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The effects of varying densities of lone star tick, Amblyomma americanurn (L.), on measured physiological parameters of beef cattle in a controlled environment was determined. Steers were infested with either 0, 20, 60, or 120 pairs of adult ticks. Heart rate, respiration, rectal temperature, fecal and urine excretions, and water and feed consumption were monitored daily. Blood samples were taken every 3rd d to measure cortisol, total proteins, urea nitrogen, and glucose levels. Hematocrits were also taken at each blood sampling. Results showed that A. americanum evoked elevated heart rates. The other measured physiological and nutritional responses of parasitized steers were similar to the control steers. These results suggest that tick densities were too low to cause physiological stress under the conditions used in this study. The methodology precluded detection of the parameters measured, A. americanum does not affect the parameters measured, or that fluctuating environmental parameters and varying host nutritional states may play major roles in modulating the effect of A. americanum infestations on cattle in nature.

The underlying mechanism responsible for enhanced toxicity of the organophosphate diazinon in eight pyrethroid-resistant horn fly, Haematohia irritans (L.), field populations was investigated. In vitro enzyme assays and in vivo pyrethroid synergist studies showed increased activity of the mixed function oxidase system (measured as O -demethylase activity) in five of the eight populations with, in most instances, a subsequent increase in diazinon metabolism. We suspect that enhanced toxicity of diazinon (or negative cross-resistance), as observed in pyrethroid-resistant horn fly field populations, may result from in vivo accumulation of the toxic metabolite diazoxon.

This study was conducted to determine the inherent variability of insecticide-treated glass tubes and filter paper disks, two methods currently being used to measure insecticide resistance in adult horn fly, Haematobia irritans (L.), populations. Flies were exposed to glass or filter paper surfaces treated with an LC50 concentration of permethrin, fenvalerate, diazinon, or pirimiphos methyl. Mortality was determined by five or six individuals. In all cases, there was a significant difference among surfaces treated with the same insecticide, and there was a significant difference in the horn fly mortality recorded by different individuals. These results suggest that testing wild horn fly populations of mixed ages for insecticide resistance May only represent an indication of resistance in the population. The observed variability among individuals reinforces the dogma that one person should be responsible for data collection during experimental procedures.

Dose-mortality data from 40 horn fly, Haematobia irritans (L.), populations revealed that susceptibility to permethrin and diazinon was negatively correlated (i.e., as susceptibility to permethrin decreased, toxicity of diazinon increased). Permethrin-resistant horn fly populations exposed for 18 wk to cattle tagged with ear tags impregnated with 20% (AI) diazinon resulted in a 2- to 6-fold reduction in this resistance. These populations also had LC50s for diazinon that were two to five times lower than those of populations susceptible to permethrin. Frequency of homozygous permethrin-resistant individuals decreased as much as 57% after exposure to diazinon during this period.

Ear tags impregnated with a mixture of cyhalothrin-piperonyl but oxide-DEF (S,S,S,-tributyl phosphorotrithiolate) or cypermethrin-piperonyl butoxide-chlorpyrifos were evaluated for the management of pyrethroid-resistant horn flies, Haematobia irritans (L.), on cattle in Kentucky. At the time of treatment, all horn fly populations were resistant to the pyrethroids in these mixtures. Although acceptable control of horn flies (average > 92%) was generally achieved on treated animals, LC50s for the pyrethroid mixture tested on each population were 2-33 times greater after 14 wk exposure compared with values before treatment. At the end of this exposure period, the frequency of pyrethroid-resistant individuals remaining in each of the treated horn fly populations was 100%.

Physiological and nutritional responses were measured in beef steers exposed to laboratory infestations of stable flies, Stomoxys calcitrans (L.). Calves (n = 6 per treatment) were infested with four levels of stable flies for three periods daily (15 min each period) for 14 d. Steers exposed to 0, 10, 20, or 30 stable flies consumed similar amounts of feed and water; they excreted similar amounts of feces and urine throughout the study. During the experiment, changes in body weight were not influenced by treatment. Heart and respiration rates, rectal temperatures, and circulating cortisol concentrations were similar among groups. Finally, nitrogen consumed, nitrogen lost in feces and urine, and nitrogen retained were unaffected by treatment. We suggest that intermittent exposure to these levels of stable flies, under the conditions of this study, does not evoke physiological and nutritional responses in beef steers.

