Hormonal Control of Egg Dumping and Guarding in the Lace Bug, Gargaphia solani (Hemiptera: Tingidae)

This study examines the effect of juvenile hormone (JH) or a similarly acting juvenoid on the expression of maternal egg guarding and its life history alternative, egg dumping, in the lace bug, Gargaphia solani Heidemann. JH manipulations were indirect: methoprene, a synthetic JH analog, and precocene II, an allatocidal phytochemical commonly used to reduce JH synthesis, were applied exogenously to test the hypothesis that high JH titers promote egg production and egg dumping behavior, while low titers terminate egg production and initiate maternal care. As predicted, egg dumpers treated with precocene II ignored dumping opportunities and became egg guarders. Similarly, egg guarders that were treated with methoprene became gravid within 2 days and abandoned their eggs to become egg dumpers. These manipulations suggest that hormones can trigger the expression of both egg dumping and egg guarding in G. solani even when environmental conditions are inappropriate.     

Effect of predators and host phenology on the maternal and reproductive behaviors ofGargaphia lace bugs (Hemiptera: Tingidae)

Lace bugs of the genus Gargaphia specialize on taxonomically and ecologically diverse host plants. To examine the impact of predation pressure and host phenology on Gargaphia subsocial and reproductive behavior, we compared G. tiliae, a woodland species restricted to riparian trees in the genus Tilia, and G. solani, a specialist on Solanum in early successional habitats. Both lace bug species exhibit maternal care of eggs and nymphs. Predator densities associated with Solanum were higher than those associated with Tilia and were correlated with higher levels of maternal aggression exhibited by G. solani. In both habitats, artificial exclusion of predators significantly increased nymphal survivorship over maternally guarded broods. Both species reduced the costs associated with maternal care by ovipositing into the egg masses of conspecifics. Gargaphia solani and G. tiliae differed most strikingly in voltinism and thus the potential for iteroparity. Leaf age determined the reproductive future of G. tiliae nymphs independent of photoperiod or temperature. Feeding on plants with young foliage was sufficient to trigger oviposition. Constraints imposed by host plants on life-history patterns and maternal options are discussed.     

Maternal care in the red-headed spruce web-spinning sawfly,Cephalcia isshikii (Hymenoptera: Pamphiliidae)

We describe oviposition and maternal behavior in the sawfly Cephalcia isshikiiand examine the adaptive significance of this behavior. Females deposited eggs in a single but loose cluster on needles of terminal twigs of spruces, Piceaspp., and remained with the eggs usually on the underside of the twig facing toward the tip. The female attended her eggs until death without taking food but did not follow the first-instar larvae that moved from natal needles even if she survived until then. When the female was disturbed, she usually moved toward the source and attempted to bite it. Though at much lower frequencies, this aggressive behavior was also observed in gravid females and even in males. Field observations and female removal experiments indicated that the female enhanced the survival of the eggs through the reduction of arthropod prédation.     

Copulation Is Not a Prerequisite to Male Reception of Eggs in the Golden Egg Bug Phyllomorpha laciniata (Coreidae; Heteroptera)

Females of the golden egg bug, Phyllomorpha laciniata, lay eggs on the backs of conspecifics. Male response to female oviposition attempts is either passive or resistant. Passive males remain still during oviposition, while resistant males move repeatedly and thereby delay or avoid being encumbered. We investigated how previous mating experience affected male acceptance of eggs. Males from two Spanish populations, from Andalusia and Catalonia, were allowed to mate with single females repeatedly. These experimental pairs were then presented with either a single, nonmating male or a pair in copula. We expected mating partners to resist oviposition attempts less strongly than nonmating males but no differences were detected. However, there was a significant difference in behavior exhibited by males from the two populations; males from Catalonia were relatively passive but males from Andalusia routinely resisted encumbrance. Predation pressure and the availability of receptive females may explain the observed differences between the populations.     

