Sehirus Cinctus Research Articles

Pre- and post-hatch trophic egg production in the subsocial burrower bug, Canthophorus niveimarginatus (Heteroptera: Cydnidae)

In recent years, three terrestrial bugs, Adomerus triguttulus and Sehirus cinctus (Cydnidae) and the closely related Parastrachia japonensis (Parastrachiidae), have been the focus of several fascinating studies because of the remarkable, extensive parental care they were found to display. This care includes egg and nymph guarding, production of trophic eggs, unfertilized, low cost eggs that are used as food by newly hatched nymphs, and progressive provisioning of the host seed. In this study, we have investigated yet a third related Asian cydnid, Canthophorus niveimarginatus, with regard to the possible occurrence of some or all of these complex traits in order to assess how widespread these maternal investment patterns are in this group of insects and to better understand the implications of their manifestations from an evolutionary context. Manipulative experiments were carried out in the lab to determine whether females provision nests. Observational and egg removal studies were carried out to determine whether trophic eggs are produced, and, if they are, their possible impact on nymphal success. The findings revealed that C. niveimarginatus does, in fact, progressively provision young, and this species also displays all of the other behaviors associated with extended parental care in subsocial insects. Moreover, unlike the other two related species, which place trophic eggs on the surface of the original egg mass, C. niveimarginatus produces both pre- and post-hatch trophic eggs. Nymphs deprived of access to post-hatch trophic eggs had significantly lower body weight and survival rate than those that fed on them. To our knowledge, this is the first time the production of both pre- and post-hatch trophic eggs has been demonstrated in insects outside the Hymenoptera. In this paper, we qualitatively and quantitatively demonstrate the provisioning behavior and patterns of trophic egg production in C. niveimarginatus. When and how trophic eggs are produced and delivered to young should have important correlations with the ecological and life history constraints under which a species has evolved. Thus, we also discuss the possible ecological and life history factors that favor the evolution of post-hatch trophic eggs.

Maternal food provisioning in relation to condition-dependent offspring odours in burrower bugs (Sehirus cinctus)

The sensory modalities used for communication among family members have at least partly evolved within an organism's pre-existing sensory context. Given the well-known general importance of chemical communication in insects, we hypothesized in sub-social insects with parental care that chemical signals emitted by larvae to influence parental care (i.e. solicitation pheromones) would have evolved. To test this hypothesis, we performed an experiment in the burrower bug Sehirus cinctus (Hemiptera: Cydnidae) where nymphs were hand-reared under high- or low-food conditions. These hand-reared clutches were used as a source of volatiles. The volatiles were collected for chemical analysis and delivered to caring mothers to quantify their behavioural response. As predicted, mothers exposed to volatiles from nymphs in poor condition provisioned significantly more food than those exposed to air (controls) or volatiles from high-condition nymphs. Chemical analysis revealed that nymphs emitted a blend of eight compounds of which alpha-pinene and camphene showed the strongest relationship with food treatment. Exposure to pure synthetic alpha-pinene and camphene did not affect maternal provisioning, however, suggesting that the functional significance of alpha-pinene and/or camphene may occur in a blend with other compounds. This study shows a clear effect of condition-dependent offspring odours on maternal food provisioning and identifies, for the first time, candidate compounds for a potential chemical offspring begging signal.

Offspring chemical cues affect maternal food provisioning in burrower bugs, Sehirus cinctus

Female burrower bugs (Sehirus cinctus, Hemiptera: Cydnidae) show extended care for their offspring. They guard their clutch and feed the hatched nymphs up to the third larval instar. Previous research indicated that nymphs partly regulate maternal food provisioning, but how nymphs accomplish this is unknown. We tested the hypothesis that nymphs solicit maternal provisioning by condition-dependent chemical signalling and we postulated the existence of a solicitation pheromone. Clutches of 30 nymphs were handreared in either low- or high-food conditions. After moult to second instar, cuticular compounds were extracted in hexane. An independent set of test mothers caring for offspring were subsequently exposed to extracts of nymphs from either the low- or the high-food treatment. Two control groups were also involved, one exposed to the solvent hexane and one with no treatment. As predicted for a solicitation pheromone, test mothers exposed to extracts from nymphs reared under low food provisioned more than those exposed to extracts from nymphs reared under high-food treatment. Contrary to our expectation, however, nymph extracts had an overall inhibiting effect on maternal provisioning. The effects of extract exposure on maternal provisioning were short-lasting, suggesting that the critical cues may be volatile. Our results suggest complex chemical communication in burrower bug families for the short-term regulation of maternal provisioning, potentially involving both provisioning-releasing solicitation pheromones and inhibiting chemical cues.

