B. Michael Glancey

Filtration of microparticles from liquids ingested by the red imported fire antSolenopsis invicta Buren

SummaryThe imported fire ant,Solenopsis invicta, has a highly efficient mechanism for filtering particles from food material. Latex microspheres as small as 0.88 μm were filtered and concentrated in the infrabuccal pocket. The compacted mass was then ejected as a pellet. The maximum size latex spheres swallowed by larvæ were 45.8 μm, which approximately corresponds to the diameter of the larval esophagus. The efficient filtration of particles offers little hope for the success of controlled release insecticide formulations that require ingestion of solid particles.ZusammenfassungDie importierte Fenerameise hat einen besonders wirksamen Mechanismus Fremdpartikelchen die in der Nahrung anwesend sind zu filtrieren. Latex Partikelchen von 0.88 μm Durchmesser wurden im infrabukalen Beutel filtriert und eingeengt. Die kompakte Masse wurde nachher als Kügelchen ausgestossen. Die von den Larven verschluckten Latex Kügelchen hatten einen Durchmesser, der eine Länge von 45.8 μm erreichen Konnte und dem Durchmesser der Speiseröhre der Larven entsprach. Die wirksame Filtrierung der Partikelchen bietet wenig Hoffnung auf Erfolg das Durchlassen der Kontrollierten Insektenvertilgungsmittel zu gestatten, wenn sie in harter Form verabreicht werden müssen.

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.

Behavioral and electrophysiological studies with live larvae and larval rinses of the red imported fire ant,Solenopsis invicta Buren (Hymenoptera: Formicidae)

Behavioral and electrophysiological studies with live intact larvae and larval rinses of the red imported fire ant,Solenopsis invicta Buren, give undeniable evidence of a volatile material associated with the larvae of the ant that is capable of eliciting a response from brood-tending workers. In a Y-tube bioassay, worker ants were attracted equally to an airstream blown over sibling larvae or heterocolonial larvae. Workers were also attracted to a rinse of the larvae in a spot bioassay, aggregated about a piece of surrogate brood in another bioassay, and retrieved surrogate brood treated with the rinse material. A dose-response curve constructed from electroantennograms of workers revealed a receptor response of 1–100 brood equivalents.

SPERMATOZOON COUNTS IN MALES AND INSEMINATED QUEENS OF THE IMPORTED FIRE ANTS, SOLENOPSIS INVICTA AND SOLENOPSIS RICHTERI (HYMENOPTERA: FORMICIDAE)

The Coulter Counter IIA, an automatic particle counter, was a fast, accurate device for counting spermatozoa in fire ants. Queens of Solenopsis invicta, the red imported fire ant (RIFA) had an average 5,669,683 @+ 48,148 spermatozoa in the spermatheca two weeks after mating. RIFA males, ready for a nuptual flight, had an average of 8,761,637 spermatozoa. Males and females of S. richteri, the black imported fire ant, had spermatozoon counts extremely close to those of S. invicta. Spermatozoon counts from field collected physogastric S. invicta queens ranged from 551,594 to 5,634,883. A previous study reported counts (determined by a hemacytometer) of only 377,000 spermatozoa in mated RIFA females. These new figures appear to more accurately reflect the reproductive potential of the fire ant.

Scientific Notes: A Naturally Occurring Teratology in the Red Imported Fire Ant (Hymenoptera: Formicidae)

Two aberrant forms of the red imported fire ant Solenopsis invicta Buren have been reported in the literature. The first was a gyandromorph (an individual having both male and female characteristics) found by Hung (1975) and the second, an intercaste (an individual with characteristics intermediate between a worker and a female alate) by Glancey et al. (1980). We now report the finding of a new morphological form which was apparently caused by environmental factors. In October 1984, some field colonies were collected along State Road 100, about 2 miles south of Starke, Florida. The colonies were separated from the soil using our standard drip technique (Banks et al. 1981) and placed in rearing cells. While we were collecting brood from the cells, we noticed some unusual pupae in one of the colonies. Examination of the pupae revealed that the forms were quite unlike anything we had seen before. The antennae and tarsi of these forms were completely deformed. In a normal pupae (Fig. 1) the antennal scape extends outward at an angle of 450 from the mid-line of the frons, past the insertion of the mandible. The funiculus is bent back at a 450 angle so that the tips of the antennae approach each other. In the deformed pupae (Fig. 1) the scapes were close together and extended along the mid-line of the frons. The funiculus was bent back at an angle of 900 toward the mid-line.