Detection of cockroach faeces: consumption of fluorescent bait and production of UV‐light‐detectable faeces from German cockroach,Blattella germanica

Cockroaches have long been recognized as a major source of allergens in the human environment. As some allergens produced by cockroaches are accumulated within their tiny faeces and may persist unseen in the environment, development of a reliable method for monitoring cockroach faeces distribution and abundance is crucial. Our aim was to explore the rate of consumption of fluorescent bait and defecation of UV‐light‐detectable fluorescent faeces from Blattella germanica (L.) (Blattodea: Ectobiidae) as a prerequisite for the establishment of faeces monitoring in the field. Laboratory experiments revealed that (1) the fluorescent bait was accepted by cockroaches as a food source and faeces produced after its consumption were fluorescent as well; (2) there was a positive relationship between the fluorescent bait consumed and production of fluorescent faeces; (3) single and brief consumption of fluorescent bait led to continuous fluorescent faeces production, giving cockroaches enough time (ca. 27 h) to deposit fluorescent faeces in an entire area of cockroach activity as well as in shelters. The amount of fluorescent bait consumed and the amount of fluorescent faeces produced was nevertheless different among males, non‐gravid females, and gravid females. We subsequently validated the new fluorescent faeces‐based monitoring technique in a semi‐field experiment with human observers, which revealed that fluorescent faeces were reliably identified and distinguished from environmental dirt when illuminated with a UV flashlight. We further discuss the biological perspectives of our findings and recommendations for practical use.     

Toxicity, sublethal effects, and performance of sulfluramid against the German cockroach (Dictyoptera: Blattellidae)

Topical and oral toxicity of sulfluramid (N-ethyl perfluorooctane sulfonamide) were determined for the German cockroach, Blattella germanica (L.). The topical LD50 of sulfluramid was 175.6 micrograms/g for adult males, 117.8 micrograms/g for adult females, and 122.3 micrograms/g for gravid adult females. Ingestion increased toxicity approximately 1.4 times for adult male B. germanica. Twenty-four hours after topical treatment with 20 micrograms/insect sulfluramid, the percentage of female cockroaches that dropped their oothecae increased approximately 50% compared with controls treated with acetone. Sulfluramid also decreased oothecal hatch of both dropped and retained oothecae. Approximately 90% of oothecae from untreated females hatches, whereas less than 20% hatched from females treated with 20 micrograms/insect. Mean time for oothecal hatch increased linearly with increasing sulfluramid concentration. In arena studies in Ebeling choice boxes, LT50's ranged between approximately 2.3 and 3.9 d for a 0.331 mg/cm2 deposit and a 1.5% bait, respectively. Higher concentrations of sulfluramid were more repellent in both bait and residual formulations. Performance index values indicated excellent potential field efficacy. Field trials with 1.0 and 1.5% (AI) baits showed up to a 71.3% reduction in cockroach numbers. Baits controlled cockroaches throughout the 12-wk test.     

Female German cockroaches join conspecific groups based on the incidence of auditory cues

Insects deciding whether to approach and join a group of conspecifics may utilize olfactory and auditory signals, or cues, from that group as indicators of its size or the suitability of its shelter. Here we show (1) that German cockroaches, Blattella germanica L. (Dictyoptera: Blattellidae), in groups wing‐fan; (2) that the incidence of wing‐fanning (WF) increases proportionately to group size; and (3) that gravid females utilize auditory cues associated with WF behaviour when they decide whether or not to enter a shelter. In binary choice arena bioassays, proportionately more gravid females avoided shelters associated with play‐back of high‐incidence male‐ or female‐produced WF sound, indicating a high‐density group of conspecifics, but sought shelters associated with play‐back of low‐incidence WF sound, indicating a low‐density group of conspecifics. These auditory cues seem to convey information on group size or density, avoid sensory fatigue in enclosed environments, and allow sonotactic orientation to the group's location.     