Zinc fertilisation increases tolerance to Rhizoctonia solani (AG 8) in Medicago truncatula

The effect of Zn fertilisation on tolerance of Medicago truncatula to infection by the root-rotting pathogen Rhizoctonia solani (AG 8) was studied in a field survey and in two experiments in controlled conditions. From the field survey, the concentration of Zn in the shoots of medics was found to be inversely related to the severity of disease on the root. Overall, the addition of Zn to Zn-deficient soil in controlled environment experiments resulted in reduced yield loss in the presence of R. solani, a reduction in disease score and no change in the concentration of nutrients in the shoots. However, under Zn deficiency, increasing levels of added R. solani resulted in significant yield loss, an increase in disease score and a reduction in concentration of Zn in the roots. This occurred despite a decrease in the number of infection sites caused by the fungus on the root and a lower amount of R. solani DNA extracted in medics deficient in Zn compared with plants supplied with Zn. While plants supplied with Zn were able to maintain a stable concentration of Zn in the shoots, the concentration of Zn in the roots also declined with increasing levels of R. solani. In conclusion, Zn application does not directly inhibit infection by R. solani, nor reduce its pathogenicity, but it does strongly increase root growth. The net result is that Zn-sufficient plants are more tolerant to the effects of root pruning by the fungus than Zn-deficient plants.     

Comparison of Substrate-Borne Vibrational Signals of Two Congeneric Stink Bug Species, Thyanta pallidovirens and T. custator accerra (Heteroptera: Pentatomidae)

Vibrational signals (songs) were recorded and compared for two stink bug species, Thyanta pallidovirens and T. custator accerra. Females of both species produced two songs. Male T. pallidovirens also produced two songs, whereas male T. c. accerra produced four. Songs emitted by females of both species were comparable in structure and function, as was one of the male-produced songs. During the courtship phase of mating behavior, males of both species emitted a song with similar function but different temporal and spectral properties. Basic properties of songs, such as the dominant frequencies, were similar to those of songs of other pentatomid species, but the extensive use of frequency modulation and overlapping duets were novel. Differences in songs, combined with differences in male-produced pheromones, may play a role in the reproductive isolation of these congeners.     

Wing Movement Behavior in Long- and Short-Winged Morphs of the Flightless Bug Pyrrhocoris apterus L. (Heteroptera: Pyrrhocoridae)

The aim of the present paper was to study, with the use of video-recordering and computerized methods, the flight and wing movement behavior in two wing morphs of the flightless bug Pyrrhocoris apterus during the first 14 days of their adult life. We demonstrated the capability of macropterous males and females of this heteropteran to flap their fore- and hindwings for the first time. Flight was not observed in any of the tested males and females. We revealed that wing flapping does not occur earlier than on the fourth and fifth day after adult emergence in males and females, respectively. Time-series analysis of the obtained data showed that the maximum activity of wing flaps is limited to the light phase of the 12-h light/12-h dark photocycle, with the peak occurring in the morning, i.e., about 3 h after turning the light on. No substantial differences in the peaks of wing flapping activities in males versus females were found. The present paper is the first experimental demonstration of wing flap activity in a representative species with a nonfunctional alary polymorphism.     

Distribution of Care-Giving Effort in a Communally Breeding Lace Bug: Fair Guarding Without Coercion

Cooperative care of offspring is a hallmark of animal sociality, but it is unclear how conflicts over care-giving effort are resolved in taxa that do not use dominance and physical force to induce cooperation efforts in others. To ascertain if taxa without dominance-enforcing traits such as stings or biting mouthparts show conflicts over offspring care, we used a lace bug (Heteroptera: Tingidae) that has communal guarding of young but lacks morphologies for dominance or coercion. In Leptobyrsa decora females oviposit communally and then aggressively guard communal broods from arthropod predators. Since guarding has mortality risks, we tested if individuals lower their own risk by behaving less aggressively than the partner guard. We show that effort towards protecting brood, and thus guard risk of death, is strongly positively correlated between guarding partners. This finding suggests that mechanisms other than dominance or coercion are used by L. decora to establish an equitable and possibly conflict-minimizing distribution of care-giving effort.     

