Susceptibility of the bedbug,Cimex lectularius,to selected insecticides and various treated surfaces

Abstract. Adult bedbugs, Cimex lectularius, were exposed for 24 h (25^oC) to filter paper treated with various dilutions of the technical grade of nine insecticides dissolved in acetone to determine the concentration-response relationships. The order of toxicity, from most to least based on the LC₅₀'s was: dichlorvos, pirimiphos methyl, lambda-cyhalothrin, bendiocarb, permethrin, malathion, carbaryl, tetrachlorvinphos, and fenvalerate. The residual toxicities of commercial formulations of six of the chemicals diluted with water and applied to wood, cardboard, cloth and galvanized metal, were determined by exposing adult bedbugs at 3,7 and 12 weeks after treatment. The formulation of bendiocarb (FICAM® 76% W) had little residual activity on all surfaces at 12 weeks after treatment. The formulation of carbaryl (SEVIN® 21.5% L) was toxic to bedbugs on all surfaces at 12 weeks after treatment, but required high concentrations on wood, cardboard, and cloth. The formulation of pirimiphos methyl (ACTELLIC® 57% EC) had no residual activity on any of the surfaces at 12 weeks after treatment. The formulation of tetrachlorovinphos (RABON® 50% W) had residual activity for 12 weeks on all surfaces except metal. The formulation of permethrin (ATROBAN® 11% EC) had residual activity on only metal and wood while the formulation of lambda-cyhalothrin (KARATE® 13.1% EC) had residual activity 12 weeks on all surfaces.     

Opportunities for female choice in the bed bug Cimex lectularius

Bed bugs are cited as exemplars of sexual conflict because mating can only occur via traumatic insemination. However, past antagonistic coevolution between the sexes does not necessarily preclude current female choice. Here, we investigate opportunities for precopulatory female choice in bed bugs. We examined whether females seek out mating opportunities when they gain the most benefit: when females are virgin and/or have recently fed. But, we found that female mating and feeding status had little effect on female attraction to males and male odor. To determine whether females approach male harborages (home crevices) to seek matings in nature, we investigated where matings occurred among unfamiliar pairs of bed bugs. We found that, despite female attraction to male odor, matings were most likely to take place in the female's harborage rather than the male's harborage. We also examined the effect of feeding on male and female ability to mate. Whereas previous research reported that engorgement impaired female ability to refuse matings, we found that male feeding status had a larger effect on the success of mating encounters than female feeding status. Fed males had poor mating success, suggesting that males may be faced with a trade‐off between mating and feeding.     

Reemergence of the bedbug Cimex lectularius in Seoul, Korea

A healthy 30-yr-old woman carrying an insect that had been caught in her living room visited the International Clinic at Severance Hospital, Seoul, in December 2007. The insect she brought was identified to be a nymph of a bedbug, Cimex lectularius, and her skin rashes looked typical bedbug''s bites. Her apartment was investigated, and a dead body of a bedbug, cast skins, and hatched eggs were found in her rooms and neighbors'' rooms in the same building. She was living in that apartment in Seoul for 9 months since she had moved from New Jersey, USA. We assume that the bedbugs were introduced from abroad, since there had been no report on bedbugs in Seoul for more than 2 decades at least. This is a report of a reemergence of the common bedbug, C. lectularius in Seoul, Korea.     

Water loss and metabolic activity in bed bug eggs (Cimex lectularius)

Few studies have evaluated water loss and respiratory activity of insect eggs, particularly insects that are known to live within indoor environments. The present study quantifies water loss and respiratory activity for the eggs of a re‐emerging indoor pest of human environments Cimex lectularius (L.). Water loss is measured gravimetrically and calculated as a function of chorion permeability. For these studies, bed bug eggs are placed at 0% relative humidity and repeatedly weighed over 48 h. Temperature effects and bed bug strain differences on the standard metabolic rate (SMR) and respiratory quotient are measured using closed system respirometry. The SMR (; mL g^?1 h^?1) is measured for two field strain bed bugs and compared with a laboratory strain held at one temperature (25 °C). The standard metabolic rate is measured for Harlan (laboratory) strain bed bug eggs at six different temperatures (15, 20, 25, 30, 35 and 39 °C). Total water loss is not significantly different between all three strains. However, water loss across the chorion (chorion permeability) is significantly different between the Harlan laboratory strain and the two field collected strains. Standard metabolic rates for Harlan (laboratory) strain bed bug eggs increase with temperatures from 15 to 35 °C but decline at 39 °C. Overall, the Harlan bed bug eggs have the largest standard metabolic rates (0.18 ± 0.05 mL g^?1 h^?1) compared with the Epic Center strain eggs (0.14 ± 0.03 mL g^?1 h^?1) and Richmond strain eggs (0.16 ± 0.04 mL g^?1 h^?1), although this difference is not significant.     

