Morphological discrimination of Aphis gossypii (Hemiptera: Aphididae) populations feeding on Compositae

Aphis gossypii Glover is a polyphagous aphid pest with a worldwide distribution. However, there is evidence that on a global scale the name A. gossypii is being applied to a number of forms with different life cycles and/or host-plant associations. Morphometric variation of A. gossypii samples from crops and non-cultivated plants in many parts of the world was examined, to determine whether this variation is correlated with the hosts from which the aphids originated. Samples of A. gossypii were collected from Cucurbitaceae and Malvaceae in Europe, and from Compositae in various parts of the world. Morphometric data for 13 parameters measured from 97 clonal lineages (728 specimens) and 27 field-collected samples (313 specimens) were analysed by a series of canonical variates analyses, using the field sample/clonal lineage as grouping factor. Clonal lineages were reared on a common host in controlled conditions to standardize the effect of host and environment on morphology. The analyses provided a clear morphometric separation of the aphids originating from Compositae and those collected on Cucurbitaceae and Malvaceae, regardless of the geographical origin of the aphids and the host plant on which they were reared. This indicates that within A. gossypii there are two widely distributed host races or subspecies with different plant family associations. The taxonomic implications are discussed.     

Male brooding behaviour of the giant water bugLethocerus deyrollei vuillefroy (Hemiptera: Belostomatidae)

The male brooding behaviour ofLethocerus deyrollei was investigated. Eggs were laid as masses on sticks above the water surface. Males did not leave the sticks until the eggs hatched. They mainly stayed at the bases of the sticks in water in the day, and frequently climbed up at night covering the egg-masses with their bodies. Eggs with male brooding had a 94.3% hatching rate. Eggs without male brooding failed to hatch and desiccated. Eggs with brooding considerably increased in wet weight in development; eggs without brooding decreased in wet weight. Eggs without male brooding and artificially supplied with water had a 93.2% hatching rate. Male brooding is considered to supply eggs with water.     

The role of water vapour in the orientation behaviour of the blood-sucking bug Triatoma infestans (Hemiptera,Reduviidae)

The behavioural response to water vapour of the haematophagous bug Triatoma infestans was analysed. Dry or humid discrete sources at different temperatures were used as stimuli for insects walking on a locomotion compensator. Humidity significantly increased the tendency of these bugs to orientate towards thermal sources. Furthermore, humid sources at room temperature were attractive to T. infestans, but this effect was limited to short-range distances. On the other hand, dynamic sources, i.e. airstreams carrying different water vapour contents did not affect the spontaneous anemotactic behaviour of this species, neither in sign (positive) nor in intensity. The anemotactic behaviour was also not influenced by the physiological water balance state of the bugs. Results are discussed in relation to the cues released by living hosts of triatomine bugs and in relation to their responses to air-currents.     

Preference-performance linkage of the xylem feeding leafhopper, Homalodisca vitripennis (Hemiptera Cicadellidae)

Insect species exhibiting a weak linkage between adult preference and immature performance have frequently been shown to be prone to outbreaks. We used choice and no-choice tests to examine the preference-performance linkage of the xylem fluid-feeding leafhopper, Homalodisca vitripennis Germar. Leafhoppers were offered a choice of hosts common to their native range and also a choice from hosts where they have been recently introduced. Behavior (residence preference, oviposition preference, and consumption rates) was quantified in choice tests. Performance (development of immature leafhoppers, fecundity, body weights, and survivorship) was quantified in no-choice tests. Virtually all aspects of leafhopper behavior and performance varied with host species, yet there were no linkages between adult preference and immature performance. Lagerstroemia indica and Citrus sinensis were the preferred hosts, but both species supported <30% of neonate development until the second stadia. Glycine max was the superior developmental host with development to the adult stage exceeding 40%, but this host was seldom used by adult leafhoppers. Adult preference reflected aspects of adult performance including increases in fecundity, body weights, and survivorship. These preference-performance linkages were impacted by environmental context, insect reproductive status, and insect feeding history. Essential amino acids were consistently correlated with performance of both adult and developing insects; relationships between nutrients and preference were less consistent. The weak linkage of adult preference and immature leafhopper performance are discussed in terms of outbreaks of H. vitripennis.     