Spatio‐temporal analysis of the role of faecal depositions in aggregation behaviour of the triatomine Rhodnius prolixus

Several triatomine species aggregate over conspecific faeces. In some domestic species, this behaviour might help individuals to find their refuges because faeces are usually deposited around such places. In the present study, the defaecation behaviour of the triatomine bug Rhodnius prolixus Stål (Heteroptera: Reduviidae) is described in detail, including the temporal pattern of aggregation of nymphs with different nutritional status to faeces of different post‐deposition times. First, using an experimental arena, the spatial distribution of faecal deposition spots released by nymphs, in relation to the position of a refuge, is recorded. The results show that a high density of faeces is deposited inside the refuge, and few and distant spots, in relation to the position of the refuge, are dropped outside. Second, whether the aggregation behaviour of nymphs is altered by the time elapsed from deposition of the faeces, and by the nutritional status of the insects, is determined. The post‐deposition time of the faeces strongly modulates the aggregation response of the insects. Differences in aggregation between fed and unfed insects are only marginally significant; however, different temporal windows of aggregation according to the post‐deposition times of the faeces are demonstrated between bugs of different nutritional status. The results are discussed with respect to the relevance of the aggregation signal in relation to the characteristics of the natural refuges used by R. prolixus.     

Female House Mice do not Differ in Their Exploratory Behaviour from Males

Dispersal is an important ecological trait affecting genetic variation and dynamics of populations. Hence, the exploratory behaviour prior to actual dispersal may be crucial for potentially dispersing individuals. In mammals, females are traditionally seen as the more philopatric sex and dispersal as male‐biased behaviour, and so behavioural strategies related to the exploration of novel resources should be differentially expressed in males and females. In addition, due to sexual selection exploratory strategies may be expected to vary according to females’ reproductive phase. We employed a standard open‐field test as an approximation of the first phase of dispersal, using adult house mice representing two subspecies, M. m. musculus and M. m. domesticus. We tested the prediction that exploration of neutral area varies in females during different phases of the oestrus cycle and is different between both sexes and subspecies. We expected to find higher exploration in males, as the more dispersing sex and less pronounced subspecies‐specific differences in females than in males. We found no significant effect of the oestrous phase on any of the parameters of the exploratory behaviour measured. Sexual dimorphism was found only in latency to enter the arena in M. m. domesticus where females hesitated longer to enter a new area than males. Significant subspecies‐specific differences were found in three of four tested exploration parameters, so we conclude that females of both subspecies follow similar strategies to those displayed by males. Musculus mice show shorter latency to enter a new area, but once inside, domesticus mice explore the arena significantly longer, with less frequent retreats to a shelter. Our results thus highlight that the role of female dispersal in interdemic gene flow should not be neglected.     

Toxicity of several insecticide formulations against adult German cockroaches (Dictyoptera: Blattellidae)

Toxicity of bendiocarb, chlorpyrifos, cyfluthrin, cypermethrin, fenvalerate, hydramethylnon, malathion, propetamphos, propoxur, and pyrethrins against the adult German cockroaches, Blattella germanica (L.), was investigated. At LD50, cyfluthrin was the most toxic insecticide to adult males (0.53 microgram/g), adult females (1.2 micrograms/g), and gravid females (0.85 microgram/g). Malathion was the least toxic insecticide to adult males (464.83 micrograms/g), adult females (335.83 micrograms/g), and gravid females (275.90 micrograms/g). Males and gravid females were generally more sensitive than nongravid females to the insecticides that we tested. In tests with malathion, however, males were more tolerant. The order of toxicity of the insecticide classes varied among the stages of adult German cockroaches. The order of toxicity for males and nongravid females was pyrethroids greater than pyrethrins = organophosphates (except malathion) greater than carbamates = amidinohydrazone. The order of toxicity for gravid females was pyrethroids greater than pyrethrins = organophosphates (except malathion) greater than carbamates greater than amidinohydrazone. These differences in toxicity suggest that sex differences should be considered when determining insecticide toxicity for German cockroaches.     

