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The Madagascar hissing cockroach (Gromphadorhina portentosa) has become popular as a pet and as an educational tool in classrooms, zoos, and museums.

We performed experiments to determine whether an extract of Sarcoptes scabiei(De Geer) influenced cytokine expression by human T-lymphocytes. Peripheral blood mononuclear cells from five sensitized donors and four donors without sensitization to scabies mites were challenged with a T-cell mitogen alone, with scabies extract (SS) alone, or with mitogen and SS together. Supernatants were analyzed for the cytokines interferon-γ (IFNγ), interleukin (IL)-2, IL-4, and IL-10. No IL-2 or IL-4 was produced in response to scabies extract. Cells from both naïve and sensitized donors produced large amounts of IFNγ and IL-10. The lack of IL-4 but high levels of IL-10 suggests that IL-10 was likely secreted by type 1 T-regulatory cells, which were activated by something in the scabies extract. IL-10 has anti-inflammatory and immune-suppressive effects. It may play a key role in depressing the inflammatory and immune responses in humans so that clinical symptoms are not seen until 4–6 wk after a person becomes infested with scabies mites.

Storage mites of the families Chortoglyphidae, Glycyphagidae, Echimyopodidae, and Acaridae are commonly found in agricultural and nonagricultural environments. The prevalence of sensitization to these storage mites in the general population in the United States is unknown.

Background: Few studies have investigated live house dust mite and mite allergen removal from clothing and bedding by washing machines. No studies have investigated the transfer of mites from infested to uninfested clothing and bedding during washing. Objective: The purpose of this study was to wash different types of clothing and bedding in residential washing machines to determine the live Dermatophagoides farinaemite and allergen removal and the mite transfer from mite-infested items to mite-free items. Methods: Clothing and bedding items were machine washed in 6- and 8-lb loads in warm (36°C-38°C) or cold (22°C-27°C) water with and without recommended concentrations of laundry detergent and sodium hypochlorite bleach. Live mites and allergen present in washed versus unwashed and washed mite-infested versus washed mite-free items were compared. Results: Washing clothing and bedding in water alone, detergent, or detergent plus bleach removed 60% to 83% of the live mites. Washing removed more mites from some items than from others. When mite-infested items were washed with identical sets of mite-free items, many live mites were transferred to the previously mite-free items. Overall, 84% of Der f 1 was removed from items washed in water alone or in detergent and 98% from items washed in detergent plus bleach. Conclusions: Washing clothing and bedding in cold or warm water with detergent or detergent plus bleach removed most allergen and a significant (P< .05) portion of live mites. Repeated washing is required to further reduce mite levels. Live mites were transferred from mite-infested to mite-free items during washing. (J Allergy Clin Immunol 2003;111:1269-73.)

House-dust mites in clothing and bedding are the source of major allergens. Based on studies ofDermatophagoides pteronyssinusonly, weekly washing in hot water is recommended to kill dust mites and remove allergens from clothing and bedding. However, in the United States, washing is most often done in warm or cold water, and other mite species are involved.

Locations where there are no dust mites or pets present may contain allergens that pose a risk factor for sensitizing and inducing rhinitis and asthma.

Removing allergen from the indoor environment should be a primary strategy for the management and treatment of allergic disease.

In most temperate humid areas of the world, house dust mites are a major source of multiple allergens in house dust. Mite allergens sensitize and induce perennial rhinitis, asthma, or atopic dermatitis in a large portion of patients with allergic disease. There is convincing evidence that avoidance of mite allergen can effectively reduce allergic symptoms. Patients can be moved to a mite allergen–free environment, or mite and mite allergen abatement can be performed to reduce exposure in existing residences. Some knowledge of the biology of house dust mites is essential to understand the basis of the recommendations for reducing mites and mite allergens in homes and to appreciate the difficulty of eliminating house dust mites and mite allergens from homes. This article reviews key aspects of the biology of dust mites, the properties of mite allergens, recommendations for reducing mite and mite allergen concentrations in homes, and practical recommendations for treatment. (J Allergy Clin Immunol 2001;107:S406-13.)