Nutritional effects on male calling behaviour in the variable field cricket

In the variable field cricket, Gryllus lineaticeps, females prefer higher chirp rates and longer chirp durations in male calling song. Higher chirp rates are energetically more expensive to produce, but the energetic cost of calling does not vary with chirp duration. We tested the hypothesis that nutrition affects male chirp rate and chirp duration. Full-sibling brothers of similar age were placed on high- and low-nutrition feeding regimes. There was no effect of feeding regime on male weight; neither group showed a significant change in weight, and the two groups did not differ from each other in weight change. However, males on the high-nutrition feeding regime both called more frequently and called at higher chirp rates when they did call. The two groups did not differ in chirp duration, the duration of pulses within chirps or chirp dominant frequency. These results suggest that females select mates based on one nutrition-dependent call character (chirp rate) and one nutrition-independent call character (chirp duration). In addition, because males in the two groups did not show significant differences in weight change, and because males on the high-nutrition feeding regime engaged in energetically more expensive calling, these results suggest that males invest any excess energy above their basic maintenance requirements in the production of call types that increase their attractiveness to females. The absence of a relationship between body condition and calling song structure for males in the field may be a consequence of this pattern of energy allocation. Copyright 1999 The Association for the Study of Animal Behaviour.     

Distribution and molecular characterization of distinct Asian populations of Bemisia tabaci (Hemiptera: Aleyrodidae) in Japan

Bemisia tabaci (Gennadius) is considered to be the most economically important pest insect worldwide. The invasive variant, the Q biotype of B. tabaci was first identified in 2004, and has caused significant crop yield losses in Japan. The distribution and molecular characterization of the different biotypes of B. tabaci in Japan have been little investigated. In this study, B. tabaci populations were sampled from the Japanese Archipelago, the Amami Archipelago and the Ryukyu Islands between 2004 and 2008, and the nucleotide sequences of their mitochondrial cytochrome oxidase I genes were determined. Bayesian phylogenetic relationship analysis provided the first molecular evidence that the indigenous Japanese populations could be separated into four distinct genetic groups. One major native population from the Japanese Archipelago, given the genetic group name Lonicera japonica, was separated into an independent group, distinct from the other genetic groups. The second major population, the Nauru biotype in the Asia II genetic group, was identified in the Amami Archipelago and the Ryukyu Islands. Two distinct minor genetic groups, the Asia I and the China, were also identified. One invasive B‐related population belonging to the Mediterranean/Asia Minor/Africa genetic group has been identified in Honshu. All lineages generated by the phylogenetic analyses were supported by high posterior probabilities. These distinct indigenous B. tabaci populations developed in Japan under geographical and/or biological isolation, prior to recent invasions of the B and Q biotypes.     

Soldier behaviour and division of labour in the aphid genus Pemphigus (Hemiptera, Aphididae)

Summary. We devised a test for quantitatively measuring the defensive behaviour of individual aphids of the gall generations of the genus Pemphigus. Five species (P. spyrothecae, P. gairi, P. bursarius, P. phenax, and P. protospirae) were shown to have soldiers, but the early instars of Pemphigus populi showed no aggressive behaviour. A higher proportion of the first instars of P. spyrothecae showed aggressive behaviour, compared with the other four soldier-producing species. Although the first instars were always the most likely to be aggressive, later instars also showed significant levels of aggression in all the soldier-producing species. Soldier behaviour was elicited by a range of stimuli. A live, restrained, predator was the most effective stimulus tested, but physical stimulation (with a paintbrush) enhanced the attack rate. The aphids could distinguish between lures soaked in water and those soaked in aphid haemolymph, which elicited a higher level of response. First instars of the early and late gall generations of P. spyrothecae were equally likely to attack predators. Although the species with the most specialized soldiers (P. spyrothecae) also had the most prolonged gall phase, this is clearly not the only factor that is important in the evolution of soldiers in this genus.     

Feeding and defaecation behaviour of Triatoma patagonica (Del Ponte, 1929) (Hemiptera: Reduviidae)

Among the vectors of Chagas disease, Triatoma patagonica is a species in the process of adaptation to the human environment being recently registered in urban and suburban zones. However, its importance as a vector of Chagas disease is unknown. The aim of this work was to evaluate two aspects of vectorial competence: the feeding behaviour and the defaecation pattern. These processes were studied in females of T. patagonica fed ad libitum on a restrained pigeon. The results showed that the blood meal size was negatively correlated with the time of first defaecation (r = -0.42). The first defaecation was emitted before the first 10 min and defaecations during feeding were frequent. A total of 73% of females, defaecated during the first 30 min post-feeding. These results suggest that if this species subsequently colonizes the domicile, it would be capable of transmitting Trypanosoma cruzi.     

