The species of Eilema Hübner, [1819] sensu lato present in Europe and North Africa (Lepidoptera: Erebidae: Arctiinae: Lithosiini).

The species of Eilema Hübner, [1819] sensu lato, present in Europe and North Africa, are studied on the basis of morphological characteristics and molecular genetics. Images of adults, genitalia of both sexes, immature stages, as well as phylogenetic trees obtained from the combined analysis of three different genetic markers are presented. Data on life cycles, food plants, and geographic distribution are also included. The morphological differences observed within Eilema sensu lato have led the authors to create the genera Indalia gen. nov. and Pseudokatha gen. nov. New combinations are stablished: Manulea iberica (Mentzer, 1980) st. rest., comb. nov.; Indalia marcida (Mann, 1859) comb. nov.; Indalia predotae (Schawerda, 1927) comb. nov.; Indalia albicosta (Rogenhofer, 1894) comb. nov.; Indalia interposita (Rothschild, 1914) comb. nov.; Indalia uniola (Rambur, [1866]) comb. nov.; Indalia lutarella (Linnaeus, 1758) comb. nov.; Indalia pygmaeola (Doubleday, 1847) comb. nov.; Pseudokatha rungsi (Toulgoët, 1960) comb. nov., and Eilema albicosta witti Kobes, 1993 syn. nov.

Extremely low neonicotinoid doses alter navigation of pest insects along pheromone plumes.

The prevailing use of neonicotinoids in pest control has adverse effects on non-target organisms, like honeybees. However, relatively few studies have explored the effect of sublethal neonicotinoid levels on olfactory responses of pest insects, and thus their potential impact on semiochemical surveillance and control methods, such as monitoring or mating disruption. We recently reported that sublethal doses of the neonicotinoid thiacloprid (TIA) had dramatic effects on sex pheromone release in three tortricid moth species. We present now effects of TIA on pheromone detection and, for the first time, navigational responses of pest insects to pheromone sources. TIA delayed and reduced the percentage of males responding in the wind tunnel without analogous alteration of electrophysiological antennal responses. During navigation along an odor plume, treated males exhibited markedly slower flights and, in general, described narrower flight tracks, with an increased susceptibility to wind-induced drift. All these effects increased in a dose-dependent manner starting at LC0.001 - which would kill just 10 out of 106 individuals - and revealed an especially pronounced sensitivity in one of the species, Grapholita molesta. Our results suggest that minimal neonicotinoid quantities alter chemical communication, and thus could affect the efficacy of semiochemical pest management methods.

Diversity of piRNA expression patterns during the ontogeny of the German cockroach.

The Piwi-interacting RNA (piRNA) system is an evolutionarily conserved mechanism involved in the control of transposable elements and maintenance of genomic stability, especially in germ line cells and in early embryo stages. However, relevant particularities, both in mechanism and function, exist across species among metazoans and even within the insect class. As a member of the scarcely studied hemimetabolan group, Blattella germanica can be a suitable reference model to study insect evolution. We present the results of a stringent process of identification and study of expressed piRNAs for B. germanica across 11 developmental stages, ranging from unfertilized egg to nymphs and adult female. Our results confirm the dual origin of piRNA in this species, with a majority of them being generated from the primary pathway, and a smaller but highly expressed set of sequences participating in the secondary ("ping-pong") reamplification pathway. An intriguing partial complementarity in expression is observed between the piRNA of the two biogenesis pathways, with those generated in the secondary pathway being quite restricted to early embryo stages. In addition, many piRNAs are exclusively expressed in late embryo and nymphal stages. These observations point at piRNA functions beyond the role of transposon control in early embryogenesis. Our work supports the view of a more complex scenario, with different sets of piRNAs acting in different times and having a range of functions wider than previously thought.

Comparison of Attraction and Trapping Capabilities of Bucket- and Delta-Style Traps With Different Pheromone Emission Rates for Gypsy Moths (Lepidoptera: Erebidae): Implications for Understanding Range of Attraction and Utility in Surveillance.

Delta- and bucket-style (Universal or Unitrap) traps baited with 1 standard survey lure and 1/3 and 3 lures were compared for their attractiveness and trapping efficiencies for gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), males. With bucket traps, the numbers of males attracted to within 2 m of traps and the proportion of these actually captured were identical among the three doses although the percentage of attracted males actually captured in bucket traps was low, less than 15%. A three-lure delta trap attracted about 70% more males than traps with the two lower doses. Capture efficiencies were above 80% for 1/3- and one-lure traps and about 60% for traps baited with three lures. The number of males captured in delta traps was equivalent for the three doses although our observations also suggest that a delta trap baited with three lures drew males from a wider range than lower dose lures and therefore would be a more sensitive trap for detecting incipient populations. We also noted that males tended to arrive in clusters, suggesting that attraction over moderate distances requires periods when the wind direction is fairly constant. This observation coupled with the great variability in the direction of male arrival to the traps also suggests that important changes in the area of influence of the plume are driven in such forested areas by slower but greater changes in wind direction compared with open habitats.