Insights into the costs of complex maternal care behavior in the burrower bug (Sehirus cinctus)

The evolution of life history characters, including parental care behaviors, depends on costs and benefits. When offspring can influence parental behaviors, parent-offspring conflict over parental care can occur, but only if these parental behaviors are costly. Mother burrower bugs (Sehirus cinctus) exhibit extended and complex care of offspring. Mothers guard eggs until hatching and then attend and provision offspring for approximately 2 weeks after hatching. Using four experimental treatments, we attempted to identify the costs associated with specific components of these behaviors. Under laboratory conditions, egg guarding increases inter-clutch interval, but provisioning does not appear to be very costly. We discuss additional ecological factors that may be important in mediating provisioning costs under natural conditions. Through analysis of individual maternal performance, we find no evidence for trade-offs between successive clutches. These data suggest that variation in overall condition may obscure variation in allocation strategies.

On the social structure of offspring rearing in the burrower bug, Sehirus cinctus (Hemiptera: Cydnidae)

Maternal-offspring interactions are important in a variety of animals. Understanding the evolution of these interactions requires that we also study the broader social context in which they occur. To date, behavioral studies on burrower bugs, Sehirus cinctus, have focused exclusively on interactions between mothers and offspring. Here we ask whether these interactions occur in a social context that extends beyond the family unit of a mother and her own genetic offspring. Such social structure can arise from behaviors that occur before eggs are laid, or from actions of individuals that occur post-hatching. We present field data showing that lay sites of mothers are spatially aggregated on a scale that would lead to behavioral interactions among families. Microsatellite markers suggest neighboring mothers are unrelated. Laboratory experiments do not support the hypothesis that spatial aggregation results from a direct attraction of females to one another. Other laboratory studies reported here indicate that, after hatching, unrelated clutches sometimes join together to form multifamily groups. Experiments reveal that mothers are not necessary for these joining events to occur. In sum, these data suggest that both mothers and offspring play active, but different, roles in generating the social environment in which offspring rearing occurs.

An Analysis of Single Clutch Paternity in the Burrower Bug Sehirus cinctus Using Microsatellites

Recent studies of the burrower bug, Sehirus cinctus, have examined the genetic basis of parental care. An understanding of the burrower bug mating system, and the subsequent pattern of offspring relatedness that this system generates, is critical to further interpret genetic data. To this end, we developed three consistently amplifiable highly polymorphic microsatellite loci and used them to determine genotypic patterns at the level of both the population and the single clutch. We found that all clutches were sired by single males. Further, we find no evidence for inbreeding. We hypothesize that single paternity within a clutch may play an important role in reducing the potential for sibling rivalry, by increasing the relatedness among clutchmates.

Burrower Bugs (Heteroptera: Cydnidae) in Peanut: Seasonal Species Abundance, Tillage Effects, Grade Reduction Effects, Insecticide Efficacy, and Management

