The Function of Hitchhiking Behavior in the Leaf‐cutting Ant Atta cephalotes1

In some leaf‐cutting ant species, minim workers ride on the fragments of leaves as they are carried back to the nest from the cutting site. There is convincing evidence that these “hitchhikers” can protect the leaf carriers from attack by phorid (Diptera: Phoridae) parasitoids, but we consider the possibility of other functions for the hitchhiking behavior. It has been hypothesized that the hitchhikers (1) feed on leaf sap from the edges of the cut leaves; (2) ride back to the nest to save energy; (3) get caught on the fragments as they are cut, and hitchhike because they cannot (or will not) get off; and (4) begin the process of preparing the leaf to enter the fungal gardens in the nest, perhaps by removing microbial contaminants. We observed hitchhikers of Atta cephalotes in 14 nests at the La Selva Biological Station in Costa Rica. There was no difference in the proportion of leaf carriers with hitchhikers between day and night. Because the nests we observed were largely nocturnal, more than 90 percent of the hitchhiking occurred at night. The phorid parasitoids are usually considered to be diurnal, so the preponderance of nocturnal hitchhiking suggests other functions in addition to parasitoid defense. Hitchhikers spent more time in the defensive head‐up posture during the day, but spent more time in the head‐down posture at night. The head‐down posture may indicate cleaning or other leaf preparation. The hitchhikers were never observed feeding on sap. Hitchhikers frequently got onto and off of the fragments, and so they were not “marooned.” Few hitchhikers rode all the way back to the nest and were often moving on the leaf fragment; these observations make the energy conservation hypothesis less likely, although we cannot reject it. We conclude that parasitoid defense is an important function of hitchhiking but also that there are probably other functions when parasitoids are absent. Based on available data, the most likely possibility is preparation of the leaf fragment before it enters the nest.     

The effect of four fruit species on the parasitization rate of Anastrepha fraterculus (Diptera: Tephritidae,Trypetinae) by Diachasmimorpha longicaudata (Hymenoptera: Braconidae,Opiinae) under laboratory rearing conditions

In the laboratory, the effect of host fruit species Citrus paradisi, C. aurantium, Prunus persica, and Psidium guajava on A. fraterculus parasitism by Diachasmimorpha longicaudata was studied. The number of ovipositor-probing events and the probing-time were documented to evaluate the role of fruit chemistry, and epicarp and mesocarp thickness, respectively. The relationship between the parasitization rate and fruit size in particular plant species was analyzed by applying a simple regression. Results showed that guava and peach yielded significantly more parasitoids than both Citrus spp. Probably, the parasitization rate of D. longicaudata on A. fraterculus would be influenced in part by chemical and physical factors from fruit species.     

Dispersion patterns of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in citrus orchards in southeast Brazil

We studied the dispersion patterns of the exotic endoparasitoid, Diachasmimorpha longicaudata (Ahsmed) (Hymenoptera: Braconidae), in 1999 (summer) and in 2000 (winter) in a citrus orchard in southeast Brazil. Different population densities of D. longicaudata were released in the centre of the orchard, and their dispersion was determined by using yellow, sticky, rectangular traps, placed in various distances and heights around the release point. Our results suggest that during summer, climatic conditions did not affect dispersion. However, in winter, dispersion rates were positively affected by temperature, and negatively by rainfall. Both estimated dispersal distance and surface were higher in summer than in winter for all release densities. Dispersion peaked at 2000 parasitoids ha^?1 in summer and 8000 parasitoids ha^?1 in winter. The importance of our results for the biological control of fruit flies by augmented or innoculative releases of D. longicaudata in southeast Brazil is discussed.     

Spiroplasma species in the Costa Rican highlands: implications for biogeography and biodiversity

More than 1,000 Spiroplasma isolates have been obtained from horse flies and deer flies (Diptera:Tabanidae) in the United States and Canada. However, the spiroplasma biota of Central America is poorly known. In August of 1995 and 1998, 13 isolates were obtained in 14 attempts from horse flies of a single species, Poeciloderas quadripunctatus, taken in the Costa Rican highlands (1,100–2,000 m). The majority of the “isolates” proved to be mixtures of two or more Spiroplasma species, but after filter cloning, single strains emerged that were designated as representatives of the 13 accessions. Six distinct spiroplasma serogroups were identified from these isolations. Three of the strains are putative new species with no serological relationship to any other Spiroplasma species. A fourth strain is a putative new species that may be distantly related to S. helicoides, a southeastern U.S. species. These four strains are accorded herein status as representatives of new serogroups: strain BARC 4886 (group XXXV); strain BARC 4900 (group XXXVI); strain BARC 4908 (group XXXVII); and GSU5450 (group XXXVIII). A fifth Spiroplasma species was very closely related to S. lineolae, known previously only from the Georgia (U.S.) coast. The sixth was most closely related to subgroup VIII-3, known from Texas and the southeastern U.S. Discovery of six spiroplasma species in only 13 attempted isolations reflects diversity seldom equaled in southeast Georgia, and never elsewhere in the U.S. These results are consistent with a hypothesis that spiroplasma diversity increases from north (Nova Scotia) to south (Georgia and Costa Rica). The discovery of significant affinity between some spiroplasmas of the southeastern U.S. and the Costa Rican highlands was unexpected, but may reflect a climatically complex Pleistocene history.