Slow release formulations of 375, 750, and 1,125 mg (AI) in 50-g boluses and a subcutaneous injectable formulation (0.2 mg AI/kg body wt) of moxidectin (CL301423) were tested for the control of the little blue cattle louse, Solenoptes capillatus (Enderlein), and the cattle biting louse, Bovicola bovis (L). S. capillatus populations were reduced 4 wk after treatment and complete control was observed 6 wk after treatment in groups treated with boluses, B. bovis were first observed at 3 wk and continued to increase throughout the 14-wk test period. These were experimental boluses and future boluses may perform differently. Subcutaneous injections of moxidectin gave complete control of S. capillatus for a 27-d test period. Feces from animals treated with boluses were tested with face fly larvae, Musca autumnalis De Geer, to demonstrate fecal activity of moxidectin. Larval mortality in these groups ranged from 90 to 30% from 2 d to 10 wk after treatment.

The effect of previous insecticide use patterns for horn fly control on the susceptibility spectrum of horn fly (Haematobia irritans [L.]) populations from Kentucky and Arkansas is described. Populations of horn flies from both states were tested with three pyrethroids (cyhalothrin, cypermethrin, and permethrin), three organophosphates (diazinon, pirimiphos methyl, and tetrachlorvinphos), and a chlorinated hydrocarbon (methoxychlor). Dose-mortality data indicated insecticide resistance in Arkansas and Kentucky. Two permethrin-resistant horn fly populations in Kentucky that did not have a history of exposure to methoxychlor were cross-resistant to this chlorinated hydrocarbon. Horn fly populations from both states with a history of at least three consecutive years of exposure to various pyrethroid ear tags were subsequently exposed to cattle tagged with cyhalothrin-impregnated ear tags for 15-16 wk. Such exposure resulted in a decrease in susceptibility to this pyrethroid (ranging from approximately 30 to greater than 100-fold) when compared with levels before treatment. Horn fly populations from Arkansas resistant to cyhalothrin (as a result of exposure to cyhalothrin ear tags) were cross-resistant to pirimiphos methyl. Seasonal exposure of an Arkansas and Kentucky horn fly population to cattle with ear tags impregnated with pirimiphos methyl resulted in a significant decrease in susceptibility to this organophosphate.

A 1.0% liquid bait formulation of erythrosin B was tested for house fly, Musca domestica L., control in one room of an environmentally controlled caged-layer poultry facility. Reduced fly numbers were recorded between day 14 and day 17 in the room treated with erythrosin B, after 17 d populations increased significantly in treatment and control rooms. Increasing the light intensity to 188 or 386 lm/m squared for 8 h a day or increasing bait stations from one station per 87 m3 to one station per 70 m2 had no effect on developing house fly populations. Annoying levels of a vinegar fly, Drosophila robusta group, developed in the poultry facility during the study. Populations increased to greater than 400 adults/m2 of wall surface by day 15, then declined in the treatment room to less than 1 adult/m2 by day 33. Mortality of house flies that had ingested a 1.0% liquid formulation of erythrosin B was recorded under laboratory light intensities of 51, 532, and 1,030 lm/m2. All three intensities resulted in mortality significantly higher than the control, but mortality among the light intensity treatments did not differ significantly. When house flies were supplied water with erythrosin B, mortality did not differ significantly from that of the control.

Specific physiological and nutritional responses of beef steers to laboratory infestations of horn flies, Haematoma irritans (L.), were measured. Indicators of physiological stress were changes in heart rate, respiration rate, and rectal temperature. Blood cholinesterase, cortisol, creatine phosphokinase, glucose, hemoglobin, lactic dehydrogenase, packed cell volume, total protein, urea nitrogen, and white cell count were measured to assess metabolic changes in response to fly infestation. Dry matter and nitrogen digestibilities and nitrogen retention were used as indices of feed utilization. Beef steers exposed to 100 or 500 horn flies per head had significantly increased heart rates, respiration rates, and rectal temperatures. In addition, water consumption and urine production were significantly increased after exposure of steers to 500 horn flies per head. Urinary nitrogen excretion was significantly increased when steers were exposed to 500 horn flies per head and the value for steers exposed to 100 horn flies was intermediate between these and control steers. Dry matter digestibility and nitrogen digestibility did not differ significantly among treatments, but nitrogen retention was significantly reduced in both fly-infested groups. Blood cortisol concentrations were significantly increased on day 1 in steers exposed to 500 horn flies per head, and were numerically higher on most sampling days at both levels of fly infestation. Higher cortisol levels, combined with increased body temperatures and steer activity, contributed to reduced nitrogen retention in steers exposed to horn flies. No significant difference existed among treatments in levels of other blood components measured and all values were within ranges considered normal.