Simulation Modeling to Interpret the Captures of Moths in Pheromone-Baited Traps Used for Surveillance of Invasive Species: the Gypsy Moth as a Model Case.

When pheromone traps are used for detection of an invasive pest and then delimitation of its distribution, an unresolved issue is the interpretation of failure to capture any target insects. Is a population present but not detected, a so-called false negative? Using the gypsy moth (Lymantria dispar) as an exemplar, we modeled the probability of males being captured in traps deployed at densities typical for surveillance (1 per 2.6 km2 or 1 per mi2) and delimitation (up to 49 per 2.6 km2). The simulations used a dynamic wind model generating a turbulent plume structure and varying wind direction, and a behavior model based on the documented maneuvers of gypsy moths during plume acquisition and along-plume navigation. Several strategies of plume acquisition using Correlated Random Walks were compared to ensure that the generated dispersions over three days were not either overly clumped or ranged many km. Virtual moths were released into virtual space with patterns mimicking prior releases of gypsy moth males in Massachusetts at varying distance from a baited trap. In general, capture rates of virtual and real moths at varying trap densities were similar. One application of this approach was to estimate through bootstrapping the probabilities of not detecting populations having densities ranging from 1 to 100 moths per 2.6 km2 and using traps that varied from 25 to 100 % in their efficiencies of capture. Low-level populations (e.g., 20-30 per 2.6 km2) often were not detected with one trap per 2.6 km2, especially when traps had low efficiencies.

Modeling Optimal Strategies for Finding a Resource-Linked, Windborne Odor Plume: Theories, Robotics, and Biomimetic Lessons from Flying Insects.

Male moths locate females by navigating along her pheromone plume, often flying hundreds of meters en route. As the first male to find a calling female is most apt to be her mate, this can be termed "a race to find the female" and it is assumed to be under strong selective pressure for efficiency and rapidity. Locating a distant, odor-linked resource involves two strategies. The first is to contact the outer envelope of the odor plume. When wind direction is relatively invariant, the plume stretches and then crosswind flights may be favored, although when wind direction shifts over 60°, upwind and downwind paths may be optimal. Alternatively, the path may be random with respect to the direction of wind flow, with periodic changes in direction, as in either Lévy or Random Walks. After first detecting the pheromone, a second strategy follows: moths navigate along the plume by heading upwind when the pheromone is detected, with crosswind casting to re-establish contact if the plume is lost. This orientation path is not straightforward in nature, however, because atmospheric turbulence fragments the plume, thereby creating large odor gaps. Furthermore, a shifting wind direction can lead the responder out of the plume. One way to explore which strategies are optimal for enabling initial contact with the plume and subsequent navigation is through modeling of plumes' dispersal and of insects' flight strategies. Our simulations using the flight characteristics of the male gypsy moth (Lymantria dispar) suggest that search strategies similar to Lévy Walks are most apt to result in a high probability of contact with plumes. Although a searching trajectory aimed predominately crosswind performed almost as well as those with a random orientation when wind direction was relatively stable, downwind biased trajectories were least successful. A random orientation with respect to immediate wind flow, as used in our simulations of Lévy and Random Walks, seems optimal both for initial discovery of the plume and likelihood of locating an odor source. In the two available direct field observations, moths adopted a random orientation with respect to concurrent wind direction.

Electroantennographic resolution of pulsed pheromone plumes in two species of moths with bipectinate antennae.

Trains of 20-ms-duration pulses of pheromone were delivered at rates of 1-33 Hz to antennal preparations of males of Bombyx mori and Lymantria dispar, two moth species with bipectinate antennae. Resolution of rapidly pulsed plumes of pheromone was not compromised by a complex antennal morphology or by moderate changes in wind speed (25-50 cm/s). Fourier analysis of the electroantennograms resolved the temporal structure of the signal at frequencies up to 25 Hz for B. mori and up to 5 Hz for L. dispar. The ability of these sensory structures to identify the original (unchanged) frequency of the pulse train is particularly noteworthy because air is slowed by about an order of magnitude as it passes through bipectinate antennae. Although an unchanging frequency in slowed airflow may be counterintuitive, this flow pattern, and its effects on odorant patch shape and spacing, is explained from fluid mechanical principles (i.e., the principle of continuity). An unchanging frequency suggests that as decelerating air passes through a bipectinate antenna, the slowed patches of odorant are stretched, thinned, and brought closer together by the same factor with which they are slowed.