Background:Maintaining a relative humidity (RH) of less than 50% is one recommendation for reducing numbers of house dust mites and their allergens in homes. Objective:The purpose of this study was to determine whether, in a humid temperate climate, indoor RH could be sufficiently lowered to control dust mites and their allergens. Methods:During a period spanning 2 humid summers (May 1998 to October 1999), dust mite and allergen densities were determined in 3 groups of homes. One group (low RH group, n = 23) maintained an RH of less than 51%. Most of these homes used a high-efficiency dehumidifier and air conditioning. A second group of homes (group A) used air conditioning only (n = 19) or air conditioning and dehumidification (n = 5) but did not maintain an RH of less than 51%. A third group of homes (group C, n = 24) controlled climate by opening windows and had an RH of greater than 51%. Normal housecleaning was maintained in all homes during the study. Results:The low RH group homes started in June with a mean ± SE of 401 ± 124 live mites and 17 ± 3 μg of total Der 1 allergen per gram of dust. After 17 months of maintaining an RH of less than 51%, these declined significantly to 8 ± 3 live mites per gram (P= .004) and 4 ± 1 μg of Der 1 per gram of dust (P< .001). In contrast, group A and C homes exhibited seasonal peaks of 500 to 1000 mites and 40 to 70 μg of Der 1 per gram of dust. At all time points after the baseline sample, the low RH group homes had significantly less (P< .001) allergen than the group A and C homes. After 17 months, allergen levels were more than 10 times lower in low RH homes compared with humid homes. Conclusion:This study showed that it is practical to maintain an indoor RH of less than 51% during the humid summer season in a temperate climate, and this resulted in significant reductions in mite and allergen levels. (J Allergy Clin Immunol 2001;107:99-104.)

A researcher experienced allergic symptoms while working with the astigmatid mite Hemisarcoptes cooremanicultured on scale insects. This mite is a predator of scale insects that often parasitize many perennial vascular plants in orchards, gardens, and ornamental nurseries worldwide; therefore, orchard and ornamental nursery workers and gardeners may be exposed to this mite.

We investigated exposure to house dust mites and freshly cleaned carpets in patients with Kawasaki syndrome (KS) who resided in Denver, CO. House dust samples were analyzed for mites (Dermatophagoides pteronyssinusand Dermatophagoides farinae) and convalescent sera were assayed for immunoglobulin G antibody to mite antigen. House dust samples from case and neighborhood control homes showed no difference in the prevalence of mites. Fewer than 10 of dust samples from either group revealed evidence of live or dead mites. Nine of 18 (50) children with KS had a prior history of exposure to freshly cleaned rugs within the 45 days of the onset of KS compared with 3 of 11 (27) neighborhood controls. There was no difference in mean anti-mite antibody concentrations between convalescent sera from KS cases and sera from pediatric hospitalized controls. We conclude that in Denver KS can occur in the absence of significant mite exposure as defined by environmental studies or serologic means.

Net water gain and loss by partially dehydrated female house dust mites, Dermatophagoides farinae,were measured in several combinations of water vapor activity (av) and temperature. At some specific av's and temperatures experimental mites continued to dehydrate while at others mites rehydrated by extracting water from ambient water vapor. The lowest avat which a net gain of water occurred (critical equilibrium activity, CEA) was directly proportional to temperature; CEA's were 0.69 at 35 C, 0.63 at 30 C, 0.58 at 25 C, and 0.52 at 15 C.

Allergic sensitivity to storage mites is common in farmers and others who work in environments where hay and grain are handled, stored, or processed. The clinical importance of storage mite-induced allergy in these individuals is generally unknown in the United States. Tyrophagus putrescentiaeis a common storage mite, the allergenicity of which has not been characterized.

The domestic mites Euroglyphus mayneiand Blomia tropicalisfrequently co-inhabit homes in subtropical/tropical regions around the world. Both species are the source of substances that cause allergic reactions in patients.

