Observations of Intercastes in Solenopsis Invicta Buren

The red imported fire ant, Solenopsis invicta Buren, exhibits classical polymorphism, which is defined as the coexistence of 2 or more functionally different castes of the same sex (Wilson 1971). The 2 basic castes are the worker and the female sexuals

The Defensive Role of Volatile Emission and Extrafloral Nectar Secretion for Lima Bean in Nature

Lima bean (Phaseolus lunatus) features two indirect anti-herbivore defenses—emission of volatile organic compounds (VOCs) and secretion of extrafloral nectar (EFN)—which are both inducible upon herbivore damage. In a previous field study, Lima bean benefited from the simultaneous induction of the two defenses, yet it remained unclear whether both had contributed to plant protection. Our experimental approach aimed at studying the defensive role of both indirect defenses simultaneously. Tendrils were sprayed with jasmonic acid (JA) to induce both defenses, and performance was compared to that of others that were treated with a synthetic blend of either EFN or VOCs. Confirming earlier results, JA treatment and application of the VOC mixture induced EFN secretion in treated tendrils in quantitatively similar amounts. The composition of the applied synthetic blend of EFN was adjusted to match the concentration of EFN secreted from JA- and VOC-treated tendrils. Repeated application of either enhanced the performance of several fitness-relevant plant parameters such as growth rate and flower production. Tendrils treated with JA showed a similar trend, yet some fitness-related parameters responded less to this treatment. This suggests a minor importance of any putative JA-dependent direct defense traits or higher costs of JA-elicited responses as compared to VOCS and EFN, as otherwise JA-treated tendrils should have outperformed VOC- and EFN-treated tendrils. Moreover, the beneficial effect of applying synthetic EFN alone equaled or exceeded that of VOCs and JA. Ants were by far the dominant group among the arthropods that was attracted to JA-, VOC-, or EFN-treated tendrils. The results suggest that EFN plays a more important role as an indirect defense of lima bean than VOCs or any other JA-responsive trait

Areawide Suppression of Fire Ants

The imported fire ants, Solenopsis invicta and S. richteri, were inadvertently introduced into the USA in the early 1900s and currently inhabit over 129 million ha in Puerto Rico and 12 southern states, from Texas to Virginia (Callcott and Collins, 1996; USDA-APHIS map). Imported fire ants have also become established in isolated sites in California, Arizona, New Mexico and Maryland. Strict quarantine procedures have limited the spread of this pest (Lockley and Collins, 1990), but eventually populations will expand westward in increasing numbers in New Mexico, Arizona and California. They will also move upward along the Pacific coast, southward into Mexico and the Caribbean and northward in Oklahoma, Arkansas and Tennessee and along the eastern seaboard into Maryland and possibly Delaware (Korzukhin et al., 2001). Mature monogyne (single queen) fire ant colonies contain 100,000 to 250,000 workers (Tschinkel, 1988, 1993) and reach infestation rates of over 130 mounds/ha. In the last few decades, polygyne fire ant colonies (multi-queen colonies) appear to be proliferating in the southern states. With polygyne populations, the number of mounds may reach over 500/ha (Porter et al., 1991; Porter, 1992), resulting in interconnected super-colonies because of the lack of territoriality among polygyne colonies (Morel et al., 1990; Vinson, 1997). Control is difficult because more queens must be killed. Imported fire ants destroy many ground-inhabiting arthropods and other small animals (Vinson and Greenberg, 1986; Porter and Savignano, 1990;Jusino-Atresino and Phillips, 1994; Wojcik, 1994; Forys et al., 1997; Allen et al., 1998; Williams et al., 2003). Because fire ants are highly aggressive when their nests are disturbed, this often results in painful stings to humans and their pets. Between 30 and 60% of the people in the infested areas are stung each year, with hypersensitivity occurring in 1% or more of those people (deShazo et al., 1990, 1999; deShazo and Williams, 1995), suggesting that over 200,000 persons per year may require medical treatment

Specificity of the Red Imported Fire Ant Phagostimulant Response to Carbohydrates

The red imported fire ant, Solenopsis invicta Buren, is considered an oil-loving feeder, however, carbohydrates are essential ingredients in the diet of the fire ant also. Comprehensive screening of mono-, di-, and tri-saccharides demonstrated that glucose, fructose, fucose, sucrose, maltose, turanose and raffinose were significant phagostimulants for fire ant workers. It was also found that while D-glucose and L-fucose, the naturally occurring isomers, were active, the opposite diastereomers were not. Any structural modification of the glucose molecule resulted in loss of activity. None of the sugar alcohols evaluated were active. The fire ant is an agricultural pest and the many reports of fire ant damage to food crops may be linked to their need for dietary carbohydrates. A knowledge of carbohydrate phagostimulants may help to understand specificity of fire ant/plant interactions

Residual Toxicity of Some Fluoroaliphatic Sulfones to the Red Imported Fire Ant

Thirty-six fluoroaliphatic sulfones were tested to determine their residual toxicity to Solenopsis invicta Buren in soil. Six of the compounds gave \u3e90% kill of the ants after they were exposed for 4 days at 10 ppm. When tested at 1.0 ppm, only one compound, AI3-10841, gave appreciable mortality. This compound was tested at 10 ppm in soil held outdoors under ambient summer conditions. Mortality 8 days following initial exposure to samples of this soil was 100% for 12 weeks and 91 to 100% from 20 to 36 weeks

Spatial representation of alarm pheromone information in a secondary olfactory centre in the ant brain

Pheromones play major roles in intraspecific communication in many animals. Elaborated communication systems in eusocial insects provide excellent materials to study neural mechanisms for social pheromone processing. We previously reported that alarm pheromone information is processed in a specific cluster of glomeruli in the antennal lobe of the ant Camponotus obscuripes. However, representation of alarm pheromone information in a secondary olfactory centre is unknown in any animal. Olfactory information in the antennal lobe is transmitted to secondary olfactory centres, including the lateral horn, by projection neurons (PNs). In this study, we compared distributions of terminal boutons of alarm pheromone-sensitive and -insensitive PNs in the lateral horn of ants. Distributions of their dendrites largely overlapped, but there was a region where boutons of pheromone-sensitive PNs, but not those of pheromone-insensitive PNs, were significantly denser than in the rest of the lateral horn. Moreover, most of a major type of pheromone-sensitive efferent neurons from the lateral horn extended dendritic branches in this region, suggesting specialization of this region for alarm pheromone processing. This study is the first study to demonstrate the presence of specialized areas for the processing of a non-sexual, social pheromone in the secondary olfactory centre in any animal

(±)-des-N-morphinan: a unique bridged hydrocarbon attractant for the rhinoceros beetle, Oryctes rhinoceros; and development of an olfactometer

An olfactometer designed for Oryctes rhinoceros (L.) is described and its effectiveness demonstrated by a comparison of results with field tested chemicals. Using the olfactometer, (±)-Des-N-morphinan, but not its stereoisomer was found to be a strong attractant for adult rhinoceros beetles. This is the 1st synthetic bridged hydrocarbon found to be an insect attractant