Responses of the olfactory receptor neurons of the corn stalk borer Sesamia nonagrioides to components of the pheromone blend and their inhibition by a trifluoromethyl ketone analogue of the main component.

Two types of olfactory hairs and three types of olfactory receptor neurons (ORN) have been characterized on the antennae of male Sesamia nonagrioides Lef for the first time. Type A sensilla housed a cell which fired large spikes in response to (Z)-11-hexadecenyl acetate (Z11-16:Ac), the major component of the sex pheromone, and a second cell firing smaller spikes in response to (Z)-11-hexadecenal (Z11-16:Ald), a minor component of the pheromone blend. Type B sensilla housed one cell firing large spikes to Z11-16:Ac and a cell firing smaller spikes to another minor component of the pheromone blend, (Z)-11-hexadecenyl alcohol (Z11-16:OH). No cell responding to dodecyl acetate, another minor component of the natural extract, was found. Fluorinated ketones were tested as inhibitors of the cell responses to pheromone compounds. The fluorinated derivatives tested, (Z)-11-hexadecenyl trifluoromethyl ketone (Z11-16:TFMK), n-hexadecyl trifluoromethyl ketone (16:TFMK), (Z,E)-9,11-tetradecadienyl trifluoromethyl ketone (Z9,E11-14:TFMK), 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP), (Z)-11-tetradecenyl trifluoromethyl ketone (Z11-11:TFMK) and 1,1-difluoro-(Z)-11-hexadecenyl methyl ketone (Z11-16:DFMK), had no or only weak excitatory effects. However, the neuron responses to the pheromone compounds were significantly decreased in the presence of a constant stimulation with Z11-16:TFMK and the effect was reversible. The latencies of the responses to the acetate and aldehyde cells were significantly increased. The effects were not specific, since Z11-16:TFMK also inhibited the responses of the ORNs of Spodoptera littoralis Boisd. Correspondingly, Z9,E11-14:TFMK, an analogue of the main component of the pheromone of this latter insect, inhibited responses of S nonagrioides ORNs. Implications of these results on the utilization of Z11-16:TFMK as a communication disruptant are discussed.

Sex pheromone of the oak processionary moth Thaumetopoea processionea. Identification and biological activity.

The sex pheromone of the oak processionary moth Thaumetopoea processionea has been characterized from female gland extracts as a mixture of (Z,Z)-11,13-hexadecadienyl acetate (1), (E,Z)-11,13-hexadecadienyl acetate (3) and (Z,Z)-11,13-hexadecadienol (2) in 88:7:5 ratio. The amount of the major compound 1 was 20-30 ng/gland. No trace of (Z,Z)-11,13-hexadecadienal was found in the extract, and therefore, T. processionea appears to be the only "summer" processionary moth lacking this compound as a pheromone compound. The alcohol 2 had also been previously found but is electrophysiologically inactive, and in wind tunnel assays it lowers the number of contacts with the source when mixed with the major compound 1. The major component 1 elicited males to display the complete behavioral sequence, but the amount of chemical needed was unexpectedly high in comparison to the activity displayed by virgin females and gland extracts. (E,E)-11,13-hexadecadienyl acetate (5) inhibits the attractant activity of the major component 1 when mixed with 1 in 1:10 and 1:1 ratios. The main constituent 1 is active in the field, but its tendency to isomerize into the corresponding E,E isomer (5) must be considered if effective formulations are to be prepared.

Antennal resolution of pulsed pheromone plumes in three moth species.

Male antennae of Cadra cautella, Pectinophora gossypiella, and Spodoptera exigua were presented with 20-ms-duration pulses of their two-component pheromone at rates of 1 to 33 Hz. Fourier analyses of electroantennograms resolved the temporal structure of trains of pheromone filaments delivered at up to 33 Hz for C. cautella and S. exigua and 25 Hz for P. gossypiella. Pheromone components tested separately for each species were generally equivalent in filament resolution to complete blends. Ambient temperatures of 18, 23 and 28 degrees C affected filament resolution only slightly, with poorer ability to discriminate rapidly pulsed signals at 18 degrees C. The question of how, or indeed if, such frequencies are conserved beyond the peripheral nervous system, remains.