The Use of Dried Bovine Hemoglobin and Plasma for Mass Rearing New World Screwworm.

The success of the Screwworm Eradication Program is due to continuous mass rearing and dispersal of large numbers of competitive sterile flies in the field. Spray-dried powders of whole bovine blood, chicken egg, and milk substitute constituted the nutritional components of the traditional artificial larval diet used for mass rearing New World Screwworm (NWS), Cochliomyia hominivorax (Coquerel), Diptera: Calliphoridae. However, due to shifting availability and increasing costs of diet ingredients, it is necessary to investigate alternative products for the diet. Recently, spray-dried whole bovine blood became unavailable for purchase in the quantities that the Screwworm Program requires and thus were obliged to purchase bovine blood subproducts. Previous research showed that bovine hemoglobin could be substituted for whole blood with good results in small trials. Here, we report results of NWS larval diets prepared with bovine blood subproducts, hemoglobin and plasma, in 20-liter trays used in mass rearing. Diets were prepared using three separate hemoglobin/plasma ratios. Though all three configurations of hemoglobin and plasma were successful in the larval diet, we found the diets containing 1.5% total plasma, as opposed to 0.5 and 1%, produced heavier larvae and pupae, and resulted in more pupae per unit of diet. Considering cost, we determined that the ideal ratio for the blood portion of the diet for mass rearing is 80% hemoglobin and 20% plasma.

Physical and Physiological Factors Influence Behavioral Responses of Cochliomyia macellaria (Diptera: Calliphoridae) to Synthetic Attractants.

Volatile chemicals from waste artificial larval media as well as from bovine blood inoculated with bacteria isolated from screwworm-infested wounds attract gravid females of Cochliomyia hominivorax Coquerel and Cochliomyia macellaria (F.). Chemicals identified from volatiles are dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol, and indole; a blend of these attracted females to oviposit. Present studies investigated the effectiveness of these compounds, either in a blend or individually as potential oviposition attractants. Tests were conducted to determine the effects of gender, ovarian age, and the color and type of substrates on attraction response and oviposition of C. macellaria adults. Results showed that substrates treated with dimethyl trisulfide (DMTS) alone or the five-compound blend alone attracted significantly more gravid females than other chemicals. Black substrates treated with DMTS attracted more gravid flies than did the yellow substrates. Yellow substrates treated with indole attracted more males and nongravid females. In oviposition tests, females deposited significantly more eggs on meat-based substrates than those without meat. These findings suggest that several factors have to be considered for developing an effective oviposition attractant that should include effectiveness of individual chemicals used, the ratio of the chemicals in a blend, and their concentrations. Also, an effective trap design will need to consider using suitable color which will selectively attract gravid females.

Bacterial Volatiles Attract Gravid Secondary Screwworms (Diptera: Calliphoridae).

Bovine blood inoculated and incubated with bacteria was tested to determine if secondary screwworm, Cochliomyia macellaria (F.), would be attracted to the incubated substrate for oviposition. Five species of bacteria, Klebsiella oxytoca (Flugge), Proteus mirabilis Hauser, Proteus vulgaris Hauser, Providencia rettgeri Hadley, Elkins and Caldwell, and Providencia stuartii Ewing, previously isolated from animal wounds infested by primary screwworms, Cochliomyia hominivorax (Coquerel), were used. Incubated substrates were tested in a two-choice cage bioassay to study landing response and oviposition by gravid C. macellaria. Significantly more flies landed on substrates containing P. mirabilis than on substrates with other species of bacteria. Klebsiella oxytoca-treated substrates attracted the least flies. Substrates containing bacteria incubated for 72 h attracted significantly more flies than those incubated for 24-, 48-, or 96-h period. In 3-h duration oviposition tests, substrates with P. rettgeri attracted significantly more flies to oviposit than the other four species. The most eggs were recorded when substrates treated with all five species of bacteria were offered for oviposition. It is likely that multiple active chemicals present in the volatiles from substrates treated with all five species result in greater response than those in a single species. At least 72-h incubation seems to be necessary to obtain the most active volatile chemicals. Results suggest that C. macellaria uses similar chemical cues as C. hominivorax from bacteria volatiles as oviposition attractant/stimulant.

