Daniel P. Wojcik

A Survey for Pathogens of Fire Ants, Solenopsis Spp. in the Southeastern United States

In a survey conducted in the Southeastern United States, one colony in a sample of 1,007 colonies of the red imported fire ant, Solenopsis invicta Buren, was infected with a microsporidium (Protozoa: Microsporida). The normal host of this parasite appears to be the tropical fire ant, Solenopsis geminata (F.). A benign or very mildly pathogenic yeast was associated with 93 (9.24%) of the S. Invicta colonies, and was most common in areas which have been infested with this ant for the longest periods. No pathogens were associated with 83 colonies of the black imported fire ant, Solenopsis richteri Forel. The apparent rarity of bona fide pathogens in imported fire ants in the United States is in marked contrast to the abundance of pathogens in these and other Solenopsis spp. In South America. Four species of microsporidia (possibly new genera) were detected in 22 (7.2%), 12 (3.9%), 6 (2.0%), and 4 (1.3%) of 307 colonies of the tropical fire ant, S. Geminata. One colony of this species was infected by a neogregarine (Sporozoa: Neogregarinida). No pathogens were found in a small sample (53 colonies) of the Southern fire ant, Solenopsis xyloni McCook.

Chemical Mimicry in the Myrmecophilous Beetle Myrmecaphodius excavaticollis.

The myrmecophilus beetle Myrmecaphodius excavaticollis (Blanchard) was found to have species-specific cuticular hydrocarbons acquired-from one of its hosts, the ant Solenopsis richteri Forel. Removal from its ant host resulted in loss of the host hydrocarbons, leaving a cuticular pattern innate to the beetle. When beetles were transferred to colonies of three other Solenopsis species, they acquired the specific hydrocarbons associated with each of the new hosts. This passive integration mechanism is coupled with the beetles armored exterior to enable it to cope with multiple aggressive hosts.

EFFECTS OF FIRE ANTS (HYMENOPTERA: FORMICIDAE) ON HATCHING TURTLES AND PREVALENCE OF FIRE ANTS ON SEA TURTLE NESTING BEACHES IN FLORIDA

Red imported fire ants (Solenopsis invicta Buren) have increasingly been observed in loggerhead (Caretta caretta L.) and green (Chelonia mydas L.) sea turtle nests in Florida, and in the nests of freshwater turtles. They may be attracted to the disturbance, mucous and moisture associated with turtle nesting and establish foraging tunnels into turtle nests shortly after egg-laying, thus increasing the vulnerability of hatchlings to fire ant predation. We conducted experiments on a freshwater turtle (Pseudemys nelsoni Carr) to determine the potential impacts of S. invicta on turtle hatchlings. Over 70% of hatchlings were killed by S. invicta during pipping or shortly after hatching. To determine the extent of S. invicta infestation of sea turtle nesting beaches, we sampled known nesting beaches throughout the state of Florida. Beach surveys indicated that S. invicta are present and often abundant on most beaches and dunes along the Florida coast.

Influence of the proximity and amount of human development and roads on the occurrence of the red imported fire ant in the lower Florida Keys

We examined the influence of both the proximity and extent of human developments and paved roads on the presence of the predatory, non-indigenous, red imported fire ant (Solenopsis invicta). This species was inadvertently introduced into the United States at the port of Mobile, Alabama, around 1930 and rapidly spread to many southeastern states, including Florida. More recently, S. invicta colonized the Florida Keys, an area with a high proportion of rare and endemic vertebrate and invertebrate species. We placed bait transects in transitional salt-marsh, pineland, and hardwood hammocks on 13 of the lower Florida Keys and compared habitat type, the shortest distance of the bait transect to a development or road, and area of development and roads 50, 70, 100, and 150 m around each bait transect for areas with and without red imported fire ants. Red imported fire ants were detected on 21 of the 80 transects and were equally abundant in all habitat types. While all of the development and road variables differed significantly between bait transects with and without red imported fire ants, transects that were closest to roads and that had the largest amount of development within a 150 m radii had the highest probability of presence of red imported fire ants. Recovery efforts for endangered species in areas invaded by red imported fire ants should include analyses of the cumulative impacts of roads and developments in areas near protected lands.

Mating Behavior of 8 Stored-Product Beetles (Coleoptera: Dermestidae, Tenebrionidae, Cucujidae, and Curculionidae)

Mating behavior and mating position were studied for Anthrenus flavipes LeConte, furniture carpet beetle; Trogoderma glabrum (Herbst); Tribolium castaneum (Herbst); red flour beetle; T. confusum Jacquelin duVal, confused flour beetle; Tenebrio obscurus F., dark mealworm; Oryzaephilus mercator (Fauvel), merchant grain beetle; Cryptolestes pusillus (Schonherr), flat grain beetle; and Sitophilus granarius (L.), granary weevil. Actions of the male vary with the species and include touching the female abdominal tip with the maxillary palpi prior to mounting, tapping the female with the antennae and maxillary palpi, wiping motions with the legs, touching the female with the mandibles, and aedeagal movements. C. pusillus exhibited distinctive postcopulatory behavior.

