Vision in the common bed bug Cimex lectularius L. (Hemiptera: Cimicidae): eye morphology and spectral sensitivity.

Bed bugs as pests of public health importance recently experienced a resurgence in populations throughout the U.S. and other countries. Consequently, recent research efforts have focused on improving understanding of bed bug physiology and behaviour to improve management. While few studies have investigated the visual capabilities of bed bugs, the present study focused specifically on eye morphology and spectral sensitivity. A 3-D imaging technique was used to document bed bug eye morphology from the first instar through adult and revealed morphological characteristics that differentiate the common bed bug from the tropical bed bug as well as sex-specific differences. Electrophysiological measurements were used to evaluate the spectral sensitivity of adult bed bugs. Male bed bugs were more responsive than females at some wavelengths. Electrophysiological studies provided evidence for at least one photoreceptor with a spectral sensitivity curve peak in the green (λmax 520 nm) region of the spectrum. The broadened long wavelength portion of the spectral sensitivity curve may potentially indicate another photoreceptor in the yellow-green (λmax 550 nm) portion of the spectrum or screening pigments. Understanding more about bed bug visual biology is vital for designing traps, which are an important component of integrated bed bug management.

Climbing Ability of the Common Bed Bug (Hemiptera: Cimicidae).

Little is known about what factors influence the climbing ability of bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), in relation to the various surfaces they encounter. We examined how sex, time since last fed, and what surfaces the bed bugs were in contact with affected their climbing performance. The effects of sex and time since fed were tested by counting the number of bed bugs able to climb a 45° slope. The pulling force was recorded using an analytical balance technique that captured the sequential vertical pulling force output of bed bugs attached to various surfaces. Recently fed female bed bugs were found to have the most difficulty in climbing smooth surfaces in comparison with males. This difference can be explained by the larger weight gained from bloodmeals by female bed bugs. A variety of vertical pulling forces were observed on surfaces ranging from sandpaper to talc powder-covered glass. For surfaces not treated with talc powder, bed bugs generated the least amount of vertical pulling force from synthetically created 0.6-µm plastron surfaces. This vast range in the ability of bed bugs to grip onto various surfaces may have implications on limiting bed bugs dispersal and hitchhiking behaviors.

Potential population growth and harmful effects on humans from bed bug populations exposed to different feeding regimes.

Effects of host availability and feeding period on bed bugs, Cimex lectularius (L.) (Hemiptera: Cimicidae), were measured. Population growth and the potential harmful effect of bed bug populations on human hosts were modelled. Bloodmeal sizes were affected by both feeding length and frequency, with >2-fold difference between insects fed daily or weekly. Blood consumption increased >2-fold between bed bugs fed occasionally and often, and 1.5-fold between occasional and daily feeding. Bed bugs fed more often than once a week, potentially every 2-4 days. Egg production was associated with nutrition, being strongly correlated with blood consumption in the previous week. Bed bug populations can grow under different feeding regimes and are hard to control with <80% mortality. Bed bugs can survive and grow even in locations with a limited blood supply, where bed bug persistence may be important for the continual spread of populations. Persistence in non-traditional locations and a potential association with human pathogens increase the health risks of bed bugs. Potential blood loss as a result of a bed bug can have serious consequences because uncontrolled populations can reach harmful levels in 3-8 months. The reproduction potential of bed bug populations suggests serious consequences to human health and the need for efficacious control measures.

Behavioral and physiological response of Musca domestica to colored visual targets.

A better understanding of the visual attraction of house flies to colors and patterns is needed to improve fly trap performance. This study combined physiological responses measured with electroretinogram studies of the house fly's compound eyes and ocelli with behavioral attraction of flies to reflective colors and patterns in light tunnel assays. Compound eye and ocellar electroretinogram responses to reflected light were similar, with the largest responses to white and blue followed by yellow, red, green, and black. However, data from light tunnel behavioral assays showed that flies were attracted to white and blue light but were repelled by yellow. The addition of a black line pattern enhanced the attractiveness of blue visual targets, whereas yellow lines decreased attractiveness. Sensory input from the compound eye and the ocellus seems to be integrated to direct fly behavior. There is a direct correlation of house fly attractiveness to visual targets and the intensity of electrophysiological response, except for the yellow targets, which repel flies despite of intense electrophysiological response.

A case study of Megaselia scalaris (Diptera: Phoridae) causing ocular myiasis in a western hognose snake.

Late instar larvae of the scuttle fly, Megaselia scalaris Loew, were found near the right eye of a live captive-reared western hognose snake, Heterodon nasicus Baird and Girard. Dissection and removal of the snake's dorsal cranial bones revealed tissue degradation of the infected eye, the optic nerve, and the brain case; we suggest that these factors contributed to the death of this snake. This case study further demonstrates the opportunistic behavior of M. scalaris.