Effects of New Dietary Ingredients Used in Artificial Diet for Screwworm Larvae (Diptera: Calliphoridae).

Spray-dried whole bovine blood, dry poultry egg, and a dry milk substitute are the constituents of the artificial diet currently used for mass rearing screwworm larvae, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae). Due to high cost and uncertainty of the commercial supply of spray-dried blood, research was conducted to identify alternative, locally available, inexpensive, dietary ingredients which could reduce cost of rearing and eliminate concerns of short supply. Experimental diets were prepared without blood component and with various ratios of bovine blood or blood cell product and defatted soy flour. Results indicate that spray-dried bovine blood can be replaced by a readily available and less expensive blood cell product. When the quantity of whole dried blood or blood cell component was reduced or removed completely from the diet, the larvae did not feed adequately, resulting in high mortality. Those larvae that survived produced pupae that were of unacceptable quality. When the milk product was replaced by soy flour, pupae were slightly smaller than those reared using the current diet; however, replacement of egg product with soy flour produced even smaller pupae. Longevity of adult flies that emerged from these small pupae was short and the females deposited few eggs. These results indicate that soy flour cannot replace the blood component from the diet, but can replace the milk product successfully. It is likely that some factor or a combination of factors in the blood act as feeding stimulants, without which larvae are unable to feed normally, resulting in high larval mortality.

Response of Lucilia sericata (Diptera: Calliphoridae) to Screwworm Oviposition Attractant.

The sheep blowfly, Lucilia sericata Meigen (Diptera: Calliphoridae), causes sheep myiasis in various parts of the world. Female flies are attracted to sheep following various olfactory cues emanating from the sheep's body, and oviposit on suitable substrates on sheep ultimately causing myiasis. Earlier workers attempted to reduce fly population in the field, with some success, using traps baited with various attractants. This research was conducted to determine if L. sericata would respond to a recently developed synthetic attractant that has attracted gravid screwworms, Cochliomyia hominivorax Coquerel, and stimulated them to oviposit. Results of the laboratory bioassays demonstrated that gravid females L. sericata were attracted to substrates treated with the synthetic screwworm attractant composed of five compounds--dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol, and indole. Tests with various combinations of these compounds suggest that the sulfur compounds and indole are the most important compounds to elicit attraction and stimulate oviposition, while phenol and p-cresol may have minor roles. Semiochemical baits based on these compounds may be useful in the field to trap gravid L. sericata.

Normal contact and friction of rubber with model randomly rough surfaces.

We report on normal contact and friction measurements of model multicontact interfaces formed between smooth surfaces and substrates textured with a statistical distribution of spherical micro-asperities. Contacts are either formed between a rigid textured lens and a smooth rubber, or a flat textured rubber and a smooth rigid lens. Measurements of the real area of contact A versus normal load P are performed by imaging the light transmitted at the microcontacts. For both interfaces, A(P) is found to be sub-linear with a power law behavior. Comparison with two multi-asperity contact models, which extend the Greenwood-Williamson (J. Greenwood and J. Williamson, Proc. Royal Soc. London Ser. A, 295, 300 (1966)) model by taking into account the elastic interaction between asperities at different length scales, is performed, and allows their validation for the first time. We find that long range elastic interactions arising from the curvature of the nominal surfaces are the main source of the non-linearity of A(P). At a shorter range, and except for very low pressures, the pressure dependence of both density and area of microcontacts remains well described by Greenwood-Williamson's model, which neglects any interaction between asperities. In addition, in steady sliding, friction measurements reveal that the mean shear stress at the scale of the asperities is systematically larger than that found for a macroscopic contact between a smooth lens and a rubber. This suggests that frictional stresses measured at macroscopic length scales may not be simply transposed to microscopic multicontact interfaces.