Pitfall traps placed in South Carolina peanut, Arachis hypogaea (L.), fields collected three species of burrower bugs (Cydnidae): Cyrtomenus ciliatus (Palisot de Beauvois), Sehirus cinctus cinctus (Palisot de Beauvois), and Pangaeus bilineatus (Say). Cyrtomenus ciliatus was rarely collected. Sehirus cinctus produced a nymphal cohort in peanut during May and June, probably because of abundant henbit seeds, Lamium amplexicaule L., in strip-till production systems. No S. cinctus were present during peanut pod formation. Pangaeus bilineatus was the most abundant species collected and the only species associated with peanut kernel feeding injury. Overwintering P. bilineatus adults were present in a conservation tillage peanut field before planting and two to three subsequent generations were observed. Few nymphs were collected until the R6 (full seed) growth stage. Tillage and choice of cover crop affected P. bilineatus populations. Peanuts strip-tilled into corn or wheat residue had greater P. bilineatus populations and kernel-feeding than conventional tillage or strip-tillage into rye residue. Fall tillage before planting a wheat cover crop also reduced burrower bug feeding on peanut. At-pegging (early July) granular chlorpyrifos treatments were most consistent in suppressing kernel feeding. Kernels fed on by P. bilineatus were on average 10% lighter than unfed on kernels. Pangaeus bilineatus feeding reduced peanut grade by reducing individual kernel weight, and increasing the percentage damaged kernels. Each 10% increase in kernels fed on by P. bilineatus was associated with a 1.7% decrease in total sound mature kernels, and kernel feeding levels above 30% increase the risk of damaged kernel grade penalties.

Parent-offspring coadaptation and the dual genetic control of maternal care.

In many animal species, the amount of care provided by parents is determined through a complex interaction of offspring signals and responses by parents to those signals. As predicted by honest signaling theory, we show that in the burrower bug, Sehirus cinctus, maternal provisioning responds to experimental manipulations of offspring condition. Despite this predicted environmental influence, we find evidence from two cross-foster experiments that variation in maternal care also stems from two distinct genetic sources: variation among offspring in their ability to elicit care and variation among parents in their response to offspring signals. Furthermore, as predicted by maternal-offspring coadaptation theory, offspring signaling is negatively genetically correlated with maternal provisioning.

Precocene II modifies maternal responsiveness in the burrower bug, Sehirus cinctus (Heteroptera)

Abstract. The anti‐Juvenile Hormone agent precocene II was used to investigate the relationship of corpora allata activity to subsocial behaviour in a burrower bug Sehirus cinctus Palisot (Heteroptera: Cydnidae). Egg‐brooding females treated with a range of dosages of precocene II exhibited reliably depressed maternal defensive behaviour when treated with at least 70 μg of precocene II, but attraction to eggs was only depressed at higher dosages. This effect was not due to precocene II toxicity, as demonstrated by the prevention of depression effects through simultaneous treatments of precocene II and the Juvenile Hormone analogue methoprene. Methoprene, however, failed to reinstate maternal responsiveness in maternally depressed females that had been previously treated with precocene II. This study provides the first clear evidence that insect parental behaviour can be modified by treatment with anti‐Juvenile Hormone agents, and suggests that the role of the corpora allata in governing care in S. cinctus is different from that of other maternal insects, such as earwigs.

Chemistry and Defensive Efficacy of Secretion of Burrowing Bug (Sehirus cinctus cinctus)

Adult Sehirus cinctus cinctus emit a volatile secretion from their metathoracic scent glands when tactually stimulated. We identified the volatile components by gas chromatography, high-performance liquid chromatography, and mass spectrometry. The secretion of both sexes contained (1R)-(+)-α-pinene, (1S)-(–)-β-pinene, β-myrcene, (R)-(+)-limonene, and α-terpinolene. Two additional compounds were found in only female secretions: (E)-2-hexenyl acetate and (E)-2-octenal. We also tested the defensive capability of this insect by offering it to various predators. Anoles, starlings, and a killdeer rejected S. c. cinctus after an initial sampling. These findings suggest that the secretion plays a defensive role.