The pruritic skin disease scabies is caused by the burrowing of the itch mite Sarcoptes scabiei (De Geer). It is difficult to diagnose this disease because its symptoms often resemble those of other skin diseases. No reliable blood or molecular diagnostic test is available. The aim of this project was to begin to characterize the scabies proteome to identify scabies mite proteins, including those that may be useful in the development of a diagnostic test or vaccine. Various scabies mite extracts were separated by two-dimensional electrophoresis, and 844 Coomassie Blue-stained protein spots were excised, subjected to trypsin digestion, and analyzed by Matrix Assisted Laser Desorption/Ionization Time-Of-Flight/Time-Of-Flight (MALDI-TOF/TOF) mass spectrometry (MS). Tryptic fragment sequences determined by MS were searched against the recently completed S. scabiei annotated genome, leading to the identification of >150 proteins. Only 10 proteins hit to previously identified scabies proteins including actin, tropomyosin, and several ABC transporters. Thirteen proteins had homology to dust mite allergens (members of groups 8, 10, 13, 17, 20, 25, and 28). Most other sequences showed some homology to proteins in other mites and ticks including homologs of calmodulin, calreticulin, lipocalin, and glutathione-S-transferase. These data will now allow the identification of the proteins to which scabies patients produce antibodies, including those that may be good candidates for inclusion in a diagnostic test and vaccine.

Stored product mites commonly occur in agricultural work environments and sometimes in homes in significant numbers. They are a source of allergens that sensitize and induce allergic reactions. This may include atopic dermatitis. The purpose of this investigation was to determine if the common species of storage mites are the sources of molecules that influence the function of human dermal microvascular endothelial cells that regulate the trafficking of inflammatory and immune cells into the dermis during allergic reactions and other skin diseases. Human dermal microvascular endothelial cells were challenged with varying doses of extracts of the storage mites Acarus siro L., Chortoglyphus arcuatus (Troupeau), Lepidoglyphus destructor (Schrank), or Tyrophagus putrescentiae (Schrank) and the secretion of cytokines and expression of adhesion molecules were measured. The role of endotoxin and protein in inducing these responses was evaluated. These stored product mite extracts induced secretion of interleukin-6, interleukin-8, monocyte chemotactic protein-1, and granulocyte/monocyte colony stimulating factor. Some of these effects were induced by protein present in the extracts, some were induced by endotoxin, and some were induced by other substances. C. arcuatus and T. putrescentiae extracts also down-regulated tumor necrosis factor a-induced vascular cell adhesion molecule-1 expression. Stored product mite extracts contain an assortment of molecules, including endotoxins and proteins, which modulate the expression of cell adhesion molecules and the secretion of cytokines by microvascular endothelial cells. These modulating properties varied among mite species indicating that each mite species has a unique set of molecules that is responsible for its activity.

Previous in vitro studies showed that molecules in an extract of the mite Sarcoptes scabiei variety canis De Geer could modulate the secretion of cytokines from cultured normal human epidermal keratinocytes and dermal fibroblasts in the absence of proinflammatory cytokines in the cell culture media. The purpose of this study was to investigate whether scabies extract could also modulate cytokine and chemokine secretion from epidermal keratinocytes and dermal fibroblasts in the presence of proinflammatory cytokines that are likely present in the scabietic lesion in vivo. In particular, could the downmodulating properties of this ectoparasitic mite on skin cells be maintained in the presence of proinflammatory cytokines? We found that even in the presence of the proinflammatory cytokines interleukin (IL)-1a, IL-1ß, and a mixture of tumor necrosis factor (TNF)a + IL-17, scabies extract still downregulated the levels of IL-8 secretion from keratinocytes and fibroblasts and of granulocyte/macrophage-colony stimulating factor (GM-CSF) secretion from fibroblasts that were induced by stimulation of the cells with proinflammatory cytokines alone. This study also showed that scabies molecules induced secretions of growth-related oncogene a (GROa), transforming growth factor a (TGFa), and cutaneous T-cell attracting chemokine (CTACK) from keratinocytes and IL-6 and granulocyte-colony stimulating factor (G-CSF) from fibroblasts. These findings, coupled with the previous findings that molecules in scabies extract could downregulate expression of intracellular adhesion molecule-1 (ICAM-1) and E-selectin by normal dermal microvascular endothelial cells and secretion of IL-1ra from keratinocytes, suggest that multiple factors from scabies mites play a role in the characteristic delayed inflammatory response to a primary infestation with S. scabiei. These are adaptations that favor invasion of the host by the parasite.