Volatiles from waste larval rearing media attract gravid screwworm flies (Diptera: Calliphoridae) to oviposit.

Gravid screwworm flies, Cochliomyia hominivorax (Coquerel), are attracted to the volatiles from waste larval rearing media to deposit eggs. Studies were conducted to identify volatile chemicals from the waste larval media and determine their effectiveness to attract gravid flies to oviposit. Volatiles were collected using solid-phase microextraction method, and five active chemicals, namely, dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol, and indole, were identified using gas chromatography-mass spectrometry. In electroantennography studies, antennae ofgravid screwworm flies, Cochliomyia macellaria (F.), responded positively to each of the identified compounds. A synthetic blend of these five compounds in the ratio of 335:200:57:1:12 was prepared and tested for its effectiveness to attract both C. hominivorax and C. macellaria using laboratory bioassay methods. Significantly more gravid C. macellaria were attracted to and landed on substrates treated with 10-fold diluted blends compared with those landed on substrates treated with ethanol only (as control). Only a few young females and young and old males were attracted to the substrates treated with the synthetic blend. The C. hominivorax females laid significantly more eggs on substrates treated with waste media, 10-fold diluted blend, and 100-fold diluted blend than on substrates with undiluted blend or ethanol. Similarly, C. macellaria deposited significantly more eggs on substrates treated with waste media, 10-fold diluted blend, and 100-fold diluted blend compared with substrates with undiluted blend or ethanol. C. macellaria females deposited significantly less amount of eggs than did C. hominivorax females. These results indicate that the synthetic blend of five compounds identified may serve as an oviposition attractant for C. hominivorax as well as for C. macellaria.

An artificial diet for rearing Cochliomyia macellaria (Diptera: Calliphoridae).

Larvae of the secondary screwworm, Cochliomyia macellaria (F.), feed on carrion and may sometimes cause animal myiasis. They have been reared in the laboratory on various animal tissues to study their growth and development because of their importance in forensic science. We use secondary screwworms in our laboratory for preliminary experiments as a model for the primary screwworm, Cochliomyia hominivorax (Coquerel), which has been eradicated from the United States. C. macellaria larvae reared on animal tissues produced a putrid odor, an unfavorable condition in the laboratory, and variable pupal size and weight, bringing into question the validity of use as a model for C. hominivorax. Therefore, studies were conducted to develop a less odiferous artificial diet with reduced variability in resulting pupae by comparing three diets: 1) an artificial diet prepared from spray-dried blood, spray-dried poultry egg, dry milk substitute, and solidified with a polyacrylate polymer gel; 2) a fresh blood-based diet prepared similarly, except fresh bovine blood was used in place of spray-dried blood; and 3) a beef liver diet. Data from seven life-history parameters of resulting insects were collected and analyzed. Larval and pupal weights of C. macellaria reared on both the dry and fresh blood-based diets were significantly higher than those reared on the liver diet. Numbers of pupae and percentage of adult emergence were also significantly higher from both dry blood and fresh blood-based diets than those reared on the liver diet. Female flies developing from larvae reared on dry and fresh blood-based diets laid significantly more eggs than females developing from larvae reared on the liver diet. Results show that C. macellaria larvae developed and grew normally in the dry and fresh blood-based diets, indicating that an artificial diet can effectively replace the liver diet commonly used for rearing C. macellaria.

Lean body mass-based levothyroxine replacement in young athyrotic patients with differentiated carcinoma of thyroid.