Host association drives genetic divergence in the bed bug,Cimex lectularius

Genetic differentiation may exist among sympatric populations of a species due to long‐term associations with alternative hosts (i.e. host‐associated differentiation). While host‐associated differentiation has been documented in several phytophagus insects, there are far fewer cases known in animal parasites. The bed bug, Cimex lectularius, a wingless insect, represents a potential model organism for elucidating the processes involved in host‐associated differentiation in animal parasites with relatively limited mobility. In conjunction with the expansion of modern humans from Africa into Eurasia, it has been speculated that bed bugs extended their host range from bats to humans in their shared cave domiciles throughout Eurasia. C. lectularius that associate with humans have a cosmopolitan distribution, whereas those associated with bats occur across Europe, often in human‐built structures. We assessed genetic structure and gene flow within and among populations collected in association with each host using mtDNA, microsatellite loci and knock‐down resistance gene variants. Both nuclear and mitochondrial data support a lack of significant contemporary gene flow between host‐specific populations. Within locations human‐associated bed bug populations exhibit limited genetic diversity and elevated levels of inbreeding, likely due to human‐mediated movement, infrequent additional introduction events per infestation, and pest control. In contrast, populations within bat roosts exhibit higher genetic diversity and lower levels of relatedness, suggesting populations are stable with temporal fluctuations due to host dispersal and bug mortality. In concert with previously published evidence of morphological and behavioural differentiation, the genetic data presented here suggest C. lectularius is currently undergoing lineage divergence through host association.     

Temporary feeding inhibition caused by artificial abdominal distension in the bedbug, Cimex lectularius

Abdominal distension of haematophagous insects caused by ingested blood has been recognised as an important contributor to triggering meal termination, feeding inhibition and further susceptibility to host signals. Factors that regulate feeding behaviour of the common bedbug, Cimex lectularius, are poorly understood. By injecting air directly into the body cavity of virgin female C. lectularius we artificially induced abdominal distension without providing chemical cues of the blood meal and without applying gut distension. Body length increased to 138% after feeding and 147% after inflation. The early decline in body volume is similar in blood-fed bugs but after between 8 and 24h became faster in inflated than fed bedbugs. Artificially inflated individuals remained feeding-inhibited at lower abdominal distensions than those that terminate blood ingestion (to ca. 135% initial body length, or up to about 5h). Feeding activity resumed earlier in inflated than blood-fed bugs. These results suggest that artificial abdominal distension has an inhibitory effect on feeding but is not the sole mechanism in preventing further feeding.     

Sex differences in recombination

One of the stronger empirical generalizations to emerge from the study of genetic systems is that achiasmate meiosis, which has evolved 25–30 times, is always restricted to the heterogametic sex in dioecious species, usually the male. Here we collate data on quantitative sex differences in chiasma frequency from 54 species (4 hermaphroditic flatworms, 18 dioecious insects and vertebrates and 32 hermaphroditic plants) to test whether similar trends hold. Though significant sex differences have been observed within many species, only the Liliaceae show a significant sexual dimorphism in chiasma frequency across species, with more crossing over in embryo mother cells than in pollen mother cells; chiasma frequencies are unrelated to sex and gamety in all other higher taxa studied. Further, the magnitude of sexual dimorphism, independent of sign, does not differ among the three main ecological groups (dioecious animals, plants, and hermaphroditic animals), contrary to what would be expected if it reflected sex-specific selection on recombination. These results indicate that the strong trends for achiasmate meiosis do not apply to quantitative sex differences in recombination, and contradict theories of sex-specific costs and benefits. An alternative hypothesis suggests that sex differences may be more-or-less neutral, selection determining only the mean rate of recombination. While male and female chiasma frequencies are more similar than would be expected under complete neutrality, a less absolute form of the hypothesis is more difficult to falsify. In female mice the sex bivalent has more chiasmata for its length than the autosomes, perhaps compensating for the absence of recombination in males. Finally, we observe that chiasma frequencies in males and females are positively correlated across species, validating the use of only one sex in comparative studies of recombination.     