The human skin contacts molecules from house dust mites that are ubiquitous in many environments. These mite-derived molecules may penetrate the skin epidermis and dermis and contact microvascular endothelial cells and influence their function. The purpose of this study was to determine the response of normal human dermal microvascular endothelial cells to extracts of the dust mites, Dermatophagoides farinae, D. pteronyssinus, and Euroglyphus maynei with and without endotoxin (lipopolysaccharide). Endothelial cells were stimulated with mite extracts and the expression of surface molecules and the secretion of cytokines were measured in the absence and presence of polymyxin B to bind endotoxin. All three mite extracts stimulated endothelial cells to express intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin and to secrete interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP-1), and granulocyte/macrophage colony stimulating factor (GM-CSF). Euroglyphus maynei-induced expression of all the cell surface molecules was not inhibited when the endotoxin activity in the mite extract was inhibited. In contrast, endothelial cells challenged with D. farinae or D. pteronyssinus extract depleted of endotoxin activity expressed only constitutive levels of ICAM-1, VCAM-1, and E-selectin. D. farinae and E. maynei extracts depleted of endotoxin activity still induced secretion of IL-8 and MCP-1 but at reduced levels. Only constitutive amounts of IL-6, G-CSF, and GM-CSF were secreted in response to any of the endotoxin-depleted mite extracts. Extracts of D. farinae, D. pteronyssinus, and E. maynei contain both endotoxins and other molecules that can stimulate expression of cell adhesion molecules and chemokine receptors and the secretion of cytokines by normal human microvascular endothelial cells.

The clinical signs of a Sarcoptes scabiei (De Geer) (Acari: Sarcoptidae) infestation are initially delayed, which suggests that the mites can depress the immune/inflammatory response. The purpose of this study was to investigate the modulatory properties of scabies mites in vivo at the gene expression level in a secondary lymphoid organ that is involved in initiating an immune response to the parasite. We found that substances from scabies mites influenced the expression of mRNA for molecules that participate in the sequestering of lymphocytes in the periarteriolar lymphoid sheath, primary follicle, and marginal zone of the spleen. Mice exposed to live scabies mites exhibited decreased mRNA expression for the adhesion molecules intercellular adhesion molecule (ICAM)-1, ICAM-2 and L-selectin; the cytokines tumor necrosis factor (TNF)a and CCL5; and the receptors for several other cytokines including TNF and interferon ?. In addition, exposure to live mites or vaccination with a scabies extract resulted in reduced expression of mRNA for B7–2, CD40, CD4, CD8, and CD45, thereby potentially reducing the physical interactions between B cells and T-helper (Th)2 helper cells, between Th1 and Tc cells, and between T-helper cells and antigen-presenting cells, thus depressing their function in response to thymus-dependent antigen. Live scabies mites also depressed expression of toll-like receptors 2, 4, and 6. In conclusion, our results indicate that live mites produce substances that can down-regulate expression of adhesion molecules, cytokines, chemokines, chemokine receptors, and lymphocyte surface molecules involved in leukocyte sequestering and the interaction of B and T cells during activation of an immune response in the spleen.

Many of the previously characterized allergens of house dust mites are known to be proteases, and this enzymatic activity is thought to contribute to their allergenicity. Other astigmatid mites, including stored-product mites and the ectoparasitic itch mite, Sarcoptes scabiei De Geer, are also known to be allergenic, but little or nothing is known about their enzymatic activities. The purpose of this study was to characterize the enzymatic activities present in extracts of the parasitic itch mite and from eight other species of free-living astigmatid mites. Extracts were prepared from one parasitic mite (S. scabiei), five stored-product mites (Chortoglyphus arcuatus (Troupeau), Lepidoglyphus destructor (Schrank), Blomia tropicalis Bronswijk, Cock, Oshima, Tyrophagus putrescentiae (Schrank), and Acarus siro L.), and three house dust mites [Dermatophagoides farinae Hughes, Dermatophagoides pteronyssinus (Troussart), and Euroglyphus maynei (Cooreman)]. ApiZym strips were used to screen for the presence of 19 individual enzyme activities. Digestion of nine other substrates was evaluated by spectrophotometric or electrophoretic methods. All mite extracts exhibited some form of phosphatase, esterase, aminopeptidase, and glycosidase activity, although their substrate specificities varied considerably. Itch mite extract did not possess detectable serine peptidase activity nor was it able to hydrolyze gelatin or casein, whereas all other mite extracts exhibited these activities. Storage mite extracts possessed enzymes capable of degrading the widest range of substrates, whereas itch mite extract had the most limited proteolytic capacity. Extracts of nine species of allergy-causing astigmatid mites contain wide and diverse repertoires of enzymatic activities. These catalytic activities may be important contributors to the induction and manifestation of inflammatory and immune responses to mites in patients.