Factors Influencing Bug Diversity (Insecta: Heteroptera) in Semi-Natural Habitats

We investigated the abundance and species richness of heteropteran bugs and explored environmental factors which influence bug diversity in three types of semi-natural habitats (wildflower areas, extensively used meadows, extensively grazed pastures). To cover this topic, it is essential to know how much the relatively young wildflower areas contribute to biodiversity compared with well-established extensive meadows and pastures. Total bug species richness and phytophagous bug species richness were significantly higher in wildflower areas and meadows than in pastures. In wildflower areas, we found the highest number of zoophagous bug species and species overwintering in the egg-stage. Species overwintering as adults were most abundant in meadows. Total number of bug species as well as species richness in either trophic groups and overwintering strategies were significantly positively correlated with vegetation structure. Except for overwintering strategies, the same was true to bug abundance. The bug community based on the number of individuals per species was significantly explained by flower abundance and vegetation structure, accounting for 18.4 and 16.8% of the variance, respectively. Our results indicate that vegetation structure and flower abundance are key factors for bug species richness, abundance and bug species composition. Since wildflower areas and meadows clearly increased bug species richness and contained several specialised bug species that did not occur in pastures, we recommend the promotion of wildflower areas and extensively used meadows in order to restore both high heteropteran diversity and overall insect biodiversity in agricultural landscapes.     

Mycetoma caused by Fusarium solani with osteolytic lesions on the hand: case report

Eumycetoma is a mycotic disease caused by saprophytic soil fungi that are usually inoculated through minor injuries. A case of mycetoma in a Brazilian farmer aged71 years is reported. This patient presented erythema and edema on the dorsal surface of the left hand with multiple crusted and cicatricial lesions. No macroscopic grains were observed. The histopathological findings showed grains consisted of numerous hyphae which stained well with Gomori-Grocott method. This material obtained by cutaneous biopsy was submitted to culture on Sabouraud’s medium and the colonies were identified as Fusarium solani. The radiological studies revealed bone osteolytic lesions and the ultrasound showed pseudocysts and fistulae at the site of this infection. The patient was treated with oral ketoconazole with a good clinical response. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fusarium solani invader of the eggs of the insectPanstrongylus geniculatus in a vivarium

A strain ofFusarium solani sensu Snyder & Hansen invaded the eggs of the insectPanstrongylus geniculatus in a vivarium. None of the invaded eggs hatched. To establish experimentally the pathogenicity of thisFusarium species against the eggs ofP. geniculatus, the fungus and the eggs were incubated together under different relative humidities and temperatures. At 64% relative humidity and 26 °C, the fungus grew well colonizing and penetrating all of the chorions.Three embryos died and were also colonized byF. solani. Only 4 nymphs hatched and survived to day 20. It is concluded that the isolate ofF. solani was capable of colonizing and invading the chorion of the eggs under certain humidity and temperature conditions and cause the death of the embryos.     

An established cell line from the beetle, Xylotrechus pyrrhoderus (coleoptera: Cerambycidae)

Summary A continuous cell line has been established from larval fat body tissues of the cerambycid beetle Xylotrechus pyrrhoderus Bates. These cells were cultured in MGM-450 medium. The cell line, designated as XP-1, showed a heterogeneous population consisting of spherical and spindle-shaped cells with some capacity to adhere and a doubling time of 5 d. The chromosome number of the cell line ranged from 18 to 42 with a mode of 20. Isozyme analysis showed that the cells had patterns distinctive from those of other insect cell lines. The cells were sensitive to insect hormones, and when continuously treated with 20-hydroxyecdysone and juvenile hormone, they assumed a floating elongated-spindle shape and became strongly adherent, respectively.     

A new record of amphisexual care in an insect with exclusive paternal care: Rhynocoris tristis (Heteroptera: Reduviidae)

We describe the first record of amphisexual care in an insect with uniparental male care. Male Rhynocoris tristis are noted for aggressively guarding multiple egg masses. When a male is unable or unwilling to guard eggs, a female that has previously contributed eggs returns to the egg mass and defends it until the eggs hatch. We compared the frequency and intensity of parental aggression in both sexes and found no difference in either form of guarding behavior. Evidence of amphisexual care in R. tristis provides an opportunity to quantify the cost of care in both sexes within a single species.An erratum to this article can be found at     

Counterstrategy to Egg Dumping in a Coreid Bug: Recipient Individuals Discard Eggs from Their Backs