OBJECTIVE: The objective of this study was to optimize dose of levothyroxine (LT4) based on lean body mass (LBM) in young athyrotic patients with differentiated carcinoma of thyroid (DCT) which has not been properly addressed in Bangladesh before. MATERIALS AND METHODS: SIXTY PATIENTS WITH DCT (AGE, RANGE: 20-39 years) having total thyroidectomy followed by radioiodine ablative therapy (RIT) and 23 euthyroid volunteers were recruited. Clinical, biochemical parameters were obtained from all patients after 2 months of RIT and on LT4 replacement at a dose of 200 µg/day as first follow up visit and also from control subjects. Then 60 patients were divided into two groups consisting of 30 patients each. Patients of Group-I received LT4 replacement based on LBM measured by dual energy X-ray absorptiometry (DXA) and Group-II continued LT4 replacement in conventional dose. Patients of both groups were assessed again for same parameters at 6 to 12 months at the second visit. RESULTS: Optimized dose of LT4 based on LBM by DXA (131 ±23 µg/day) significantly reduced thyroid hormones and kept thyroid stimulating hormone (TSH) in expected levels in patients of Group-I at the second visit compared to patients of Group-II who continued conventional LT4 dose (200 µg/day). Hyperthyroid symptom scale (HSS) was significantly reduced to 2 ± 1 in patients of Group-I but not in patients of Group-II, HSS, 8 ±1 (P > 0.001). CONCLUSION: Optimization of LT4 dose based on LBM can avoid chronic exposure of mild excess of thyroid hormone in young patients with low risk DCT.

Feasibility of using a Caribbean screwworm for SIT campaigns in Brazil.

The screwworm, Cochliomyia hominivorax (Coquerel), remains one of the most damaging parasites of livestock in South America, causing millions of dollars in annual losses to producers. Recently, South American countries demonstrated interest in controlling this pest using the Sterile Insect Technique, and a pilot-project was conducted near the Brazil-Uruguay border in 2009. Since molecular studies have suggested the existence of C. hominivorax regional groups, crossing tests were conducted to evaluate mating competitiveness, mating preference and reproductive compatibility between a C. hominivorax strain from the Caribbean (Jamaica-06) and one from Brazil. Mating rates between Jamaican males and Brazilian females ranged between 82 and 100%, and each male inseminated from 3.3 to 3.95 females. Sterile males, regardless of the strain, competed equally against the fertile males for Brazilian females. Jamaican sterile males and Brazilian fertile males mated randomly with fertile or sterile females. No evidence of genetic incompatibility or hybrid dysgenesis was found in the hybridization crosses. Mating barriers should not compromise the use of Jamaican sterile males for Sterile Insect Technique campaigns in Brazil.

Noise-activated dissociation of soft elastic contacts.

Adhesive forces are capable of deforming a soft elastic object when it comes in contact with a flat rigid substrate. The contact is in stable equilibrium if the total energy of the system arising from the elastic and surface forces exhibits a minimum at a zero or at a slightly negative load. However, as the system is continually unloaded, the energy barrier decreases and it eventually disappears, thus leading to a ballistic separation of the contact. While this type of contact splitting has received wide recognition, what has not been much appreciated with these types of soft adhesion problems is that rupture of a contact can also occur at any finite sub critical load in the presence of a noise. The soft contact problems are unique in that the noise can be athermal, whereas the metastable and stable states of the thermodynamic potential can arise from the competition of the elastic and the interfacial energies of the system. Analysis based on Kramers' theory and simulations based on Langevin dynamics show that the contact rupture dynamics is amenable to an Eyring's form of a force and noise-induced escape of a particle from a potential well that is generic to various types of colloidal and macromolecular processes. These ideas are useful in understanding the results of a recent experiment involving the noise-activated rolling dynamics of a rigid sphere on a surface, where it is pinned by soft micro-fibrillar contacts.

Vibration spectroscopy of a sessile drop and its contact line.

Resonance frequencies of small sessile liquid drops (1-20 µL) were estimated from the power spectra of their height fluctuations after subjecting them to white noise vibration. Various resonance modes could be identified with this method as a function of the mass of the drop. Studies with water drops on such supports as polystyrene (θ ≈ 80°) and a superhydrophobic surface of microfibrillar silicone rubber (θ ≈ 162°) demonstrated that the resonant frequency decreases with the contact angle, θ. This trend is in remarkable agreement with the current models of the resonant vibration of sessile drops. A novel aspect of this study is the analysis of the modes of a slipping contact line that indicated that its higher frequency modes are more severely damped than its lower ones. Another case is with the glycerol-water solutions, where the resonance frequency decreases with the concentration of glycerol purely due to the capillary effects. The interface fluctuation, on the other hand, is strongly correlated with the kinematic viscosity of the liquid. Thus, these experiments provide a means to measure the surface tension and the viscosity of very small droplets.