Control of Cimex lectularius using heat combined with dichlorvos resin strips.

Successful management of the bed bug, Cimex lectularius L. (Hemiptera: Cimicidae), is difficult because of its pesticide resistance, which can allow a reduction in population, but not elimination. We evaluated the effect of heat and/or air circulation on the efficacy of dichlorvos resin strips in the control of bed bugs. Treatments were performed in unoccupied dormitory rooms and consisted of dichlorvos resin strips containing 18.6% active ingredient, the same strips + fan, and strips + fan + heat. The mortality of recently fed bed bugs and weight loss of the dichlorvos strips were evaluated over 7 days. Dichlorvos resin strips killed bed bugs and eggs in just over 7 days. The addition of a fan or a fan + heat decreased time to 100% mortality to 3 days and 36 h, respectively. Eggs located in treated rooms did not hatch. Resin strips in the strips + fan treatment and the strips + fan + heat treatment volatilized 10 and 70 times, respectively, faster than strips in the strips-only treatment. The addition of heat in treatments with dichlorvos resin strips enhances the overall efficacy of the volatile insecticide and reduces the time required to eliminate live bed bugs and eggs.

Acoustic indicators for targeted detection of stored product and urban insect pests by inexpensive infrared, acoustic, and vibrational detection of movement.

Crawling and scraping activity of three stored-product pests, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), and Stegobium paniceum (L.) (Coleoptera: Anobiidae), and two urban pests, Blattella germanica (L.) (Blattodea: Blattellidae) and Cimex lectularius L. (Hemiptera: Cimicidae), were monitored individually by infrared sensors, microphones, and a piezoelectric sensor in a small arena to evaluate effects of insect locomotory behavior and size on the ability of an inexpensively constructed instrument to detect insects and distinguish among different species. Adults of all species could be detected when crawling or scraping. The smallest insects in the study, first-fourth-instar C. lectularius nymphs, could not be detected easily when crawling, but could be detected when scraping. Sound and vibration sensors detected brief, 3-10-ms impulses from all tested species, often grouped in distinctive trains (bursts), typical of impulses in previous acoustic detection experiments. To consider the potential for targeting or focusing detection on particular species of interest, indicators were developed to assess the likelihood of detection of C. lectularius. Statistically significant differences were found between C. lectularius and other species in distributions of three measured variables: infrared signal durations, sound impulse-burst durations, and sound pressure levels (energy) of impulses that best matched an averaged spectrum (profile) of scraping behavior. Thus, there is potential that signals collected by an inexpensive, polymodal-sensor instrument could be used in automated trapping systems to detect a targeted species, 0.1 mg or larger, in environments where servicing of traps is difficult or when timeliness of trapping information is important.

Toxicity of fatty acid salts to German and American cockroaches.

The toxicity of fatty acid salts to German, Blattella germanica (L.), and American cockroaches, Periplaneta americana (L.), was evaluated. Potassium and sodium laurate caused up to 95% mortality of German cockroaches and 100% mortality of American cockroaches. Even-numbered potassium fatty acid salts, C8-C18 were assessed for toxicity at 0.125, 0.25, 0.5, 1, and 2% concentrations by a 30-s immersion of cockroaches. The more soluble of the fatty acid salts at 2% concentration caused 65-95% mortality of German cockroaches and 100% mortality of American cockroaches. Potassium oleate, C18, was most toxic to both German (LC50 = 0.36%) and American (LC50 = 0.17%) cockroaches. Fatty acid salt solutions on a substrate were tested by placing cockroaches in contact with treated floor tiles immediately after application (wet) or after the solutions had dried. Sodium laurate and potassium caprate caused mortality of German (62 +/- 17.4 and 58 +/- 12.6%, respectively) and American cockroaches (52 +/- 18.5 and 28 +/- 4.9%, respectively) on wet tiles, whereas potassium oleate caused mortality of German cockroaches (67 +/- 14.1%) only. Dry fatty acids caused no mortality among exposed cockroaches. Fatty acid salt solutions can be effective in killing German and American cockroaches but only when insects are thoroughly wetted with 1-2% fatty acid salt solutions.

A microcomputer-based activity meter for multiple animals.

We describe and validate a computer-video system that records and displays in real-time the activity of multiple specimens in a user-defined space, at user-defined intervals. The computer program uses image subtraction algorithms to record changes in video images, and stores observations in column format or as a series of 2-D matrices. The program was tested under various lighting conditions, backgrounds, specimen size and specimen speed. An AV model of Macintosh computer with video input from a camera or video cassette recorder was used to record and analyze the mechanical movement of spots on a turntable and the locomotor activity of an ant colony. The limitations and potential applications of the program are discussed.

