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The history is recounted of developing the sterile insect technique to eradicate the screwworm, Cochliomyia hominivorax (Coquerel), from the Caribbean island of Curacao, Florida and the southeastern U.S. Observations of screwworm biology and challenges faced in conducting these eradication projects are described by the author who worked on all aspects of the research and field operations. Eradication was first demonstrated on Curacao, essentially a 170 mi2 outdoor laboratory. The population dynamics of the wild screwworm was determined and overflooding ratios and dispersal patterns essential for population suppression were defined. Eradication was achieved with minimal resources by attacking the pest during the time of year when it is least abundant. In Florida, eradication was greatly facilitated by an unusually cold winter that reduce the range and density of the target population. Eradication could not be attained easily by only suppressing the reproduction of adult screwworms. The larval population also had to be reduced to increase the ratio of sterile to wild males. It was essential to control the immature stages by diligent inspection and treatment of animal wounds. Leadership of the cattle producers was critical not only for securing program resources from the clientele, state legislatures and U.S. Congress, but also for gaining the cooperation of virtually all livestock owners. Additionally, leadership was required to acquire adequate research, extension and public information resources. Lessons learned from this work were corroborated repeatedly as the screwworm eradication program moved into the Southwest, Mexico and the Central America.

Electric grid traps baited withHeliothis subflexa (Guenee),H. virescens (F.), orH. zea (Boddie) females captured conspecific males with few exceptions.Heliothis subflexa females reduced the attraction ofH. virescens andH. zea males when used as bait simultaneously with females of either of these two species. Backcrosses were made withH. virescens males and female hybrids from a cross betweenH. subflexa females andH. virescens males. The backcross (BC) females andH. virescens females attracted approximately equal numbers ofH. virescens males in field traps. BC males released in field cages were attracted toH. virescens females and to the synthetic pheromone ofH. virescens. When laboratory-reared maleH. virescens, BC males,H. subflexa males, and F1 hybrid males were exposed to the synthetic pheromone ofH. virescens in Plexiglas wind tunnels,H. virescens males and BC males responded to the pheromone, butH. subflexa and F1 hybrid males did not. The peak activity of bothH. subflexa andH. zea males occurred approx. 4 hr after sunset. MaleH. zea were active throughout most of the night; maleH. virescens were most active approx. 6 hr after sunset.

A pheromone released by courting male tobacco budworm moths, Heliothis virescens (F.), to repel other males of that species has been identified as (Z)‐9‐tetradecenal. The amount of this compound isolated from 3‐day‐old male abdomens was 1 mg/male.

In field trapping experiments, 16∶1 and 32∶1 blends of (Z)-9-tetradecen-1-ol formate (Z-9-TDF) and (Z)-9-tetradecenal (Z-9-TDAL) caught as manyHeliothis virescens (F.) as 3 virgin females and virelure, the synthetic pheromone of this species [a 16∶1 mixture of (Z)-11-hexadecenal (Z-11-HDAL) and (Z)-9-tetradecenal]. Z-9-TDF and (Z)-7-dodecen-1-ol formate (Z-7-DDF) are structurally similar to Z-11-HDAL and Z-9-TDAL, respectively. The sensory input elicited by Z-9-TDF appears to substitute for the sensory input of Z-1 1-HDAL. In contrast, Z-7-DDF had no significant effect on catches of maleH. virescens when used alone, in combination with either Z-11-HDAL or Z-9-TDF as a bait in traps, or as a disruptant of pheromone communication via permeation of the atmosphere. Furthermore, Z-9-TDF may be a more stable and economical attractant forH, virescens males than is Z-1 1-HDAL.

Blacklight traps were operated for 43 months at a density of 3 per square mile on an isolated tropical island, St. Croix, U. S. Virgin Islands, to determine the effect on populations of 25 insect species. Subsequently, the density of traps was reduced to 0.3 per square mile for 18 months, and changes in the collections were noted. The test species were: Agrius cingulatus (F.), Callionima ramsdeni (Clark), Eumorpha vitis (L.), Hyles lineata (F.), Manduca rustica harterti (Rothschild), Manduca sexta (L.), Xylophanes pluto (F.), X. tersa (L.), Heliothis virescens (F.), H. zea (Boddie), Ecpantheria icasia (Cramer), Gryllus assimilis (F.), Microcentrum triangulatum Brunner, Neoconocephalus triops (L.), Schistocerca pallens (Thunberg), Acrosternum marginatum (Palisot De Beauvois), Loxa pilipes Horvath, Nezara viridula (L.), Jadera rufofusca Barber, Bothynus cuniculus (F.), Phyllophaga microphylla Moser, P. portoricensis (Smyth), Calosoma alternans alternans (F.), Conoderus sp. and Lacon subcostatus (Candeze). Many species had decreased populations as measured by BL trap collections during the 43 months, and within a year after the trap density was reduced most had surges to population levels as high or higher than those recorded during masstrapping. Lepidopteran population indices were more affected than indices of other orders. Generally, most decreases and increases in populations appeared to be related to the trapping, but the numbers of some species that were removed by the traps were so low that any effect was indirect. Blacklight traps have a potential as a supplement for other control measures or possibly as a control themselves if the trap area is sufficiently large or sufficiently isolated.