Factors Affecting Engorgement Behavior in the Salt Marsh Horse Fly, <Emphasis Type="Italic">Tabanus nigrovittatus</Emphasis> Macquart (Diptera: Tabanidae)

Female Tabanus nigrovittatus were field collected and used in laboratory experimentation to explore physiological and behavioral factors that affect engorgement. Previous studies showed sulfakinins act as feeding satiety factors in insects. This study demonstrates that sulfakinins have differing effects on engorgement that is dependent on the feeding technique used in the laboratory. The satiety effect of sulfakinin on flies engorging using the blood-soaked Kimwipe® feeding technique is not in agreement with previous experiments using an alternate feeding technique with artificial membranes. This study is the first to demonstrate that the temperature of blood is a significant factor for engorgement in this species. Also, the percentage of flies engorging is significantly different depending on the feeding technique used.     

Wing morphometrics as a possible tool for the diagnosis of the Ceratitis fasciventris,C. anonae,C. rosa complex (Diptera,Tephritidae)

Previous attempts to resolve the Ceratitis FAR complex (Ceratitis fasciventris, Ceratitis anonae, Ceratitis rosa, Diptera, Tephritidae) showed contrasting results and revealed the occurrence of five microsatellite genotypic clusters (A, F1, F2, R1, R2). In this paper we explore the potential of wing morphometrics for the diagnosis of FAR morphospecies and genotypic clusters. We considered a set of 227 specimens previously morphologically identified and genotyped at 16 microsatellite loci. Seventeen wing landmarks and 6 wing band areas were used for morphometric analyses. Permutational multivariate analysis of variance detected significant differences both across morphospecies and genotypic clusters (for both males and females). Unconstrained and constrained ordinations did not properly resolve groups corresponding to morphospecies or genotypic clusters. However, posterior group membership probabilities (PGMPs) of the Discriminant Analysis of Principal Components (DAPC) allowed the consistent identification of a relevant proportion of specimens (but with performances differing across morphospecies and genotypic clusters). This study suggests that wing morphometrics and PGMPs might represent a possible tool for the diagnosis of species within the FAR complex. Here, we propose a tentative diagnostic method and provide a first reference library of morphometric measures that might be used for the identification of additional and unidentified FAR specimens.     

A revision of the Nearctic species of Liancalus Loew (Diptera,Dolichopodidae)

The genus Liancalus Loew is revised for the Nearctic Region. Seven species are documented from this region including two new species: Liancalus genualis Loew, Liancalus hydrophilus Aldrich, Liancalus limbatus Van Duzee, Liancalus pterodactyl sp. n., Liancalus querulus Osten Sacken, Liancalus similis Aldrich, and Liancalus sonorus sp. n. Lectotypes are designated for the following species: Liancalus genualis, Liancalus hydrophilus, Liancalus querulus, and Liancalus similis. The species are illustrated, a key to males and females is provided, and their distributions mapped. Adults of Liancalus are some of the largest species of Dolichopodidae and commonly occur on waterfalls and vertical seeps.     

Black-tie dress code: two new species of the genus Toxomerus (Diptera, Syrphidae)

Toxomerus hauseri Mengual sp. n. and Toxomerus picudus Mengual sp. n. are described from Peru and Ecuador respectively. Toxomerus circumcintus (Enderlein, 1938) is treated as a valid species and not considered synonym of Toxomerus marginatus, and Toxomerus ovatus (Hull, 1942) is considered junior synonym of Toxomerus nitidus (Schiner, 1868). An identification key for the Toxomerus species with dark abdomens is given along with diagnoses for each studied species.     

Radiation of the Oriental phlebotomine sand flies (Diptera: Psychodidae)

Abstract The historical biogeography of phlebotomine sand fly taxa Hertigia, Warileya, Phlebotomus (Idiophlebotomus), P. (Spelaeophlebotomus), P. (Anaphlebotomus), and P. (Euphlebotomus) and the Phlebotomus (Euphlebotomus) argentipes species complex was investigated using phylogenetic inference from comparative genital morphology, distribution of ancestral taxa, fossil evidence and geological age. Idiophlebotomus and Euphlebotomus occur in the Oriental region with one species from northeast Australia, whereas Anaphlebotomus occurs both in the Afro‐tropical and Oriental regions. These disjunct distribution patterns across the Oriental region and the present day distribution are likely to be vicariance due to break of Gondwanaland. Fossil records, extant taxa distribution, phylogenetic analysis of the Old World Phlebotominae and paleogeography suggest that ancestors of Idiophlebotomus and Euphlebotomus originated apparently in the Cimmerian continent of northern margin of Gondwanaland in the early Permian (290 million years ago, MYA) and subsequently radiated in the Mesozoic by tectonic vicariance. The Phlebotomus argentipes species complex occurs in the South and South‐east Asian countries and transmits the protozoan parasite Leishmania donovani that causes visceral leishmaniasis (Kala‐azar) in India, Bangladesh and Nepal. The phylogeography of P. argentipes was caused through vicariance followed by dispersal events from 5O MYA (the Eocene) until the Recent era.     

Key to Dohrniphora males (Diptera: Phoridae) of the Australasian and Oriental Regions with descriptions of new species

A key to males of the Australasian and Oriental species of Dohrniphora is provided. Twenty-five new species are described and two new synonyms proposed.