Larviposition, Host Cues, and Planidial Behavior in the Sound-Locating Parasitoid Fly Homotrixa alleni (Diptera: Tachinidae)

Some groups of tachinid flies deposit mobile first-instar larvae (or planidia) on or near their host. Flies within one such group, the tribe Ormiini, parasitize singing species of ensiferan Orthoptera and use sound for long distance host location. However, what induces tachinids to larviposit and whether planidia use any cues actively to locate their host remains poorly known. This paper examines the larviposition and planidial behavior of the ormiine Homotrixa alleni in relation to its bushcricket host, Sciarasaga quadrata. Sound alone was sufficient to elicit larviposition in gravid female H. alleni, where females arriving at an arena placed over a speaker broadcasting host song deposited an equal number of planidia in the presence or absence of a silent S. quadrata. Flies were observed to larviposit by forcibly expelling planidia up to 6 cm in a forward direction from the fly, with less than half of the trials with a host present resulting in physical contact between the host and the fly. In the host's absence, flies walked around the arena significantly more often, remained on the arena for the experimental duration (10 min), and changed orientation frequently. In the host's presence, flies generally maintained a position facing the host, stayed in the quadrant of first approach, and typically flew off the arena within 2 min of arrival. When the oncoming fly approached a forward facing host, more planidia were found in the arena's center (i.e., closer to the host) than in the no-host or rearward-facing host treatment. Planidia experimentally placed on a circular arena averaged 1 cm of movement in 15 min but none of the following cues–host song, host song with song-vibration transmission, a silent host, and a silent host with host movement-vibration transmission–significantly affected the direction or distance planidia traveled. At 20 ± 1°C, over half of the planidia died within 1 h and all died within 2 h of deposition. The significance of these results in relation to reproductive strategies and parasitism is discussed.     

Host location in Oomyzus gallerucae (Hymenoptera: Eulophidae), an egg parasitoid of the elm leaf beetle Xanthogaleruca luteola (Coleoptera: Chrysomelidae)

Eggs of the elm leaf beetle Xanthogaleruca luteola are often heavily attacked by the chalcidoid wasp Oomyzus gallerucae. We studied the chemical signals mediating interactions between the egg parasitoid, its host, and the plant Ulmus campestris. Olfactometer bioassays with O. gallerucae showed that volatiles of the host-plant complex attract the parasitoid. In order to determine the source of attractive volatiles within this host-plant-complex, we tested separately the effect of odours of eggs, gravid elm leaf beetle females, faeces of the beetles and elm twigs (with undamaged leaves and leaves damaged either mechanically or by feeding of the beetles). Odours of faeces of the elm leaf beetle were attractive, whereas neither volatiles from eggs nor from gravid females acted as attractants. Volatiles from undamaged or damaged plants did not elicit a positive reaction in O. gallerucae, whereas volatiles from feeding-damaged plants onto which host eggs had been deposited were attractive. This latter result suggests that it is not feeding but deposition of host eggs onto elm leaves that induces the production of plant volatiles attractive to the egg parasitoid. Investigations of the search patterns of O. gallerucae within the habitat by laboratory bioassays revealed that the egg parasitoid encounters host eggs by chance. Contact kairomones from faeces were demonstrated to be important in microhabitat acceptance, while contact kairomones isolated from the host eggs are relevant for host recognition. Received: 12 February 1997 / Accepted: 29 April 1997     

Trail-following behavior in the German cockroach (Dictyoptera: Blattellidae)

The trail-following behavior of the German cockroach, Blattella germanica (L.), was evaluated by comparing the distance between cockroach movement paths and preapplied "trails" of fecal extract. For each cockroach group tested (adult males, females, gravid females, and late instars), the mean perpendicular distance of the cockroach from the trail was significantly less than the distance from a control trail. The results indicated that the German cockroaches did exhibit trail-following behavior. Trail- following accuracy varied among the cockroach groups. The mean distance from the fecal trail ranged from 18.45 to 110.05 cm with adult males < or = adult females < or = late instars < gravid females. Very dilute fecal extract could still induce trail-following behavior in adult male cockroaches. A 5.6% concentration of fecal extract in methanol was able to induce trail-following behavior in 50% of the cockroaches. Although German cockroaches have demonstrated trail-following behavior, fecal trails are still not thought to be actively deposited. Rather, the passive distribution of fecal material within the home range results in the accumulation of trails along frequently traveled routes (i.e., between resources and the cockroach harborage).     