Acoustic communication in the trilling field cricket,Gryllus rubens (Orthoptera: Gryllidae)

Male field crickets produce calling songs that are used for attracting conspecific females for mating. Acoustic communication was studied in the trilling field cricket, Gryllus rubens.A trilled calling song consists of a continuous train of sound pulses, each of which was repeated at a stereotyped rate. Singing males were recorded at different temperatures. The pulse period of the calling song decreased with increasing temperature; there was less effect of temperature on pulse duration. Female phonotaxis was studied on a noncompensating, spherical treadmill. In two-stimulus (choice) playback experiments, females preferred the conspecific trilled song over the chirped calling song of a sympatric species, Gryllus fultoni.This preference persisted even when the song of G. fultoniwas 6 dB louder. Females also discriminated between synthetic trills having different pulse periods; females chose trills with the conspecific pulse period over trills having lower and higher pulse periods.     

Estimating parasitism levels in Lygus spp. (Hemiptera: Miridae) field populations using standard and molecular techniques

Host dissection, host rearing and PCR analysis were used to estimate parasitism level and identify the parasitoid complex in Lygus spp. populations in alfalfa. Parasitism level estimates by PCR were higher than by other methods. The PCR results from all samples tested with available primers were consistent with Peristenus pallipes, although the parasitoid was identified as Peristenus near mellipes by morphological characters.     

Mating behaviour in Tetraneura nigriabdominalis Sasaki (=akinire Sasaki) (Hemiptera,Pemphiginae)

Summary

The sex-ratio and behavioural mating peculiarities of Tetraneura nigriabdominalis have been investigated. A morphological study by SEM revealed the developmental stages of sex-attractant pheromone glands on the hind tibiae of females, the morphology of the chemiosensilla on the male antennae, and peculiar microsculptures on abdominal stemites which may be interpreted as an anchorage system favouring copulation.     

Molecular phylogeny of the genus Tibicina (Hemiptera, Cicadidae): rapid radiation and acoustic behaviour

To estimate the potential contribution of ethological and ecological parameters to the mechanisms of species formation and species isolation in the Palearctic cicada genus Tibicina , we constructed a molecular phylogenetic hypothesis of extant Tibicina species. Seven mitochondrial genes and a fragment of a nuclear gene were sequenced (3046 bp). Mitochondrial genes included 547 informative sites but the nuclear gene was too conserved to be included in the analysis. The tree was characterized by a basal polytomy indicating that Tibicina species arose rapidly. Such rapid radiation might explain the low divergence in the acoustic communication observed between species. Parameters describing habitat selection and acoustic communication were mapped onto the tree. A shift in habitat selection accompanied by acoustic changes might have contributed to one speciation event. The stochastic distribution of the same acoustic characters on the other branches of the tree implies, however, that the subtle acoustic differences between species could be the result of previous speciation events and independent evolutionary histories, rather than having contributed themselves in the speciation and isolation processes.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 611–626.     

The effect of experience on the selective behaviour of song thrushes feeding on artificial populations ofCepaea (held)

Song thrushes fed on populations of bread-stuffedCepaea shells. The results indicate that experience influences the selective behaviour of thrushes for both shell colour and shell size. Such behaviour could lead to frequency dependent selection in natural populations. Within the ranges of size and colour offered, thrushes learned from a colour rather than a size experience when both were varied simultaneously.     

Homing in the field cricket,Gryllus campestris

Homing ability of the cricket Gryllus campestriswas experimentally studied in the field after passive and active displacements. Whatever the weather conditions and the nature of the displacement, crickets (18/18) home directly when they are located between 5 and 15 cm from their burrow by performing real-time orientation. When moved by the experimenter between 15 and 55 cm away from home, some crickets (26/43) can retrieve their burrow by systematic searching only after winding inward trips but they get lost (0/18) beyond 55 cm. After self-generated movements between 5 and 85 cm away from home, crickets (33/35) return to their burrow under blue sky, but they cannot home as well under overcast sky (22/34 from 5 to 65 cm and 0/5 beyond). The volatile memory orientation system allowing path integration is based on the polarized skylight of the sun.     