Sex differences in anthropoid mandibular canine lateral enamel formation

Previous research has demonstrated that great ape and macaque males achieve large canine crown sizes primarily through extended canine growth periods. Recent work has suggested, however, that platyrrhine males may achieve larger canine sizes by accelerating rather than prolonging growth. This study tested the hypothesis that the ontogenetic pathway leading to canine sexual dimorphism in catarrhines differs from that of platyrrhines. To test this hypothesis, males and females of several catarrhine genera (Hylobates, Papio, Macaca, Cercopithecus, and Cercocebus) and three platyrrhine genera (Cebus, Ateles, and Callicebus) were compared in the number and spacing of perikymata (enamel growth increments) on their canine crowns. In addition, perikymata periodicities (the number of days of growth perikymata represent) were determined for five genera (Hylobates, Papio, Macaca, Cebus, and Ateles) using previously published as well as original data gathered for this study. The central findings are as follows: 1) males have more perikymata than females for seven of eight genera (in five of the seven, the differences are statistically significant); 2) in general, the greater the degree of sexual dimorphism, the greater the sex difference in male and female perikymata numbers; 3) there is no evidence of a systematic sex difference in primate periodicities; and 4) there is some evidence that sex differences in enamel formation rates may make a minor contribution to canine sexual dimorphism in Papio and Cercopithecus. These findings strongly suggest that in both catarrhines and platyrrhines prolongation of male canine growth is the primary mechanism by which canine crown sexual dimorphism is achieved. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Sex differences in height and sitting height in the Belgian population

Sex differences in growth were studied in a longitudinal study of 39 boys and 31 girls for sitting height. Individual growth patterns were determined by means of Preece Baines model 1. The results showed no significant bias in the fits of height and sitting height in boys and girls. Girls fits were significantly better than those of the boys for both height and sitting height. Univariate analysis by means of Mann-Whitney test showed significant sex differences for all function and biological parameters of height and sitting height excepted for s₁ parameter (the rate constant controlling pubertal velocity). Linear discriminant analysis revealed that the strongest sex differences for the timing and size parameters at adolescent. Peak velocity at adolescent was slightly less discriminating between the two sexes and velocity at take-off showed the least sex difference. These trends were similar for height and sitting height. Decomposition of sex differences in adult size showed that the major contributor to adult the sex differences is the effect of the later onset of the adolescent growth spurt in boys than in girls. Sex differences in adult phenotypes of height and sitting height are to a slightly lesser extent due to the greater adolescent gain in boys while prepubertal sex differences are almost negligible.     

Sex differences in diet and foraging behavior in white-faced capuchins (Cebus capucinus)

I examined sex differences in diet and foraging behavior in two groups of white-faced capuchin monkeys (Cebus capucinus)in a tropical dry forest at Santa Rosa National Park, Costa Rica. I tested three hypotheses: sex differences in diet and foraging behavior are best explained by (1) sexual dimorphism, (2) the energy demands of pregnancy and lactation for females;and (3) avoidance of competition between the sexes. Sexual dimorphism offered the best explanation of sex differences in the diet and foraging behavior of C. capucinus,accurately predicting that males do more strenuous foraging activity, make less use of small foraging supports, and spend more time on or near the ground. Females spent more time foraging than males did but probably obtained a lower protein yield per unit foraging time. Females exploited more small and embedded invertebrates, while males ate more large invertebrates and vertebrate prey. Pregnant and lactating females spent more time resting and less time foraging than other females did, increasing their foraging return by focusing on foods requiring little handling. There was little evidence of competition avoidance between the sexes.     

Sex differences in telomeres and lifespan

Males and females often age at different rates resulting in longevity 'gender gaps', where one sex outlives the other. Why the sexes have different lifespans is an age-old question, still fiercely debated today. One cellular process related to lifespan, which is known to differ according to sex, is the rate at which the protective telomere chromosome caps are lost. In humans, men have shorter lifespans and greater telomere shortening. This has led to speculation in the medical literature that sex-specific telomere shortening is one cause of sex-specific mortality. However, telomere shortening may be a cause for and/or a consequence of the processes that govern survival, and to infer general principles from single-taxon studies may be misleading. Here, we review recent work on telomeres in a variety of animal taxa, including those with reverse sexual lifespan dimorphism (i.e., where males live longer), to establish whether sex-specific survival is generally associated with sex differences in telomere dynamics. By doing this, we attempt to tease apart the potential underlying causes for sex differences in telomere lengths in humans and highlight targets for future research across all taxa.     

Sex ratios, size distributions, and sexual dimorphism in the dioecious tree Ilex aquifolium (Aquifoliaceae)

Sex ratio and sexual dimorphism in physiology and growth were studied in the dioecious tree Ilex aquifolium at two localities in northern Spain. Genet sex ratio was significantly male biased in one locality but not in the other. However, ramet and flowering ramet sex ratios were male biased at both study sites. Males had significantly thicker main trunks than females in one locality and produced more ramets in the other. Growth rate, estimated from mean width of annual rings, did not differ between localities, but males produced wider rings than females at both sites. Mean annual growth rates over the last 10, 20, and 30 yr were significantly higher for males. Measurements of chlorophyll fluorescence indicated that the efficiency of photosynthesis of leaves on nonfruiting branches of females was higher than for leaves on branches of male plants under low-light conditions, though not under saturating-light conditions. Efficiency of photosynthesis was significantly lower on fruiting branches of female plants than on nonfruiting branches. We discuss whether the observed between-sex differences are attributable to the higher cost of reproduction in females and/or to pollen competition.     