The effect of recommended dosages of trichlorfon, fenthion, famphur, and phosmet on physiological and nutritional indices of steers infested and not infested with Hypoderma spp. were evaluated under laboratory conditions. The parameters used as indicators of general stress were heart and respiration rate, rectal temperature, blood cholinesterase, blood urea nitrogen, serum glutamic oxalacetic transaminase, serum creatine phosphokinase and packed cell volume. Feed utilization indices included dry matter and nitrogen digestibilities. Heart rates, respiration rates, and rectal temperatures increased rapidly after treatment of grub-free steers and returned to normal within 3 h after treatment. Treatments of grub-infested steers with trichlorfon and phosmet resulted in significantly increased respiration rates, and rectal temperatures were significantly increased after exposure to trichlorfon, phosmet, and fenthion. Treatment with phosmet significantly reduced heart rates through 1 week after treatment. Blood cholinesterase levels were decreased after all treatments and blood urea nitrogen was significantly lowered after treatments with trichlorfon, famphur, and phosmet.

Dow ET-57 in a bolus and as an additive in a feed formulation was tested in the fall of 1956 against cattle grubs, Hypoderma spp. Four hundred seventy-nine Hereford steers and heifers were used, of which 235 head were located at the Fort Hays Branch Agricultural Experiment Station, Hays, Kansas, and 244 head were located at the Gooch Mills Juniata Experimental Ranch, Manhattan, Kansas. All treated animals were given 110 mg. of Dow ET-57/kg. of body weight. There were no consistent differences in gains in weight of the treated and untreated animals. Grub counts were made monthly or every 28 days in accordance with the cooperator’s weighing schedule and showed a significant decrease in the number of grubs in the treated animals. At the Fort Hays Branch station, 118 animals were treated with boluses and showed an average increase of 0.5 grub per animal. The 117 untreated animals showed an average increase of 11 grubs per animal. At the Juniata ranch, 80 head were bolused and showed an average increase of 0.38 grub per animal. Another 80 animals were treated by adding the insecticide to the feed and showed an average increase of 0.25 grub per animal. The 84 untreated animals showed an average increase of 3.2 grubs per animal. Blood cholinesterase investigations were conducted on 30 animals, 10 of which were treated with boluses, 10 were treated by feed and 10 were used as controls, and showed that Dow ET-57 produced a marked depression of enzyme activity. Toxic symptoms were not observed in any of the experimental animals.

Objectives were to: (1) find systemic compounds which, when given orally to rats, kill oriental rat fleas, Xenopsylla cheopis (Rothschild); (2) determine the lowest dosage level to produce a significant mortality of fleas; and (3) determine the duration of systemic effectiveness. Nine of the 21 compounds evaluated produced more than 50% mortality of fleas. Five were subjected to more extensive studies: dimethoate, Bayer 29493 ( O, O -dimethyl O -[4(methylthio)-m-tolyl]phosphorothioate), American Cyanamid CL 38064 (phosphorothioic acid, O-p -(ethylsulfamoyl) phenyl O, O -dimethyl ester), American Cyanamid CI 38023 (phosphorothioic acid, O, O -dimethyl O-p -(dimethylsulfamoyl)-phenol ester), and Dylox® ( O, O -dimethyl-2,2,2-trichloro-1-hydroxyethyl phosphonate). Each of the 5 compounds, except Dylox, was used in two experiments. The first consisted of confining fleas on dosed rats: (1) one hour after dosing and permitting them to feed for 3 hours; (2) four hours after dosing and permitting them to feed for 8 hours; and (3) twelve hours after dosing and permitting them to feed for 12 hours. The second experiment consisted of confining fleas on dosed rats for a 3-hour feeding period after delays between dosages and opportunity for initial feeding of 1, 4, 7 and 10 hours; mortality at 13 hours after dosing was determined following a feeding period of 11 hours. Dimethoate at 50 mg./kg. produced a high mortality of fleas following a 1-hour delay between dosing and feeding but all effectiveness had dissipated by 4 hours following dosing. Bayer 29493 produced a high mortality of fleas at 75-150 mg./kg. after a 1-hour delayed feeding period and retained relative effectiveness for a period exceeded only by CL 38064 and about equal to CL 38023.