A microcomputer-based system for real-time analysis of animal movement.

A microcomputer-based video system for tracking, recording, and analyzing the movement of animals in two dimensions on variegated background in real-time has been developed and validated, both mechanically and with moving animals. Hardware and software (donationware) costs are low. Specimens visualized as small as 3 pixels long may be tracked in an arena that is 240 x 320 pixels in size. The results of tracking a mechanical moving spot are compared with a theoretical circular path. Comparisons between frame-by-frame human observation and computer generated X-Y coordinates are also presented. Applications of the tracking system include insect toxicology and pheromone bioassay, vertebrate locomotion studies, and basic research on taxes and kineses.

Age- and sex-related effects in German cockroaches fed an allopurinol diet (Dictyoptera: Blattellidae).

The effects of feeding several ages of adult and nymphal German cockroaches a laboratory rat chow diet containing 0.10% allopurinol were investigated. All cockroaches fed the allopurinol diet suffered increased mortality. The range of LT50 values (the time required to kill 50% of an experimental cohort) for four ages of nymphs (1-8, 16-23, 21-28, and 28-35 d old following hatch) continuously fed the allopurinol diet was 1.36 wk (4.72-6.08 wk). Regardless of sex, young adult (1-7 d old following eclosion) cockroaches fed the allopurinol diet died significantly sooner than older adults (28-35 d old following eclosion); males died significantly sooner than females. All females fed the allopurinol diet as nymphs aborted their oothecae. Although an initial ootheca were hatched from cockroaches fed the allopurinol diet as adults, all subsequent oothecae were aborted. Untreated females mated with allopurinol-fed males experienced successful reproduction, but allopurinol-fed females mated with either allopurinol- or control diet-fed males failed to reproduce. Evidence suggests that cockroaches suffer increased mortality and reproductive failure from increased levels of hypoxanthine and xanthine.

Larvicidal effects of boric acid and disodium octaborate tetrahydrate to cat fleas (Siphonaptera: Pulicidae).

Borate products varied in efficacy against larval cat fleas, Ctenocephalides felis felis Bouché, with some effective at rates of 23 micrograms/cm2 when larvae were exposed to the compounds in sand. Powdered boric acid, granular boric acid, and disodium octaborate tetrahydrate (Polybor) at rates of 200 micrograms/cm2 produced < or = 90% mortality of larvae exposed in carpet for 96 h. LC50 values of larvae exposed in treated carpets for 96 h were 23 micrograms/cm2 for powdered boric acid, 40 micrograms/cm2 for granular boric acid, and 47 micrograms/cm2 for polybor.

Rearing improvements for the German cockroach (Dictyoptera: Blattellidae).

Known-age cohorts of three strains of German cockroach, Blattella germanica (L.), were mass-reared by establishing one rearing container each week (so that cockroaches within a container would be of known age). An average of 330-443 females was placed in oviposition units within these rearing containers. Percentage hatch of oothecae was 77.49-84.63%, resulting in an average of 12,258-16,359 nymphs per rearing container. Development of nymphs was similar for the three strains. Survivorship of nymphs to the adult stage was 19.95-29.56%; survivorship was significantly higher for the strain most recently colonized from the field. Adult emergence occurred at 6-7 wk, and average production per container was 2,834-3,971 cockroaches.

Host grooming efficiency for regulation of cat flea (Siphonaptera: Pulicidae) populations.

Grooming efficiency was studied by infesting domestic short-hair cats, Felis catus L., with known numbers of cat fleas, Ctenocephalides felis felis Bouché, then collecting the cat feces and extracting the fleas to determine how many had been groomed off, varying the infestation level. Some hosts were found to be significantly more efficient at grooming fleas than others, with the best groomer removing 17.6% of its flea burden daily, compared with only 4.1% removed by the poorest groomer. Cats were more efficient at grooming fleas at infestations of < 50 fleas and > 150 fleas. Mean on-host flea longevity was 7.8 d.

Spray-dried bovine blood: an effective laboratory diet for Ctenocephalides felis felis (Siphonaptera: Pulicidae).

Commercially available spray-dried protein sources were evaluated as replacement laboratory cat flea, Ctenocephalides felis felis (Bouché), larval diets for slaughterhouse-collected heat-dried blood. Percentage of adult emergence of fleas reared on adult flea feces (87.7%) and spray-dried bovine blood (79%) did not significantly differ, and yeast supplementation did not significantly increase adult emergence for spray-dried diets. However, yeast supplementation of heat-dried blood increased percentage adult emergence from 0 to 41.7%. Spray-dried bovine blood was found to be a satisfactory laboratory diet for cat flea larvae.