Growth, maturation and survival of frogs Rana temporaria L.

A total of 1560 breeding frogs were collected in three consecutive years at sites in the west of Ireland. Alt were weighed and measured and the ages of 702 individuals were determined by skeletochronology. The length-weight relationship differed between gravid females, spent females and males, with the gravid females showing the largest weight gain for any increase in length. The majority of males bred for the first time at two years, but most females delayed maturity until they were a year older. While the two-year olds were of similar size, the females subsequently grew at a faster rate and achieved larger maximal sizes than the males. However, both sexes exhibited a decelerating growth rate with age. There was no apparent difference between the sexes in post-maturation survival, which was estimated to be about 50% annually. The oldest frogs were seven years old.     

Reproductive biology of the German cockroach,Blattella germanica: Juvenile hormone as a pleiotropic master regulator

Juvenile hormone (JH) exerts major pleiotropic effects on cockroach development and reproduction. The production of JH by the corpora allata (CA) in the adult female German cockroach, Blattella germanica, is dependent upon and modulated by both internal and environmental stimuli. Mating, intake of high-quality food, social interactions, and the presence of vitellogenic ovaries facilitate JH synthesis. Conversely, starvation, deficient diets, enforced virginity, isolation, and a pre- or post-vitellogenic ovary cause the CA to produce less JH. Sensory stimulation of the genital vestibulum by the ootheca also inhibits the CA via signals that ascend the ventral nerve cord. All these stimulatory and inhibitory signals are integrated by the brain, and a preponderance of favorable signals results in a graded lifting of brain inhibition, permitting the synthesis and release of JH. The effects of inhibitory signals on JH biosynthesis can be lifted experimentally by severing nervous connections between the brain and the CA. Such an operation accelerates activation of the CA. Besides controlling gonadal maturation in females, JH concurrently regulates the production of sexual signals, including both attractant- and courtship-eliciting pheromones, and the behavioral expression of calling (pheromone release) and sexual receptivity. Although JH is required for the expression of copulatory readiness in female B. germanica, it appears that signals associated with copulation (spermatophore, sperm, accessory secretions) can inhibit this behavioral state even when titers of JH are permissive for receptivity. These observations suggest that JH might regulate sexual receptivity in females indirectly through other directives. In males, JH accelerates not only the onset of sexual readiness but also synthesis of accessory reproductive products. Lastly, we present a novel cockroach control strategy that is based on the intimate association between food intake and rising JH titers in B. germanica females. JH analogs cause abortion of fertile oothecae in gravid females. In turn, rising JH titers and vitellogenic oocytes induce feeding in females. With strategic placement of insecticidal baits and JH analogs, gravid females, which normally feed little and are difficult to control, can thus be effectively targeted for elimination. Arch. Insect Biochem. Physiol. 35:405–426, 1997. © 1997 Wiley-Liss, Inc.     

Comparison of several traps for catching German cockroaches (Dictyoptera: Blattellidae) under laboratory conditions

German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), catch by five types of traps and modifications of each, were tested under controlled laboratory conditions. Cockroach catch differed significantly among traps. Lo-line trap caught the greatest number of cockroaches in the test arena for each size class (23% small nymphs, 39% of gravid females, and 60% of other size classes in the experimental arena). Jar traps caught the least number of cockroaches in the test arena for each size class (range, 7-23% of each size class trapped). Modifications of traps also altered catch of cockroaches. Food bait tablets increased catch significantly; however, increases were small (<10%). Size of traps did not affect catch; whole traps or half traps caught the same number of cockroaches. Jar traps were much less effective than sticky traps, catching only half the number of cockroaches as sticky traps. A thin layer of petrolatum was a more effective barrier in jar traps to cockroach escape than powdered Olancha clay. Traps with petrolatum caught about twice as many cockroaches as traps with clay. Trapping of any of six life stages was not significantly affected by catch of any of the other stages. Rather, trap catch of each life stage was dependent on the number of that life stage available in the experimental arenas. In conclusion, of the traps tested, the Lo-line trap was the most sensitive for measuring cockroach catch, whereas the Detector trap (one third of trap) was the most economical trap (greatest sensitivity for lowest cost).     