Adult Musca autumnalis DeGeer exposed to surfaces treated with 0.025, 0.05, and 0.075 mg of penfluron or BAY SIR 8514 (2-chloro-N-[[[4-(trifluromethoxy)phenyl] amino] carbonyl] benzamide) per cm2 for 1, 3, or 6 h were evaluated for treatment effect on egg hatch and F1 larval mortality. Inhibition of egg hatch and F1 larval mortality were dependent on exposure time, concentration, mating regime, and elapsed time after exposure. Exposed female flies mated with untreated males demonstrated more greatly inhibited egg hatch than exposed male flies mated with untreated females. A greater inhibition of egg hatch resulted when exposed females and males were mated to each other. Inhibition of egg hatch decreased as the flies aged. Both compounds demonstrated a greater mortality against F1 face fly larvae than against egg hatch.

Diazinon, azinphosmethyl, malathion, and methoxychlor malathion, and methoxychlor applied in 3-gal total volume were evaluated for effectiveness against alfalfa weevil (at rates of 0.5, 1, and lib/acre, respectively) were as Hypem postica (Gyllenhal) when applied by aircraft at effective as a methoxychlor (1-lb rate) standard applied various rates and formulations. Undiluted technical for by conventional ground equipment in 20-gal total volume mulations of diazinon (0.59 and 1.06 Ib active/acre) and per acre. Effective adult weevil control was observed in malathion (1.14 and 1.73 Ib actual/acre) gave effective fields treated with 0.38 Ib actual azinphosmethyl applied control when applied late in the spring, azinphosmethyl, undiluted after first harvest.

Two formulations of ronnel, 5.5% ronnel mineral granules and 5.5% ronnel mineral block, were given free choice to Charolais cows, calves, and heifers for control of face fly, Musca autumnalis DeGeer; horn fly, Haematobia irritans (L.); and cattle grub, Hypoderma (spp.). The 5.5% ronnel mineral block was also tested in conjunction with a combination face rubber and mineral feeder. The face rubber was treated with 1% ronnel in no. 2 fuel oil. Good horn fly reduction occurred in all tests, whereas face fly reduction was negligible in 2 of 3 tests. Face fly reduction was greatest on the cattle having access to the face rubber. Bioassay of composite fecal sample with face fly larvae indicated that the manure was completely unsuitable for larval development. However, inspection of individual dung piles in the field showed relatively poor control of face fly larvae. Cattle grub control was essentially 100%. The cows and calves having access to the blocks consumed more ronnel mineral than cows and calves having access to the granular form. Open heifers consumed more ronnel mineral block than the cows and calves on either formulation.

A 5-year survey was conducted to determine the natural incidence and intensity of infestation by the larva of sheep botfly, Oestrus ovis L., in Kentucky sheep. Maximum infestation by 1st-instar larvae occulted during November, while the 2nd- and 3rd-instar larvae were most numerous during July. More than 90% of the inspected sheep were infested during the months of October through February.

Atherigona soccata Rondani has become the main pest of sorghum in Thailand. Attempts in previous years to control this insect with available insecticides failed. Carbofuran as a seed treatment at a rate of 2, 3, 4, or 5% AI/weight of seed and also as a soil treatment at planting time at a rate of 1 to 3 kg/ha gave good control. Aldicarb granules applied to the soil at a rate of 2 kg/ha gave satisfactory control at Pakchong but not at Tha Phra. Granular monocrotophos applied as a soil treatment was ineffective in reducing shoot fly infestation. Azinphosmethyl was slightly more effective than Dursban® ( O, O -diethyl O -(3,5,6-trichloro-2-pyridyl) phosphorothioate) in controlling the shoot fly, when both materials were applied as 0.1% foliage sprays at 3-day intervals.

Pastured steer calves on a hay diet were given 0, 0.5, 1, and 2% coumaphos salt, free choice, for 205 days, then 0 and 2% coumaphos salt for 146 additional days. Observations were made for any adverse effects that may have been caused by the treatment plus any effect the treatments had on parasite control. Very poor control of cattle grubs and no control of lice or internal parasites resulted in all the treatments. Salt consumption increased as the concentration of coumaphos was increased, and over a 205-day winter test the animals on the 0.5, 1, and 2% coumaphos salt consumed an average of 78, 190, and 390 rag of actual coumaphos/head/day, respectively. The animals that were continued on the 2% coumaphos salt consumed an average of 607 mg of actual coumaphos/head/day during the 146 days of the summer test and consumed an overall average of 487 mg/head/day for 351 days. All treated animals consumed more salt than the untreated. No significant differences were found in weight gains among the treated animals during the winter test. A significant difference was found between winter and summer gains made by the animals on the 2% coumaphos salt. The untreated animals averaged 75 lb/head more during the summer than the treated, whereas during the winter the treated averaged 67 lb/head more than the untreated. Control of adult horn flies, Haematobia irritans (L.), and face flies, Musca autumnalis DeGeer, was erratic. Bioassay of feces collected from treated animals, however, showed 100% reduction of face flies whereas field observations of 2- to 3-day-old dung piles showed 79% reduction of face fly larval development.

