was higher than that of mounds in the gallery forest. Unexpectedly, survival probability as calculated by Kaplan Meier analysis was much lower for colonies in the shrub savannah than for colonies in the gallery forest. Using these data in a computer simulation we calculated lifetime reproductive success (LRS) for an average colony in both habitats. As LRS was much higher for colonies in the shrub savannah than in the gallery forest, these results confirmed our suggestion that the forest is a suboptimal habitat for M. bellicosus.