Belly up: Reduced crevice accessibility as a cost of reproduction caused by increased girth in a rock‐using lizard

Costs of reproduction are any aspect of current reproduction that has the potential to reduce survivorship or reproductive output, and may include physiological costs or increased risks. Females of many species experience increased body mass, and increased girth, when gravid. Increased body mass reduces running speed and increases the cost of locomotion during pregnancy, but few studies have examined the cost of increased girth. If increased girth of gravid females reduces access to shelter from predators or the elements, increased girth could constitute a cost of reproduction. In the laboratory, we experimentally tested whether access to crevices was limited in viviparous, saxicolous female lizards (Eulamprus brachysoma), which use crevices for shelter, by measuring access to artificial crevices of known widths, and body height during and after pregnancy. Gravid E. brachysoma had significantly greater body height (11.2% on average), and as a result were forced to use significantly wider crevices (18.4% wider on average) than post‐parturition. Females with larger clutch sizes had wider mid‐bodies and required larger crevices. Control females, which were not gravid at either time of testing, showed no significant change in the size of crevice they could enter over time. If access to narrow crevices provides advantages such as protection from predators, or is important for thermoregulation, then gravid females may suffer a cost of reproduction because their access to narrower crevices is limited.     

Phenotypic variation in the breeding phenology of the woodlouse Armadillidium vulgare

Summary The breeding phenology of temperate wood-lice is strongly seasonal, the result of physiological constraints and precise environmental cues for reproduction. The adaptive value of such mechanisms is that the release of offspring coincides with favourable conditions for growth and survival (Willows 1984). We recorded the breeding phenology of Armadillidium vulgare (Latreille) on two grassland sites in Great Britain and found between-site and between-year variation in the onset of reproduction, the duration of reproductive activity, the release of offspring, the size of reproductive females and the number of broods per female. Between 82.7 and 97.7% of gravid females sampled were semelparous at 23 months, with the remainder iteroparous, producing a second brood after 35 months. On one site (Weeting Health) improved growth conditions during 1984 allowed some females (19.3% of gravid females sampled in that year) to produce a brood after 11 months. There was also an increase in the number of 3-year-old females found to be gravid. An experimental manipulation of the same habitat confirmed that such changes in life history tactics could be phenotypic responses. The observed phenotypic variation was sufficient to produce a range of life history tactics within a population. Mixtures of life history tactics within a population may be typical of invasive species and populations at the edge of the species range. Our results support the idea that phenotypic plasticity can be an appropriate tactic to maximise fitness in a fluctuating environment (Caswell 1983, 1989).     

Distribution, behavior, and course of patency of Dracunculus insignis in experimentally infected ferrets

From 106 ferrets experimentally infected with Dracunculus insignis, 273 female worms and 42 male worms were recovered. The percentage of female worms that mated, the location of all worms, and the rate of emergence of gravid females were recorded. Of 174 mature female worms recovered, only 11% had emerged before necropsy. Eighty-one percent of the male worms and 87% of all unmated (immature) females were found on the trunk of the animal or on the skin overlying it. Gravid female worms were found on the extremities (legs) 88% of the time. Almost one-third of gravid female worms were found on the left front leg. On 4 occasions, females were found in unusual locations: the tail, the cheek, the lumbar region of the spinal cord, and the peritoneal cavity associated with the omentum. The results showed that only a small percentage of mature female worms emerge, which suggests that infected persons harbor many more gravid female worms than indicated by reports of emergent worms. More than one-third of female worms were not mated, but it is likely that these immature females would be capable of further development. Furthermore, male worms have been observed to survive for up to 330 days, suggesting that male or unmated female worms may carry over from one transmission season to the next.     