The inflammatory and immune responses seen with the worldwide disease scabies, caused by the mite Sarcoptes scabiei (De Geer) (Acari: Sarcoptidae), are complex. Clinical symptoms are delayed for weeks in patients when they are infested with scabies for the first time. This study was undertaken to elucidate the role of the human dermal microvascular endothelial cell (HMVEC-D) in modulating the inflammatory and immune responses in the skin to S. scabiei. Extracts of S. scabiei were incubated with HMVEC-D and the expression of adhesion molecules and chemokine receptors on the cells and the secretion of selected cytokines were determined by enzyme-linked immunosorbent assay. S. scabiei extract was found to inhibit HMVEC-D expression of E-selectin and vascular cell adhesion molecule-1, although not intercellular adhesion molecule-1. The secretion of interleukin-8 also was inhibited by S. scabiei extract. S. scabiei extract increased expression of the chemokine receptor CXCR-1 and both down-regulated and up-regulated expression of CXCR-2, depending on the concentration tested. These findings help explain the delayed inflammatory reaction to infestation with S. scabiei.

Sarcoptes scabiei (De Geer) mites burrow in the nonliving stratum corneum of the epidermis of their mammalian hosts. These mites ingest extracellular fluid (serum) that seeps into the burrow from the lower vascular dermis. A strong host antibody response occurs when mites die in the skin. This suggests internal immunogenic proteins are released into the host at this time. Vaccination with internal antigens may be an approach to protect against this mite if host antibody to internal antigens that regulate key physiological processes is ingested along with serum. Our study clearly showed that scabies mites ingest host immunoglobulin as evidenced by the localization of fluorescent-labeled antibody to host immunoglobulin in the anterior midgut and esophagus of fresh mites removed from the host. This is the first study that demonstrates that this nonblood-feeding ectoparasitic mite ingests host antibody while feeding on tissue fluid that seeps into the stratum corneum.

Serum from seven patients with ordinary scabies and six with crusted scabies were screened by immunoblotting for IgE- and IgG-specific proteins in an extract of the mite, Sarcoptes scabiei variety canis. Sera from atopic individuals without sensitivity to house dust mites were used as controls. Serum from all of the patients with crusted scabies showed strong IgE binding to 11–21 and IgG binding to 1–7 scabies proteins. In contrast, three of the seven patients with ordinary scabies showed IgE binding to one to six scabies proteins, and their antibody binding was much weaker. Patients with crusted scabies had serum antibody that reacted with larger molecular weight proteins compared with patients with ordinary scabies. The results of this study indicate that patients with crusted scabies showed a pronounced IgE response to scabies mites, whereas patients with ordinary scabies did not.

We performed a series of experiments to determine if human peripheral blood mononuclear cells (PBMCs) from a healthy donor and dendritic cells (NHDCs) derived from these PBMCs reacted to molecules in a scabies extract. PBMCs extravasate from the circulatory system and enter tissues such as scabietic lesions, where monocytes become macrophages. Cells were cultured in medium alone or medium containing 50 µg/ml of Sarcoptes scabiei (SS) extract, 50 ng/ml E. coli lipopolysaccharide (LPS), or SS + LPS together. Supernatants were collected and assayed by enzyme-linked immunosorbent assay (ELISA) for specific cytokines. PBMCs stimulated with SS or LPS exhibited moderately upregulated production of interleukin (IL)-1ß and huge increases in secretions of IL-6, IL-8 and TNF-a. Cells co-stimulated with both SS and LPS generally secreted more of these cytokines than cells stimulated with either SS or LPS alone. LPS induced a small amount of IL-1a secretion, whereas SS did not, and neither additive resulted in the production of IL-10. NHDCs did not produce IL-1a, IL-1ß, IL-6, IL-8, or IL-10 in response to stimulation with SS. These cells did produce IL-6, IL-8, and tumor necrosis factor (TNF)-a in response to LPS. When cells were co-stimulated with both LPS and SS, the production of IL-6 and IL-8 was significantly reduced compared with the levels secreted after LPS stimulation alone. These studies show that molecules in a whole body extract of S. scabiei modulate the function of PBMCs (probably monocytes) and dendritic cells.