Blood and cattle grubs from cattle treated with ronnel were analyzed for anticholinesterase metabolites by enzyme assay of intact paper chromatograms. Ronnel and its oxygen analog were detected in the blood while the cattle grubs contained ronnel and an unidentified anticholinesterase. The latter could be produced also in vitro by incubating ronnel with grub tissue. No oxygen analog could be detected in the grubs even though present concurrently in the blood of cattle receiving oral doses of ronnel at twice the recommended therapeutic rate. The possible role of the anticholinesterase in the systemic action of ronnel is as yet unknown

Ciodrin® ( alpha . methylbenzyl 3-hydroxycrotonate dimethyl phosphate) and dichlorvos were applied topically as oil and water treatments on horses to determine possible toxic effect. No clinical symptom of toxicity was seen in any of the horses. However there was inhibition of plasma CHE activity. None of the treatments was effective in reducing fecal strongyle egg counts.

Flies collected on two relatively isolated ranches near Ellsworth and Wilmore, Kan., 110 miles apart had virtually no insecticide resistance. Field collections were brought to the laboratory and daily records maintained of eggs laid, longevity, eggs hatched, resulting pupation, and resulting emergence. The Ellsworth f1ies, compared with the Wilmore flies, laid a substantially greater number of eggs earlier in life, except during the second and third days, principally because of (1) a greater number of eggs per female fly-day, but also because of (2) a greater survival of female parents earlier in life. But the Wilmore flies, eventually, almost caught up with the Ellsworth flies in egg production because of a substantially greater production of eggs per female fly-day later in life. Hatchability was less in the Ellsworth population early in life primarily because of a high percentage of hatch of the Wilmore eggs during the second and third days. Hatchability was greater in the Ellsworth flies later in life. Totals for the 27 days of the parents’ lives were not significantly different. Pupation of newly hatched larvae and emergence of pupae were lower in the Ellsworth population during the first two 9-day periods as well as for the entire 27-day period of the parents’ lives. The Ellsworth population produced 24.3 adult offspring per female parent as compared with 49.8 by the Wilmore population, primarily because of the relatively high adult survival, from egg to adult, of Wilmore eggs laid during the (1) second and third days and (2) during the 10- to 18-day period of the lives of the parents, which was when a substantial portion of the Wilmore eggs were produced.

Information on self-dusting stations and the efficacy of several different insecticides used therein for control of Haematobia irritans (L.) are presented. Several different dust bags which were placed in different situations were tested during the summer of 1965 and 1966. Dusts included 3% and 5% Rabon® (2-chloro-1-(2,4,5-trichlorophenyl) vinyl dimethyl phosphate), 5% coumaphos, 3% malathion, 5% ronnel, 5% fenthion, and 3% crotoxyphos. Out of 43 different tests, only one with 3% crotoxphos, two with 5% ronnel, and three with 3% malathion showed less than 90% effectiveness in reduction of the horn fly.

Specific physiological and nutritional responses of beef steers to combined infestations of horn flies, Haematobia irritans (L.), and stable flies, Stomoxys calcitrans (L.), were measured in the laboratory. Measurements used as indicators of physiological stress were changes in heart rate, respiration rate, and rectal temperature. Various blood components were measured to assess metabolic changes in response to fly infestation. Dry matter and nitrogen digestibility and nitrogen retention were used as indices of feed utilization. Beef steers exposed to 100 horn flies plus 25 stable flies or 500 horn flies plus 50 stable flies per head had significantly increased heart rates, respiration rates, and rectal temperatures. Dry matter and nitrogen digestibility did not differ significantly among treatments, but nitrogen retention was significantly reduced in both fly-infested groups. Blood cortisol concentrations were significantly increased on day 12 in steers exposed to 100 horn flies plus 25 stable flies per head and on days 1, 8, and 10 in steers exposed to 500 horn flies plus 50 stable flies per head. Higher cortisol levels, vital signs, and steer activity contributed to reduced nitrogen retention in steers exposed to horn flies plus stable flies. No significant difference existed among treatments in levels of other blood components, and all values were within ranges considered normal.