Random motion with interfacial contact: driven diffusion vis-à-vis mechanical activation.

Rolling of a small sphere on a patterned support of an elastomer is governed by a non-linear friction. No motion occurs when the external field is weaker than the frictional resistance. However, with the intervention of an external noise, a viscous friction like behavior emerges; thus the sphere rolls with a uniform drift velocity that is proportional to the applied field. At a very low noise strength, the sphere exhibits a stick-slip behavior with motion occurring always along the bias. With the increase in the noise strength, the sphere exhibits a diffusive drift accompanied with forward and backward displacements. During this stage of driven diffusive motion, the ratio of the integrated probabilities of the negative-to-positive work fluctuations decreases monotonically with the time of observation, from which a temperature like intensive parameter can be estimated. This parameter conforms to Einstein's ratio of diffusivity and mobility that increases almost linearly, even though the diffusivity increases super-linearly, with the strength of the noise. A new barrier crossing experiment is introduced that can be performed either with a hard (e.g. a steel ball) or with a soft (e.g. a water drop) sphere in contact with a periodically undulated substrate. The frequency of barrier crossing follows a transition state equation allowing a direct estimation of the effective temperature. These experiments as well as certain numerical simulations suggest that the effective temperature of a system controlled by a non-linear friction may not have a unique value.

Evaluation of artificial larval rearing media waste as oviposition attractant for New World screwworms (Diptera: Calliphoridae).

The waste artificial larval rearing media of New World screwworms, Cochliomyia hominivorax (Coquerel) were evaluated to determine their effectiveness as oviposition attractants. Various concentrations of waste larval media resulting from rearing screwworm larvae in gel and cellulose fiber-based artificial diets tested over a 4-wk period attracted varying number of gravid screwworm flies to oviposit. Three-day-old waste medium with concentrations of 10 and 25% were most attractive to gravid female flies for oviposition and resulted in the most oviposition. One and 7-d-old wastes at all concentrations were less attractive for oviposition than the 3d-old media. The fresh (0-d-old), 14-d- and 28-d-old waste media were the least attractive substrates for oviposition. The waste from the cellulose fiber-based diet resulted in significantly more oviposition compared with waste from the gel-based diet. Microorganisms growing in the waste media probably produce metabolites that attract gravid screwworm flies to oviposit. Use of the waste products of appropriate age and dilution as oviposition substrates would enhance oviposition in mass production colony cages.

Persistent regional variation in treatment of hypertension.

OBJECTIVES: To assess regional variation within England in the proportion of people with survey-defined hypertension who were on treatment, and hypothesize if this was due to chance or confounding. STUDY DESIGN: Data from three annual, cross-sectional health examination surveys, the Health Survey for England. METHODS: Nationally representative random samples of the free-living general population were visited by an interviewer and a nurse. Blood pressure was measured with an automated monitor using a standardized protocol (2005: n = 5321, 2006: n = 10,213, 2007: n = 4848). Hypertension was defined as systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg, and/or taking prescribed medication to lower blood pressure. RESULTS: In London, a higher proportion of participants with survey-defined hypertension were on anti-hypertensive medication in each separate year's sample compared with the rest of England [2005-2007 average: 61% men, 66% women in London; 43% men, 55% women in England (P for London vs rest of England <0.001 for each sex)]. Regression analysis showed that this regional effect [odds ratio (OR) 1.47 95% confidence interval (CI) 1.94-2.47, P = 0.031] was no longer significant after adjustment for demographic and socio-economic factors (OR 1.37, 95% CI 0.94-1.98, P = 0.101), but was strengthened (OR 1.69, 95% CI 1.09-2.60, P = 0.018) by including longstanding illness, diabetes, cardiovascular disease and health behaviours in the model. CONCLUSIONS: The proportion of hypertensive patients on anti-hypertensive medication was consistently above the national average in London, and this was associated with personal characteristics. Comorbidities increased the effect, even after adjustment for personal characteristics. This result may be due to greater population mobility in London, with more people having new patient health checks. Understanding this variation could enhance treatment nationally and internationally.