Factors influencing maternal behaviour in a burrower bug,Sehirus cinctus(Heteroptera: Cydnidae)

Female burrower bugs,Sehirus cinctus(Cydnidae), brood and provision their young. This study provides an integrative approach to insect parental behaviour by examining the influence of maternal experience on the maintenance and termination of maternal care. Intensity of care (maternal responsivity) was determined by assaying a subject's response to tactile disturbance and by measuring time spent in proximity to young. First-brood mothers were highly responsive until 3 days after their eggs hatched. Second-brood mothers, however, were only responsive until 1–2 days post-hatching. This effect was associated with differences in age and parity, but not experience, because second-brood females prevented from caring for their first group of eggs did not differ from females with previous maternal experience. To examine cues surrounding the termination of care, cross-fostering techniques were used to move the time of hatching such that it occurred either several days early (truncated brooding) or not at all (extended brooding). Females experiencing a ‘premature’ hatch showed immediate declines in responsivity following hatching. Extended brooders, which guarded viable but ‘unhatching’ eggs, remained highly responsive for 6 days after their own eggs would have hatched before terminating care. These findings suggest that internal processes and external cues interact to ensure that maternal care is of appropriate duration. 1997 The Association for the Study of Animal Behaviour

Concaveation and maintenance of maternal behavior in a burrower bug (Sehirus cinctus): a comparative perspective.

This study investigates 2 patterns of maternal behavior typical of mammals, using a heteropteran insect as the study animal. Sehirus cinctus, a burrower bug (Heteroptera: Cydnidae), exhibits relatively well-developed maternal behavior that includes guarding eggs and provisioning offspring. Mothers remained maternally responsive to stimulus eggs for 24-48 hr following removal of their own eggs, but the response grew weaker with longer separation times. A proportion of nulliparous females also exhibited maternal responsiveness when presented with stimulus eggs. Males, however, never responded parentally to eggs. The results of this study highlight similarities in general female responsiveness to stimulus young and differences in male responsiveness to stimulus young among certain invertebrates and vertebrates.

Concaveation and maintenance of maternal behavior in a burrower bug (Sehirus cinctus): A comparative perspective.

Concaveation and maintenance of maternal behavior in a burrower bug (Sehirus cinctus): A comparative perspective.

Do maternal burrower bugs, Sehirus cinctus Palisot (Heteroptera: Cydnidae), use spatial and chemical cues for egg discrimination?

Female Sehirus cinctus Palisot (Heteroptera: Cydnidae) dig shallow burrows in which they guard their eggs and provision young nymphs. Because maternal females often oviposit in close proximity to other females, they must discriminate between their own and strange burrows to avoid investing in unrelated young. Observations that foraging females adhere to precise "trails" indicate that maternal females may use pheromonal cues to locate their burrows. Egg-discrimination trials indicate that maternal females unfamiliar with a test arena do not distinguish between their own eggs and similar strange eggs. However, when maternal females were allowed 24 h experience with the test arena, they chose to guard eggs located where they had previously brooded, even if the eggs were not their own. In addition, maternal females preferred recently brooded eggs over eggs that had been isolated for 24 h. These results indicate that foraging females use spatial and chemical cues to discriminate their own eggs from strange eggs.

Life History and Laboratory Rearing of Sehirus cinctus cinctus (Hemiptera: Cydnidae), with Descriptions of Immature Stages1

The life history of the burrower bug Sehirus cinctus cinctus (Palisot de Beauvois) was studied in Illinois, and the immature stages were described. The bug was also reared from egg to adult under laboratory conditions, and precopulatory behavior, and maternal care of eggs and young instars, were observed. The female occasionally provided her 1st instars with the seeds. Adults of this univoltine subspecies overwinter in soil associated with their mint host plant, Lamium purpureum Linn. They become active in early April and reproduce shortly thereafter. The female lays her eggs in a loose cluster in a chamber in the soil and guards them during incubation. The 1st instars are highly gregarious and often cluster around and on the female. Older nymphs are also gregarious but decreasingly so as they mature, and usually leave the chamber during the second stadium. Nymphs and adults fed on seeds of L. purpureum. On seeds of L. purpureum, and at 23.9 ± 1.1°C and 16L:8D, total developmental time averaged 53.21 days. The incubation period averaged 10.21 days. Durations of the five nymphal stadia averaged 5.29, 6.26, 6.53, 9.70, and 15.22 days, respectively.

Some observations on Sehirus cinctus (Palisot de Beauvois) (Heteroptera: Cydnidae)

The feeding habits of Sehirus cinctus were studied using the hedge nettle Stachys palustris. Descriptions and measurements of egg clusters and the five nymphal instars are given.