Research trials in California, Nebraska, and Kentucky have shown that an experimental paste containing levamisole at a constant rate and famphur at several rates will control both cattle grubs, Hypoderma lineatum (Villers) and Hypoderma bovis (L.), and gastrointestinal worms. A paste containing 11.5% levamisole (8 mg/kg body weight) and 21.6% famphur (30 mg/kg body weight) provided grub control equivalent to that of either famphur (Warbex) or ivermectin (Ivomec) and gastrointestinal worm control comparable with that of levamisole (Tramisol) or ivermectin.

Susceptibilities of laboratory-reared and field-collected Musca autumnalis L. to several pyrethroids (permethrin [Ectiban, Atroban], flucythrinate, fenvalerate, and cypermethrin), organophosphates (crotoxyphos, dichlorvos, tetrachlorvinphos, coumaphos, and malathion), chlorinated hydrocarbons (dioxathion, toxaphene, and methoxychlor), and the carbamate bendiocarb were compared. The homogeneous response of the field population to treatment with methoxychlor suggested resistance. The resistance index (LD50 field strain ÷ LD50 laboratory strain) for the field population treated with methoxychlor was 4.06; indices of the field population treated with the other insecticides ranged from 1.00 to 1.83.

Adult Musca domestica L. exposed to surfaces treated with 0.025, 0.05, 0.10, and 0.20 mg/cm2 of triflumuron for 1, 3, or 6 h were evaluated for effects on egg hatch and F, larval mortality. Inhibition of egg hatch and F1 larval mortality were dependent on exposure time, concentration, mating regime, and elapsed time after exposure. The effect of triflumuron was more pronounced in inhibiting egg hatch and producing mortality in the F1 larval stage when females or both sexes were exposed and mated together than when only males were exposed and mated to unexposed females. Inhibition of egg hatch and F1 larval mortality decreased as the flies aged.

Tagging of all beef cows and calves in a herd with one 8% fenvalerate ear tag per ear during early spring resulted in an average of 90% reduction of face flies, Musca autumnalis De Geer, over a 21-week period. In another test, tagging of lactating dairy cows with one tag per ear, with a portion of the herd left untagged during a 7-week period in the middle of the test, resulted in an average of 86% reduction of face flies over an 18-week period. Some repellancy of the face fly by the treatment was noticed. Seasonal control of the horn fly, Haematobia irritans (L.), was achieved in both treated herds, even when ca. one-third of the dairy cows were not tagged.

Larvae of the house fly, face fly, horn fly, and stable fly were reared in media containing various concentrations of L-canavanine. Response in order of decreasing sensitivity was the stable fly, face fly, horn fly, and house fly. Only 18% house fly mortality was obtained from 800 ppm canavanine, a level which killed at least 70% of the other 3 species. Horn fly and face fly showed additional delayed concentration-dependent effects expressed as smaller pupal size, some degree of pupal deformation, and pupal mortality.

Cattle feces containing selected concentrations of monensin (Rumensin®) that ranged from 3.125 to 100 ppm resulted in an LC50 and LC90 of 10.71 and 49.05 ppm, respectively, for the face fly, Musca autumnalis De Geer, and 24.71 and 59.12 ppm, respectively, for the horn fly, Haematobia irritans (L.). A dosage concentration response was seen with puparial weights of both species.

A methoprene nasal treatment of lambs at dosages of 0.1, 0.5, 0.75, 1, and 1.5 mg/lamb significantly reduced pupation and emergence of adult Oestrus ovis L. but not larval development. Emergence of adults was inhibited by 86.4 to 100% but not necessarily in the order of increased dosage.

Field comparisons of Dow ET-57 and malathion for determination of larvieidal efficiency against house flies and other types of Diptera under caged laying hens were made, using surface application of 1¼% solutions. Dow ET-57 gave an overall control of 78 to 99% at the end of the first and second week, respectively, while malathion gave a corresponding 0 to 67% control.

Coumaphos is recommended in 1964 USDA Handbook 120 as a 0.25% spray for lice control on beef cattle. The purpose of this experiment was to examine lower concentrations of coumaphos for possible control of lice, as the mentioned concentration might exceed the dosage needed for satisfactory lice control.