Stochastic rolling of a rigid sphere in weak adhesive contact with a soft substrate.

We study the rolling motion of a small solid sphere on a fibrillated rubber substrate in an external field in the presence of a Gaussian noise. From the nature of the drift and the evolution of the displacement fluctuation of the ball, it is evident that the rolling is controlled by a complex non-linear friction at a low velocity and a low noise strength (K), but by a linear kinematic friction at a high velocity and a high noise strength. This transition from a non-linear to a linear friction control of motion can be discerned from another experiment in which the ball is subjected to a periodic asymmetric vibration in conjunction with a random noise. Here, as opposed to that of a fixed external force, the rolling velocity decreases with the strength of the noise suggesting a progressive fluidization of the interface. A state (K) and rate (V) dependent friction model is able to explain both the evolution of the displacement fluctuation as well as the sigmoidal variation of the drift velocity with K. This research sets the stage for studying friction in a new way, in which it is submitted to a noise and then its dynamic response is studied using the tools of statistical mechanics. Although more works would be needed for a fuller realization of the above-stated goal, this approach has the potential to complement direct measurements of friction over several decades of velocities and other state variables. It is striking that the non-Gaussian displacement statistics as observed with the stochastic rolling is similar to that of a colloidal particle undergoing Brownian motion in contact with a soft microtubule.

Solidifying agent and processing of blood used for the larval diet affect screwworm (Diptera: Calliphoridae) life-history parameters.

Spray-dried whole bovine blood and a sodium polyacrylate polymer gel as a bulking and solidifying agent are among the constituents of the current larval diet for mass rearing screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae). Locally available, inexpensive dietary materials could reduce rearing cost and address an uncertain commercial supply of spray-dried blood. We compared efficacy of diet prepared from fresh bovine blood after decoagulation with sodium citrate or ethylenediaminetetraacetic acid (EDTA) or after mechanical defibrination, with the diet containing spray-dried blood using either gel or cellulose fiber as the bulking and solidifying agent. Several life-history parameters were compared among insects reared on each of the blood and bulking agent diets combination. Diets containing citrated blood yielded the lightest larval and pupal weights and fewest pupae. EDTA-treated blood with the gel also caused reductions. EDTA-treated blood with fiber yielded screwworms that were heavier and more numerous than those from the diet with citrated blood but lighter than those from the control diet using spray-dried blood. A reduction in percentage of adults emerging from pupae occurred from diets with both bulking agents using citrated blood and the diet using EDTA mixed with the gel bulking agent. As a group, the cellulose-fiber diets performed better than the gel diets. Larval diet did not affect adult longevity, weight of the eggs deposited by the females that emerged or subsequent egg hatch. Parameter measurements of insects from both defibrinated blood diets were similar to those from the spray-dried blood diets, indicating that fresh, defibrinated bovine blood can successfully replace the dry blood in the screwworm rearing medium.

Volatiles emitted from eight wound-isolated bacteria differentially attract gravid screwworms (Diptera: Calliphoridae) to oviposit.