Laboratory method for measuring the attractiveness of pheromones to adult Musca domestica (Diptera: Muscidae).

A technique was developed for evaluating the effects of pheromones on adult house fly, Musca domestica (L.) feeding. U-shaped pipettes were placed next to Celotex blocks treated with (Z)-9-tricosene in cages with 200 adult house flies. The pipettes were filled with sucrose so that a positive meniscus formed where flies could feed. The amount of sucrose consumed was determined by measuring the amount needed to refill the pipettes after 24 h. Flies ingested significantly more sucrose solution placed near a Celotex block treated with (Z)-9-tricosene than from a control without pheromone. The cis and cis/trans isomers of (Z)-9-tricosene were equally effective in increasing ingestion. Commercially available polyvinylchloride strips were not as effective as the Celotex block when both were treated with (Z)-9-tricosene. Evaluation of these (Z)-9-tricosene presentations using our new laboratory method precluded the need for more costly field evaluations.

Diel patterns of cat flea (Siphonaptera: Pulicidae) egg and fecal deposition.

The quantity of eggs and feces deposited by replicate populations of cat fleas, Ctenocephalides felis (Bouché), from domestic house cats. Felis catus, were recorded at 1-h intervals over a 24-h period, in a photoperiod of 12:12 (L:D) (photophase, 0600-1800 hours [EST]). Egg production averaged 23.96 +/- 0.83 eggs per female per day and was greatest from 2400 to 0300 hours and lowest from 0700 to 0900 hours and from 1700 to 1900 hours. Daily fecal deposition was 0.77 +/- 0.03 mg feces per flea and did not vary significantly among hours. Flea eggs and adult feces were dropped continuously from infested cats, but significantly more eggs were shed at times of day when cats normally rest. More feces are concentrated in the small areas where cats rest than over the large areas they roam. Consequently, eggs and feces would not be deposited uniformly throughout the hosts home range, resulting in a clumped distribution of larval development sites at host resting areas.

Volatile effects of insect growth regulators against the German cockroach (Dictyoptera: Blattellidae).

Third-instar German cockroach nymphs were held to maturity in continuous proximity to test surfaces treated with hydroprene and fenoxycarb, which they were unable to contact directly. Surfaces tested were unfinished plywood, fiberboard, vinyl tile (absorbent surfaces), glass, stainless steel, ceramic tile, and formica (nonabsorbent surfaces). Number of oothecae, percent egg hatch, and survival did not differ between any fenoxycarb treatment and the untreated controls, but there was significant wing twisting (76-94%) for all nonabsorbent surfaces. Number of oothecae was significantly lower and percent wing twisting was significantly higher for all hydroprene-treated surfaces with respect to the untreated controls, although survival was not affected. These effects were less pronounced for the nonabsorbent surfaces. These results indicate that hydroprene, but not fenoxycarb, has significant biological activity through volatile action when applied at current label rates. This activity is likely to have important consequences for control, especially for "crack and crevice" applications in confined spaces.

Outdoor survival and development of immature cat fleas (Siphonaptera: Pulicidae) in Florida.

In north-central Florida, cat flea, Ctenocephalides felis felis Bouché, larvae survived outdoors year round. Their survival was greatest (up to 84.6%) outdoors in the fall, from September to November, when both temperatures and relative humidities were moderate. Female cat fleas developed faster than males. Development times for flea larvae were shortest (20-24 d) in June and July. From January to March, flea larval mortality was highest (91.7-100%) and development times the longest (36-50 d) outdoors. This was the result of low temperatures and low relative humidities associated with the passage of cold fronts during this time of year. Flea larvae survived light frosts in protected microhabitats such as inside a doghouse and under a mobile home.

Spectrophotometric method of quantifying adult cat flea (Siphonaptera: Pulicidae) feces.

Cat flea, Ctenocephalides felis felis (Bouché), feces are an essential part of larval nutrition under natural conditions. The mass values of adult flea feces can be measured by dissolving samples of flea feces in Drabkin's reagent, filtering, centrifuging, and measuring absorbance spectrophotometrically at 540 nm. Either flea feces or air-dried host blood can be used to generate the standard curve used to convert absorbance (optical density) values into mass values. Debris collected from flea-infested house cats averaged 23.02 mg debris per cat per h with an average of 10.41 mg flea feces per cat per h. Flea feces deposited in the environment serve as potential larval food. Adult flea feces comprised an average of 44.28% of the debris deposited from infested domestic house cats in this study.