In a controlled laboratory study, disodium octaborate tetrahydrate (DOT) applied to carpets with a carpet-cleaning machine at a rate of 509 ml DOT/8.15 liter H2O/100 m2 (two cups DOT/2 gal H2O/100 feet2) reduced survival and population growth of live Dermatophagoides farinae and Dermatophagoides pteronyssinus by =98% compared with water-cleaned and uncleaned carpets at 8 wk postcleaning. Cleaning with DOT was more effective against D. pteronyssinus than D. farinae.

We determined the survival, development, and fecundity of Dermatophagoides farinae Hughes exposed to fluctuating daily regimes of hydrating and dehydrating relative humidity. Larva emerged from 84, 92, and 94% of eggs incubated at a regime of 2, 4, and 8 h at 75% RH and 22, 20, and 16 h at 0% RH, respectively. No emerging offspring completed the life cycle when exposed to the 2 and 4 h of moist air daily but 44 and 53% survived for 70 d in the larval or nymphal stages, respectively, and these completed development to adults when subsequently held at a constant 75% RH. Given 8 h of moist air daily, 41% of emerging offspring completed the life cycle but development was 1.6 times longer compared with development at a constant 75% RH. For all daily hydrating and dehydrating regimes, a greater percentage of offspring became males than females. Overall, survival of immatures was remarkable at these daily long periods of dehydrating conditions when a short period of hydrating moisture was provided. When exposed to a daily regime of 4 h of moist air (75% RH) and 20 h of dry air (0% RH), 84% of females survived 28 d and produced ˜⅓ of the number of eggs produced at constant 75% RH (control).

Reducing relative humidity to <50% in homes is recommended as one means of reducing dust mite populations in the homes of those who suffer allergies to house dust mites. Because of some activities in the home (e.g., bathing, cooking, opening windows), it may not be possible to keep relative humidity constantly <50%. We determined how the fluctuating daily regimes of hydrating (75%) and dehydrating (35%) relative humidities affected the development of Dermatophagoides farinae Hughes. The life cycle was completed (egg to adults) when mites were given regimes of 24 h at 75% RH, 8 h at 75% and 16 h at 35% RH, 6 h at 75% and 18 h at 35% RH, and 4 h at 75% and 20 h at 35% RH. The time required to complete development was inversely related to the amount of moist air given daily. Development took 58.3 ± 1.44, 64.7 ± 1.87, and 82.4 ± 2.39 d for 8, 6, and 4 h of moist air daily, respectively. In comparison, the life cycle was completed in 41.1 ± 0.50 d when development occurred at a constant 75% RH. Egg incubation time was significantly longer for fluctuating ambient relative humidity compared to a continuous 75 or 35% RH. Of the emerging larvae 53.8, 72.7, 62.7, and 85.0% completed the life cycle when given 4, 6, 8, and 24 h 75% RH daily and 35% RH for the remainder of the day. This study revealed that D. farinae can complete development when given only short periods of moist air daily but the rate of development is much slower than development at a constant 75% RH. Therefore, reducing ambient relative humidity does reduce the rate of development of mite populations and the accumulation of dust mite allergen.