Bovine blood inoculated with bacteria isolated from screwworm [Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae)]-infested animal wounds was tested as an attractant for oviposition for gravid screwworms. Eight species of gram-negative coliform (Enterobacteriaceae) bacteria mixed with bovine blood singly or all species combined and incubated for various times produced volatiles that attracted gravid flies in a cage bioassay in varying numbers. In 15-min duration tests, volatiles from five species of bacteria (Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, and Providencia stuartii) attracted more females than volatiles of the three species (Enterobacter cloacae, Enterobacter sakazakii, and Serratia liquefaciens). In 1-h duration oviposition tests, volatiles from the substrate using the same five species of bacteria attracted more females to oviposit than the other three species. Volatiles from 24-h incubation period elicited least attraction and oviposition whereas volatiles from the 48- and 72-h incubation period resulted in significantly more attraction and oviposition. Attraction and oviposition decreased significantly when the substrates were incubated for 96 h. Volatiles from substrate with all species of bacteria combined attracted a significantly higher percentage of flies to land and oviposit than those from substrates prepared with single species. It is possible that multiple active chemicals present in volatiles of the all-species substrate may act as synergists resulting in greater response than those observed with volatiles from single-species substrate. Before oviposition flies took a bloodmeal from the oviposition substrate. It is possible that the oviposition is moderated by two different factors in screwworm-first, by using a chemical cue to land on a potential oviposition site and second, by using a bloodmeal to stimulate oviposition.

Experimental investigation of the drift and diffusion of small objects on a surface subjected to a bias and an external white noise: roles of coulombic friction and hysteresis.

We study the stochastic motion of a small solid block or a small water drop on a flat solid support in the presence of an external noise and a bias. The bias is caused either by inclining the plane of the support, as is the case with the solid block, or by creating a gradient of wettability, as is the case with a water drop. Both the solid block and the water drop exhibit drifted Brownian-like motion. There are, however, differences between the motion described here and that of a classical drifted Brownian motion, in that the Coulombic friction (for solid on solid) or wetting hysteresis (for water drops on a solid) accounts for a significant resistance to motion in addition to the kinematic friction. Although the displacement distribution here is non-Gaussian, the variance of the distribution increases with time, indicating that the overall motion follows simple diffusion. The diffusivity and the mobility of the solid object are considerably lower than the values expected when the diffusion is governed by only kinematic friction. The experimental diffusivity increases with the power of the noise with an exponent of 1.61, which is close to that (1.74) of an analysis based on the Langevin equation when the Coulombic friction is taken into account in addition to the kinematic friction. The ratio of diffusivity and mobility increases slightly sublinearly with the power of the noise with an exponent of about 0.8. The experimentally observed relaxation time of the process is, however, considerably smaller than the Langevin relaxation time. When the experimental ratio of diffusivity and mobility is taken into account in the distribution function of the displacement, the later quantity becomes amenable to an analysis that is similar to the conventional fluctuation relations.

Diet pH, and viscosity affect development and survival of screwworm larvae (Diptera: Calliphoridae).

The effects of dietary pH and viscosity on larval development of the New World screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), were studied in the laboratory using a gel-based and a cellulose fiber-based media. The mean initial pH of the standard gelled diet was lower (6.5 +/- 0.3) than that of the standard cellulose fiber-based diet (6.8 +/- 0.6). As larval development progressed, these values decreased to below 6.0 possibly due to the accumulation of acidic metabolic waste. Diets formulated with higher initial pH (7.5) produced a slightly larger and greater number of pupae compared with those for untreated standard diets. The diets with lower than normal initial pH (4.0) produced significantly smaller and lower numbers of pupae compared with those produced by the untreated standard diets. The effects of viscosity were studied using the cellulose fiber-based diet at six different initial viscosity levels ranging from 2,000 to 7,000 cP. The viscosity level of the diet increased as the larval development progressed due to gradual loss of moisture from the diet. The diet viscosity levels of 4,000 and 5,000 cP proved superior for larval development showing significantly higher yield and larger pupae compared with those obtained from diets with initial viscosities of 2,000-3,000 or 6,000-7,000 cP. The cellulose fiber-based diet used for mass rearing should be formulated to an initial viscosity reading of 4,000-5,000 cP for optimal larval growth and development. Adoption of a diet formulated to provide a higher initial pH such as 7.5 may produce better quality insects.