Analyses of solvent rinses of the external surfaces of pheromone glands excised from calling female tobacco hornworm moths, Manduca sexta (L.), revealed the presence of the following compounds: (Z)-9-hexadecenal, (Z)-11-hexadecenal, (E)-11-hexadecenal, hexadecanal, (E,Z)-10,12-hexadecadienal, (E,E)-10,12-hexadecadienal, (E,E,Z)-10,12,14-hexadecatrienal, (E,E,E,)-10,12,14-hexadecatrienal, (Z)-11-octadecenal, (Z)-13-octadecenal, octadecanal, and (Z,Z)-11,13-octadecadienal. The two trienals were identified by mass and PMR spectral analyses and by ozonolyses, and their structures were confirmed by synthesis. In a wind tunnel male tobacco hornworm moths exhibit the same behaviors in response to a synthetic blend of all of the components, the gland rinse, or a calling female. Both (E,Z)-10,12-hexadecadienal and (E,E,Z)-10,12,14-hexadecatrienal are required to stimulate males to complete the characteristic behavioral sequence: anemotaxis, approaching and touching the pheromone source, and bending their abdomens in apparent copulatory attempts. The other components of the blend may play more subtle roles.

When female Heliothis virescens (F.) moths were given a choice between a typical flue-cured tobacco, NC 2326. and a primitive tobacco introduction. TI 1112, in screened oviposition cage tests, 74 to 91% of the eggs were laid on NC 2326. In no-choice tests, moths deposited over twice as many eggs on NC 2326 as on TI 1112 plants. The relative attractiveness of tobacco leaves, as measured by eggs oviposited per cm2 of leaf, decreased for both plant types with an increase in leaf number, as measured from the plant bud. Over 87% of the eggs were found on the upper five leaves of both plant types, and 75% (TI 1112) and 79% (NC 2326) of the eggs were laid on the lower surface of the leaves.

The nocturnal behavior of the tobacco budworm, Heliothis virescens (F.), cabbage looper, Trichoplusia ni (Hubner), tobacco hornworm, Manduca sexta (L.), and soybean looper, Pseudoplusia includens Walker, was observed in a 0.4-ha cage planted to cigar-wrapper tobacco for ca. 3 months. Ambient air and dew point temperatures, night brightness, wind speed, and relative humidity were recorded in an attempt to relate these meteorological parameters to moth behavior. The general pattern of moth activity indicates early evening and early morning peaks of feeding interspersed with oviposition. Mating generally followed a period of moth flight inactivity that occurred just after the early evening peaks in feeding and ovipositional activity. Females were observed “calling” for mates during the inactive flight period, and precopulatory behavior was observed and described. The cabbage looper and tobacco hornworm generally mated earlier in the evening than the soybean looper and tobacco budworm whose mating periods were quite similar and occurred primarily between 10 PM and 4 AM. Mating occurred on both dark and bright nights, but most mating took place during dark periods. However, the tobacco plants and cage cover created an abnormally dark condition within the cage during most of the experimental period. Also, most mating occurred at temperatures near 21.1 °C and a relative humidity above 90%, but these parameters were quite uniformly high throughout the experimental period. Similarly, the wind velocities experienced in the test did not appear to influence mating behavior.

Screw-worms, Callitroga hominivorax (Cqrl.), did not exist in the southeastern United States until about 20 years ago, and it is probable that, if the present infestation could be eradicated, the area might be kept free of infestation through inspection of livestock shipments originating in infested areas.

Screw-worms ( Cochliomyia hominivorax (Coquerel)) have shown variable response to the standard dose level of gamma rays from cobalt60 sources used in routine production of sterile flies for eradication of this insect. The primary influence was found to be availability of oxygen during irradiation. When pupae were irradiated in a carbon dioxide atmosphere, a dosage of of 11,100 roentgens (r) was required to sterilize the females, compared with only 5,500 r to 6,200 r required in oxygen and air (forced ventilation). Anoxia induced by consumption of oxygen by the pupae produced radiation-protection effects that were intensified by delay prior to irradiation and/ or increased rate of oxygen uptake as pupae advanced in age. In practical tests, a canister made of 1/8-inch mesh aluminum screen provided sufficient diffusion of air to standardize the dosage safely at 6,900 r, with up to 30 minutes’ delay prior to treatment for pupae 5 days of age or older. This dosage reduces by 50% that required under maximum conditions of anoxia encountered in production when a closed canister is used.