Experiments were conducted to determine the effects of relative humidity on the population dynamics of single and mixed species of Dermatophagoides farinae Hughes, D. pteronyssinus (Trouessart), and Euroglyphus maynei (Cooreman) at specific relative humidities maintained at 20°C, with unlimited food. The population density of single and mixed species (D. farinae and D. pteronyssinus) increased exponentially when cultured at 65, 70, and 75% RH. The mean population growth rates were 17.3 ± 4.4 SD and 32.5% ± 4.7/wk for D. farinae and D. pteronyssinus, respectively. Mean population doubling times were 2.2 ± 0.3 and 4.2 ± 1.3 wk for D. pteronyssinus and D. farinae, respectively. Mixed species cultures, started with equal numbers of D. farinae and D. pteronyssinus, resulted in higher percentages of D. farinae than D. pteronyssinus. In cultures started with 75% of one species and 25% of the other, the more numerous species remained dominant and in similar ratios throughout the experiment. Both D. farinae and D. pteronyssinus population densities maintained at 85% RH declined over a 12-wk culture period because of mold growth. E. maynei were unable to survive at 65, 70, 75, and 85% RH, which indicated that their climatic requirements were different from those of D. farinae and D. pteronyssinus. Population densities of D. farinae and D. pteronyssinus cultures declined when held at 21–22°C and relative humidities of =50%; however, at 50% RH, significant proportions of the populations survived for 10 wk. Half-life for desiccation of D. farinae and D. pteronyssinus at 45% RH was 11.5 and 1.2 wk, respectively, but at 50% RH was 86.3 and 4.0 wk, respectively. The data indicated that a =5O% RH would have to be maintained for long periods to reduce both D. farinae and D. pteronyssinus by desiccation procedures. The results of this study show that D. farinae and D. pteronyssinus have high reproductive potentials and population growth rates, which indicate that mite reduction procedures must be thorough or mite densities will return to high levels quickly following remediation if adequate food and suitable microclimatic conditions exist.

Drosophila pseudoobscura Frolova was found to lose weight at all water vapor activities (av) below saturation, suggesting that it is incapable of active sorption of water. Metabolic activity was the same at both 0.98 av and 0.50 av in dim light. Tritiated water was used to determine the rate of water exchange between the water pool of the fly and its environment. The rate constant for transpiration decreased as the water vapor activity of the environment decreased, indicating that D. pseudoobscura maintains a water balance by regulating water loss rather than water uptake. Sorption rate was propportional to the water vapor activity of the fly's environment. It is postulated that transpiration rate is regulated by the spiracular openings. Metabolic water constitutes a significant portion of the water transpired from the fly's water pool.

Partially dehydrated female house dust mites, Dermatophagoides farinae, regained water from unsaturated ambient air at 0.55 av (55% rh) and 15 °C, 0.65 av (65% rh) and 25 or 30 °C, and 0.75 av (75% rh) and 35 °C. Mites continued to lose water at each of the above temperatures when av was reduced 0.10 av (10% rh). The critical av for the temperature range 15–35 °C ranges between 0.55 and 0.75 av and is proportional to temperature. All mites died in less than 24 h at 40 °C and 0.85 or 0.95 av.

Duration of the life cycle at 16, 23, 30, and 35°C and fecundity at 23°C and 75% RH were determined for the American house dust mite, Dermatophagoides farinae Hughes. Lengths of the life cycles at 23 and 30°C were 35.6 ± 4.4 and 17.5 ± 1.2 d, respectively. Few eggs completed development to the adult stage at 16 and 35°C. At 23°C and 75% RH, the preoviposition period was 3.7 ± 1.1 d following emergence of the female from the tritonymph. The average reproductive period was 34.0 ± 10.7 d with a mean total of 65.5 ± 17.4 eggs produced per female. Female longevity after cessation of egg production was 63.3 ± 64.6 d.

This study found that = 1 life stage(s) of Sarcoptes scabiei (L.) was significantly attracted to the nitrogenous compounds, guanine, purine, adenine, allantoin, hypoxanthine, xanthine, uric acid, ammonium chloride, ammonium nitrate, and ammonium sulfate. Females and larvae responded to all compounds. Males responded to all compounds except purine and allantoin. Nymphs responded to all compounds except allantoin. Some specific concentrations of compounds attracted only 1 life stage but other concentrations attracted multiple life stages. Also, some life stages were attracted by multiple concentrations of a compound. The concentration that induced the greatest response by a particular life stage varied between life stages. Overall, greater percentages of females were attracted to the nitrogenous compounds than any other life stage. Females responded to more concentrations of a compound compared to other life stages. Males responded to fewer concentrations then immatures. In addition, all life stages of S. scabiei were significantly attracted to the phenolic compounds, 2,6-dichlorophenol, methyl salicylate, and 2-nitrophenol. Nymphs followed by females responded to the most concentrations. The results indicated that these nitrogenous wastes and phenolic compounds acted in a pheromone-like manner that induced assembly of these ectoparasitic mites.