Sex differences in growth rates of Yellow-legged Gull Larus michahellis chicks

Capsule: Chick growth rates was sex-dependent in an Atlantic Yellow-legged Gull Larus michahellis population.

Aims: To describe the growth rate of Yellow-legged Gull chicks and sex-associated variations, and obtain a discriminant function to sex them using morphological data.

Methods: Fifty-two Yellow-legged Gull chicks from a colony in northern Iberia were measured for body mass, head and bill length, tarsus length and three other bill-length associated variables, from the hatching date up to the age of 36 days. Birds were sexed using DNA analysis.

Results: Using logistic models, chick growth rates was observed to be similar between the sexes, while the asymptote was higher among males for the majority of the variables. Discriminant analyses showed that the variable head+bill was very reliable to predict the sex of >80% of chicks at an early developmental stage, and 100% of chicks if combined with tarsus length and two more bill-length associated variables at the age of 35 days.

Conclusions: This is the first study using a discriminant analysis to sex Yellow-legged Gull chicks, and also the first to describe the growth function for the species. The growth rate varied between sexes because males showed higher asymptote values within the growth function.     

Sex differences in behaviour as an indirect consequence of mating system

A considerable literature has been devoted to documenting differences between the sexes. However, relatively little attention has hitherto been directed towards those differences that arise as an indirect consequence of mating system even though they can have profound implications for the daily lives of the animals involved. In this review we focus on differences in the non-reproductive behaviour of fish and relate these to sexual dimorphism in size and morphology, and to variance in fitness between the sexes. In line with our expectation, differences in distributional ecology, schooling, aggression, predator avoidance and foraging are exaggerated in sexually dimorphic species and polygamous mating systems. Nonetheless, the behaviour of males and females may also differ in sexually monomorphic and monogamous species. We conclude by highlighting promising directions for further research.     

Seasonal and life‐phase related differences in growth in Scarus ferrugineus on a southern Red Sea fringing reef

Temporal trends in growth of the rusty parrotfish Scarus ferrugineus were studied on a southern Red Sea fringing reef that experiences seasonal changes in environmental conditions and benthic algal resources. Length increment data from tagging and recapture were compared among periods and sexes and modelled using GROTAG, a von Bertalanffy growth model. The growth pattern of S. ferrugineus was highly seasonal with a maximum occurring between April and June and a minimum between December and March. Body condition followed the seasonal variation in growth, increasing from April to June and decreasing from December to March. The season of maximum growth coincided with high irradiation, temperature increases and peak abundance of the primary food source, the epilithic algal community. There was a decline in growth rate during summer (July to October) associated with a combination of extreme temperatures and lowered food availability. There were strong sexual size dimorphism (SSD) and life‐history traits. Terminal‐phase (TP) males achieved larger asymptotic lengths than initial‐phase individuals (IP) (L_∞ 34·55 v. 25·12 cm) with growth coefficients (K) of 0·26 and 0·38. The TPs were growing four times as fast as IPs of similar size. Three individuals changed from IP to TP while at liberty and grew eight times faster than IPs of similar size, suggesting that sex change in S. ferrugineus is accompanied by a surge in growth rate. The SSD in S. ferrugineus thus coincided with fast growth that started during sex change and continued into the TP. Faster growth during sex change suggests that the cost associated with sex change is limited.     

Sex differences in sexual partner acquisition, retention, and harassment during female homosexual consortships in Japanese macaques

Female Japanese macaques (Macaca fuscata) in certain populations are unusual in that they exhibit male-typical patterns of mounting behavior and sexual-partner preference. The goal of this study was to determine whether female Japanese macaques, from one such population, employ male-typical behavioral tactics to disrupt existing homosexual consortships, as well as to acquire and retain same-sex sexual partners. "Harassment" of homosexual consortships occurred when a sexually motivated, third-party male or female interrupted a consorting female couple by displacing or aggressing them. Sexual harassment was a male-typical strategy for disrupting existing homosexual consortships, but was rarely performed by females. "Intrusions" occurred when a male or female competitor attempted to acquire exclusive access to a female engaged in a homosexual consortship by targeting that female as the focus of competition and her partner as his/her competitor. "Sexual coercion" occurred when one individual alternately sexually solicited and aggressed another individual as part of the same behavioral sequence during an intrusion. Males employed consortship intrusions and sexual coercion when they attempted to acquire female sexual partners that were already engaged in homosexual consortships, but females rarely did so. However, females did employ male-typical patterns of aggressive competition and sexual coercion to retain same-sex sexual partners when confronted with male competitors' attempts to usurp those partners. These results indicate that female sexual activity during homosexual consortships is not uniformly "masculine" in expression, but rather is a mixture of male- and female-typical behaviors.