Behavioral interactions between ants and their parasites.

Ectoparasitic and endoparasitic arthropods of ants include species of Acarina (Antennophoridae, Uropodidae, Macrochelidae), Strepsiptera (Myrecolacidae), Hymenoptera (Formicidae, Diapriidae, Eucharitidae), and Diptera (Phoridae). Variation in the style of ectoparasitism is illustrated by the different lifestages involved and differing effects on the hosts by parasitic ants and eucharitids. Considerable variation in behavior occurs between related genera and species of phorids emphasizing the danger of over-generalization on the relationships of ants and their parasites.

First Observation of Polygyny in Fire Ants,Solenopsis SPP., in South America

Polygyny, the coexistence of two or more egg-laying queens in a single colony of a social insect, occurs in several subfamilies of ants (Wilson 1971). The species of Solenopsis, however, were considered to be monogynous until Banks et al. (1973), and Glancey et al. (1973) observed polygyny in Solenopsis geminata (F.) and Solenopsis invicta Buren, respectively. Subsequently, Summerlin (1976) found a single polygynous colony of Solenopsis xyloni McCook. The existence of a spectrum from monogyny to extreme polygyny in the North American S. invicta population was substantiated by Fletcher et al. (1980). Populations of polygynous S. invicta are now known from Florida, Georgia, Mississippi, Louisiana, Texas (Lofgren and Williams 1984), Alabama, Arkansas, and Oklahoma (Banks and Wojcik unpublished). These populations are spreading, and in some cases are proving to be more difficult to control with pesticides than monogynous populations (Glancey et al. 1987). They are also characterized by increased densities of both ants and mounds (Lofgren and Williams 1984). Thus, polygyny in fire ants is currently a subject of interest and concern. We have not encountered polygynous colonies in our extensive surveys for biological control agents for fire ants in the states of Mato Grosso and Mato Grosso do Sul, Brazil, the presumed homeland of S. invicta (Wojcik 1986). Recently, however, we extended our surveys to Argentina, where we collected colonies of polygynous Solenopsis richteri Forel and Solenopsis quinquecuspis Forel. We were alerted to the possibility that we had encountered polygynous fire ants by the enormous biomass of brood in a colony of S. richteri, which has been separated from the soil by flotation (Banks et al. I98 1). This colony yielded 16 non-physogastric, dealate

Polygyny in hybrid imported fire ants.

The occurrence of polygyny in hybrid fire ants from Mississippi was initially indicated by the clustering behavior of the workers around queens. Polygyny was demonstrated by the rate of oviposition of isolated queens, and dissection of samples of queens for the presence of sperm in the spermatheca. The colonies were identified as S. invicta/S. richteri hybrids by gas chromatograph analyses of venom alkaloids and cuticular hydrocarbons.

Imported Fire Ant Infestation of Soybean Fields in the Southern United States

Moderate to heavy infestations of the imported fire ants (IFA), Solenopsis invicta Buren and S. richteri Forel, have reduced soybean production in the southern United States. In early surveys of crop damage, Wilson & Eads (1949) attributed a loss of about three percent of the soybean crop in three south Alabama counties to the ants. Adams et al. (1976, 1977) reported that 16.8 to 49.1 kg/ha of soybeans in Georgia and North Carolina were not harvested because of physical interference of S. invieta mounds with combine operation. Subsequent studies in Florida and Mississippi showed that IFA feeding on the germinating seed reduced the plant stand with an ultimate reduction of up to 600 kg/ha in soybean yield (Lofgren and Adams 1981, Adams et al. 1983). Apperson & Powell (1983) found that increased numbers of IFA correlated positively with reduced soybean yield in North Carolina. These reports of damage to soybeans prompted us to conduct a survey in October 1985 to determine the abundance of IFA in soybean fields and hence, the potential for reduction in soybean yields in the infested areas of the southern United States. A total of 74 fields, from which soybeans had been harvested within the previous 30 days, were inspected in 37 counties in six states. Two fields, separated by a minimum eight km, were chosen at random in each county and the number of active IFA mounds on ten rectangular 0.0405 ha plots in each field was counted. The plots were located at random in each field, but were a minimum 15 m from each other and 30 m from any edge of the field. The plots, which covered three adjacent rows from outside middle to outside middle and varied in length and width according to row spacing, were measured with a calibrated wheel. All mounds were opened with a shovel and examined for ant activity and the presence of brood. The number for the five plots was extrapolated to mounds per ha. The infestation levels (Table 1) ranged from 22.2 to 207.5 active mounds per ha; 87.2% of the mounds were rated as eight or higher by the rating system of Harlan et

A Simple Inexpensive Pitfall Trap for Collecting Arthropods

An easily constructed pitfall trap was made from a large cylindrical plastic container with a snap-on lid, a disposable aluminum pie plate, and heavy-duty aluminum foil. The trap is suitable for collecting with alcohol or volatile killing agents.