The golden egg bug, Phyllomorpha laciniata Vill. (Heteroptera: Coreidae), is the only terrestrial insect in which females oviposit on the backs of female and male conspecifics. Eggs do not survive unless carried by a bug. Herein, I report laboratory observations that egg-carrying individuals actively brush their backs against the host plant seemingly in an effort to rub off eggs. Egg scraping is more common among individuals carrying many eggs than among those carrying only a few eggs. The most recently received eggs were rubbed off first. Females did not avoid laying eggs on the backs of egg-loaded individuals, nor did bugs carrying several eggs resist oviposition attempts more often than unloaded ones. Some males were likely to have fertilized the eggs they scraped off their backs. Laboratory results of active egg removal correspond with egg loss in the field, suggesting that egg scraping may explain egg loss in nature. The data indicate a cost of egg carrying to an individual and an evolutionary arms race between oviposition and discarding behavior.     

Characterization of quantitative trait loci (QTLs) in cultivated rice contributing to field resistance to sheath blight (Rhizoctonia solani)

Sheath blight, caused by Rhizoctonia solani, is one of the most important diseases of rice. Despite extensive searches of the rice germ plasm, the major gene(s) which give complete resistance to the fungus have not been identified. However, there is much variation in quantitatively inherited resistance to R. solani, and this type of resistance can offer adequate protection against the pathogen under field conditions. Using 255 F₄ bulked populations from a cross between the susceptible variety Lemont and the resistant variety Teqing, 2 years of field disease evaluation and 113 well-distributed RFLP markers, we identified six quantitative trait loci (QTLs) contributing to resistance to R. solani. These QTLs are located on 6 of the 12 rice chromosomes and collectively explain approximately 60% of the genotypic variation or 47% of the phenotypic variation in the LemontxTeqing cross. One of these resistance QTLs (QSbr4a), which accounted for 6% of the genotypic variation in resistance to R. solani, appeared to be independent of associated morphological traits. The remaining five putative resistance loci (QSbr2a, QSbr3a, QSbr8a, QSbr9a and QSbr12a) all mapped to chromosomal regions also associated with increased plant height, three of which were also associated with QTLs causing later heading. This was consistent with the observation that heading date and plant height accounted for 47% of the genotypic variation in resistance to R. solani in this population. There were also weak associations between resistance to R. solani and leaf width, which were likely due to linkage with a QTL for this trait rather than to a physiological relationship.     

The pathogenicities of Cylindrocarpon tonkinense and Fusarium solani in the rabbit cornea

The pathogenicity of Cylindrocarpon tonkinense in the cornea was evaluated and compared with that of Fusarium solani in rabbits. F. solani was inoculated into the right eyes of 14 rabbits and C. tonkinense was into the left eyes of same rabbits. The corneal lesions of both eyes were examined carefully by slit lamp every day for three weeks and the severity of infections were compared each other. For histopathologic study, several eyes were enucleated periodically. C. tonkinense has a pathogenicity equally strong as F. solani in this inculum size (10⁴ microconidia per cornea) and produced severe infection in rabbit eyes.     

Proximate Mechanisms of Sexual Selection in the Firefly Photinus pyralis (Coleoptera: Lampyridae)

Male competition in courtships of the firefly Photinus pyralis is intense. Morphometric analysis revealed that male size is variable, possibly exhibiting alternative body plans. We examined the outcomes of courtships to determine the proximate mechanisms of selection that may have led to male allometry. Two distinct selective events exist within mate competition: (1) searching and (2) scramble competition. Although many courtships failed, those without rivals were shorter and successful males spent less time in the mate-guarding position than when several males were in competition. Winners outflashed rivals, but flash dialogs occurred at similar frequencies across rival densities, indicating that females require some quantum of information before mating. Female flash preference was examined in choice tests to evaluate female discrimination ability. Females preferred flashes of greater intensity and precedence. This suggests that flash synchronization is a competitive display rather than a cooperative behavior to maintain female responsiveness. Selection for male size was density dependent: females preferred large males in searching, while small males were favored in scrambles. Simulated scrambles showed that small males have superior locomotor abilities, allowing them to reach the female rapidly. Comparison with a species lacking scrambles, P. macdermotti, revealed that selection in P. pyralis is disruptive, targeting traits alternately, and may have led to the evolution of higher allometric ratios in a species with direct male competition. Both male competition and female choice are important determinants of the outcome of P. pyralis courtships.