The LT50's of Dermatophagoides farinae subjected 40% and 50% rh and 25°, 28°, 31° and 34°C ranged from 1.33 to 3.98 days. LT50's for females were higher than those for males. Males were more susceptible to dessication than females. LT50's for the females of D. farinae and D. pteronyssinus were obtained when exposed for 24 hr to 1%% or less diazinon, Dowco® 214, Kara thane®, Rabon®, Ronnel®, and Pentac®. Concentrations greater than 1% were required to obtain an LT50 using Abate®, allethrin, Butacide®, malathion, rotenone, and Tedion®.

Feeding rates of Dermatophagoides farinae and D. pteronyssinus are significantly higher at ambient water vapor activities (av's) above the critical equilibrium activity (CEA) than below it. The quantity of water obtained with equilibrated food at av's below the CEA is insignificant when compared to that exchanged by sorption and transpiration and is not sufficient for dust mites to maintain water balance. The CEA for feeding mites is identical to that for fasting mites. Considering all possible avenues of water gain by house dust mites for maintaining water balance, their primary source of water to sustain life is that gained by passive and active sorption from ambient water vapor.

This study examines the energy relationship between the host and the ectoparasitic mite Sarcoptes scabiei var. canis. Parasitized rabbits during the first 14-wk, post-initial infestation gained weight at approximately the same rate, but they consumed more food and water than uninfested control rabbits. During weeks 17–42 after the initial infestation, infestation levels increased until 10–30% of the body area was heavily parasitized. During this time, infested rabbits steadily lost weight even though there was no marked difference in food consumption between infested and control rabbits. Oxygen consumption rates were 0.00206 and 0.00076 µl O2/h/mite for female and male mites, respectively, at 75% RH and 34°C. Based on these rates, mite density on the host, and the infested host body surface area, the energy demand by the mites on a heavily parasitized host was insignificant relative to the metabolic rate of the host. Parasite energy demand was not responsible for the weight loss or reduced weight gains exhibited by the parasitized hosts. All of the infested rabbits became free of mites within 2 wk after treatment with an acaricide and rapidly regained the lost weight.

Sarcoptes scabiei var. canis were unable actively or passively to sorb sufficient water vapor from unsaturated air to compensate for water loss in spite of an active uptake mechanism. Maintenance of water balance in this mite is supported by its location at the dry stratum corneum–stratum lucidum and stratum granulosum interface by its ingestion of intercellular fluid that oozes into the burrow or around the mouth parts. Water loss rate constants for females were 20.6–23.8% h-1 (per hour) at 97% RH and ranged from 4.9 to 6.2% h-1 at 75 and 22% RH. Rate constants for uptake of tritiated water and approach of equilibrium tritiated body water content for males and females were independent of relative humidity and ranged from 8.55 to 12.4% h-1. Fast water loss and uptake rates, uptake rate constants independent of relative humidity, and the observation that isolated mites produce an external fluid secretion suggest that these mites actively gain water by ingesting a hygroscopic solution. However, this process is not adequate to fully compensate for water loss.

Unsuccessful attempted transfers of Sarcoptes scabiei var. canis from one host species to another indicate that permanent transfer does not occur readily, even among animals that may interact closely. Permanent infestations of S. scabiei var. canis could not be established on sheep, goat, calf, or cat hosts. However, permanent infestations were established on the laboratory rabbit, and temporary infestations lasted at least 10 wk on some other atypical hosts. Temporarily infested atypical hosts could serve as temporary reservoirs of S. scabiei for natural hosts. In behavioral-choice experiments, S. scabiei var. canis responded to odors of hosts on which it could not become established. These results indicate that host odor is not a factor that determines host specificity.

Respiratory data on single arthropods weighing less than 100 µg (wet wt) are difficult to obtain unless the Cartesian diver technique (Holter 1943, Kanungo 1965) or a Digital Electrolytic Microrespirometer (Dunkle and Strong 1971) is used. The Digital Electrolytic Microrespirometer is capable of detecting less than 0.01µl of consumed O2 hr-1 (Dunkle and Strong 1971). I have used the Cartesian diver technique (Kanungo 1965) to detect 0.001 µl of consumed O2 hr-1 mite-1 for house dust mites weighing approximately 12.5 µg (wet wt) (Arlian 1972). A most difficult process in connection with use of a Cartesian diver apparatus is construction of uniform divers.