The ecology and behaviour of a marine insect, Halobates fijiensis (Hemiptera: Gerridae)

Observations were made in Fiji on the adaptive strategies of a marine gerrid, Halobates fijiensis , a species of the only genus of insects to have successfully colonized the open sea. The immature stages spend most of their time in flotillas on sheltered water close to mangroves, whereas adults usually occur singly and on both sheltered and open water behind the protecting reef systems. Wind has a decisive influence on the distribution of H. fijiensis: in strong onshore winds, all stages, including adults, remain close to the shelter of mangroves, but in calm conditions, older immatures venture considerable distances from the mangroves. Halobates fijiensis feed on floating, dead insects. Adults of the chironomid fly Tanytarsus halophilae , whose larvae live on intertidal sea-grasses, accounted for over 60% of the prey items recorded. Halobates fijiensis feeds at around the time of high water, either as individuals or in small, well-dispersed groups. Eggs are laid on intertidal turtle grass (Syringodium) , green coralline algae (Halimeda) or occasionally coral rubble, at or shortly after the point of low water on days of extreme low spring tides. Halobates fijiensis is preyed upon by the robber-fly Clinopogon scalaris (Diptera: Asilidae). Field observations showed that there is a clear effect of group size on the distance at which an approaching predator model is detected.     

Expression of allatostatins in the Mediterranean field cricket, Gryllus bimaculatus de Geer (Ensifera, Gryllidae)

The allatostatin (AST) type A gene of the cricket Gryllus bimaculatus encodes a hormone precursor including at least 14 putative peptides with a common C-terminus Y/FXFGL/Iamide. By RT-PCR we have analyzed the expression of the allatostatin precursor in various tissues of 0-21 days old adult virgin and mated females. In 3-day-old virgin females, the gene is strongly expressed in the brain (oesophageal ganglion), the suboesophageal ganglion and the caecum, but to a lower extent in other parts of the digestive tract (ileum, midgut, colon), and in various other tissues such as the fat body, ovaries and female accessory reproductive glands. In the brain and ovaries of virgin females, the AST expression is rather constant throughout adult life, whereas in brains of mated animals, expression is low until day 7, but increases sharply from day 8 onwards to reach values triple those before day 7. In ovaries of mated animals AST gene expression is also age-dependent, with high expression rates during the first 4 days after imaginable moult, a second but smaller peak from day 15 to 21, and very low values in between. In the fat body of virgin crickets allatostatin expression is high during the first 9 days after ecdysis and declines thereafter, whereas in mated animals two peak values, day 1 and day 6, are observed, and a third peak in older animals.     

True bugs (Hemiptera,Heteroptera) as psyllid predators (Hemiptera,Psylloidea)

Data on natural enemies of psyllids are rare and can usually be found in papers about economically significant species. During an investigation of psyllid fauna in Serbia, natural enemies were investigated, too. True bugs were the most numerous among them. From 28 psyllid species, 21 species of true bugs from families Anthocoridae and Miridae were reared. Seven species of Anthocoridae were identified: Anthocoris amplicollis (Horváth, 1839), Anthocoris confusus Reuter, 1884, Anthocoris nemoralis (Fabricius, 1794), Anthocoris nemorum (Linnaeus, 1761), Orius majusculus Reuter, 1884, Orius minutus (Linnaeus, 1758) and Orius niger Wolff, 1811. The following 14 species of Miridae were identified: Atractotomus mali Meyer-Dür, 1843, Campylomma verbasci (Meyer-Dür, 1843), Deraeocoris flavilinea (A. Costa, 1862), Deraeocoris ruber (Linnaeus, 1758), Deraeocoris lutescens (Schilling, 1836), Heterocordylus genistae (Scopoli, 1763), Hypseloecus visci (Puton, 1888), Malacocoris chlorizans Panzer, 1794, Miris striatus (Linnaeus, 1758), Orthotylus marginalis Reuter, 1884, Psallus assimilis Stichel, 1956, Psallus quercus Kirschbaum, 1856, Psallus flavellus Stichel, 1933 and Pseudoloxops coccinea (Meyer-Dür, 1843). The aim of the research was to provide list of true bugs recorded as predators of psyllids in order to preserve their diversity and significance, especially on cultivated plants.