Spatial memory in bank voles (Clethrionomys glareolus Schreb) assessed in the cue-controlled open field with the place of refuge

The capacity of bank voles (Clethrionomys glareolus Schreb) for rapid spatial learning was assessed in cue-controlled open field using their species-specific habits (high fear). Animals were tested in open field after 3 days of pretraining. During testing, novel stimuli (black-and-white geometric figures arranged in symmetric or asymmetric modes for different vole groups) were attached to a curtain surrounding the open field, and a shelter (a familiar box from the home cage) was introduced into the field. Testing consisted of four 10-min trials, the last (probe) trial was performed without the shelter. Time spent in different fielld areas was recorded. The voles remembered previous location of the shelter and preferred to visit this area. It was possible only in the condition with asymmetric arrangement of visual stimuli when animals could use them for navigation. The findings conclude that bank vole have a good capacity for rapid spatial learning.     

Identification of leucomyosuppressin in the German cockroach, Blattella germanica, as an inhibitor of food intake

The feeding pattern of the adult female of Blattella germanica peaks in the middle of the vitellogenic cycle. Following the hypothesis that a factor inhibiting gut peristalsis also inhibits food intake and is involved in the regulation of feeding, we searched for the most powerful myoinhibitory peptide in brain extracts from B. germanica females collected after the peak within the feeding cycle. Through HPLC purification and sequence analysis, we obtained the peptide leucomyosuppressin (LMS): pQDVDHVFLRFamide. LMS elicited a powerful myoinhibitory effect on B. germanica foregut and hindgut, with ED(50) values around 10(-10) M. In addition, it inhibited food intake in vivo in a dose-dependent manner at doses between 5 and 50 microg. The study of the distribution of ingested food in the foregut, midgut and hindgut of B. germanica females treated with LMS showed that food accumulates in the foregut, which may be due to the myoinhibitory effects of the peptide. We propose that this accumulation inhibits food intake because of the persistence of the signals from gut stretch receptors.     

Apple and peach fruit volatiles and the apple constituent butyl hexanoate attract female oriental fruit moth, Cydia molesta, in the laboratory

Volatiles emitted from immature and mature peach and apple fruits were all attractive to mated female oriental fruit moth, Cydia molesta (Busck), in a dual choice arena. Females did not discriminate between odours emitted by these two major host plants. The same natural blends were behaviourally ineffective for virgin females. A major component of apple fruit volatiles, butyl hexanoate, also attracted female C. molesta. Mated females were attracted to two medium dosages, while virgin females responded positively to the lowest of the five dosages tested. The time course of the captures of the moths shows a diurnal activity cycle known from the field. The possible implications of a semiochemical which attracts females are discussed in the context of previous findings that gravid females may immigrate from peaches into apple orchards particularly in the later phase of the season.     

THE BANDED MONGOOSE, MUNGOS MUNGO GMELIN

The banded mongoose is a social, diurnal, medium-sized carnivore classified in the family Viverridae. Packs of up to 32 animals were found to occupy a single, old termite mound for periods in excess of 2 months. Nine out of ten dens were in termite mounds, the other was in a gully. One den was excavated to show structure. The whole pack occupied the central chamber each night. One group of 32 consisted of 17 adults, 7 juveniles, and 8 babies too small to leave the den with the pack during the day. The animals were strictly diurnal, usually leaving the den about one hour after dawn; time of return was more variable, but was usually during the hour before dark. Senses of sight, smell and hearing were found to be very acute. During the day the packs covered large distances, foraging as they went. During the period of study, food (estimated by dung analysis) consisted almost entirely of Coleoptera (mainly dung beetles) and millipedes. The packs followed the trails of elephant and buffalo and obtained most of their food from their dung. Detailed behaviour is described. Mating was seen on three occasions and two males were seen to copulate with the same female. Family size was not determined, but eight young were seen to be suckled by three females indiscriminately. One mother looked after all eight young during the day when the pack was away. The animals used communal defaecating areas on and around the den, the faeces being scattered over the surface of the ground. Reactions to various animals, including predators, are described. When caught in the open the pack tended to bunch together acting as a single unit. If bushes were near they used them for shelter. Adaptations are discussed.