Artificial selection of adult screw-worms, Cochliomyia hominivorax (Coquerel), for resistance to starvation carried through 28 generations resulted in improved survival potential. Initial starvation of 56 hr caused 85% ♂ and 92% ♀ mortality, but in F12–11 mortality was only 3.6–4.4% for males and 6.1–12.0% for females. Starvation of 72 hr in F12 killed 53.5% ♂ and 72.4% ♀. After 96-hr starvation in F16, 72-hr mortality in F20–28 was no greater than for fed flies. At the 50% mortality level survival was increased from 48 to 96+ hr in 28 generations. Relaxation of pressure in F1S resulted in no loss of resistance 10 generations later. Adults utilized posteclosion food reserves rapidly in spite of food availability, indicating need for prompt release after eclosion in programs utilizing irradiated males for eradication. Females were more susceptible to starvation than males and egg development was inhibited. Selected flies were 8–10% heavier than unselected and fat body content of selected males was almost twice that of unselected. Sexual vigor of selected males was reduced in F13 and later generations, but vigor of a substrain removed from selection in F13 showed improvement 7 and 9 generations later, indicating need for a compromise between maximum survival and acceptable sexual vigor. During 96-hr starvation males mated more readily than females.

Samples of the adult sterile oriental fruit fly, Dacus dorsalis Hendel, and the melon fly, D. cucurbitae Co-quillett, emerging in drop boxes before aerial releases were made over Rota Island in the Marianas to eradicate these species, showed that the confinement significantly decreased survival and increased mutilation. The percentage survival of 3-week-old oriental fruit flies emerging in the drop boxes was 43.7% less than that of similar flies emerging in normal cubical holding cages for adults; that of melon flies was 35.5% less. Mutilation (wing or body damage) of both species was proportional to the density of the flies in the boxes, but the melon fly was the more susceptible to damage. Sugar + water (2:1 ratio) or honey + sugar + water (1: 1:1 ratio) made available during emergence caused significantly better survival of the melon fly than honey + water (2:1 ratio).

The effect of accelerated female mortality owing to harassment by male screw-worms, Cochliomyia hominivorax (Coquerel), was utilized in a test for sexual aggressiveness (SAG test) of males based on female mortality resulting from males present at a 3:1 ratio. Strains mating well in the SAG test also mated well in competitive tests, but inferior males mated effectively in the absence of competition. Data from earlier tests in which flies were held in a 1:1 male-female ratio after irradiation were re-examined. Apparently because of relief from harassment by males, female mortality was reduced and treated females lived as long as untreated. Fallacy of longevity data as an index of sexual vigor was demonstrated in SAG tests in which some inactive males lived as long as sexually aggressive males. The SAG test showed greatly reduced male activity as the radiation dose increased from 3 to 12 kr for 5-day-old pupae; however, for 6- and 7-day pupae only minor reductions occurred. Both Florida (Fla) and yellow eye (y) mutant males effectively reduced y female longevity, but y males were ineffective against Fla females. Males from both strains mated twice as many y as Fla females when an abundance of females of both strains was present.

Timing of emergence of adult Cochliomyia hominivorax (Coquerel) from puparia was found to be entrained within the larval stage of each generation if the larvae were reared with a regimen of 12 hours light:12 hours dark. However, the peak of emergence within the circadian cycle could be shifted from early morning to late afternoon by rearing a single generation with a regimen of 4 hours light:20 hours dark. The entrained circadian rhythm was unaffected by photo periodic regimens in the pupal stage. The periodicity of adult emergence appears to be induced early in larval development. These findings are applicable to a sterile-male-release program.

Blacklight traps at a density of 3/mile2 were operated for 43 months (1966–69) on St. Croix, U. S. Virgin Islands, an isolated tropical island. Insects were collected regularly from ⅓ of the traps to obtain an index of the size of the population of 17 insect species. The species studied were: Acrosternum marginatum (Beauvais), Bothynus cuniculus (F.), Conoderus sp., Ecpantheria icasia (Cramer), Gryllus assimilis (F.), Heliothis virescens (F.), H. zea (Boddie), Jadera rufofusca Barber, Lacon subcostatus (Candeze), Loxa flavicollis (Drury), Microcentrum triangulatum Brunner, Neoconocephalus triops (L.), Nezara virdula L., Phyllophaga microphylla Moser, P. portoricensis (Smyth), and Schistocerca pallens (Thunberg). The populations of most species declined in 1967 and 1968 but increased in 1969. The decreases may have been related to the trapping and the increases to an abnormally high rainfall in 1969.

Hourly sampling catches of Manduca sexta (L.) in electrocutor grid traps baited with a blacklight lamp, virgin females, or both attractants, indicated that these moths are active all night in the Gainesville, Florida, area. Traps baited with females captured only males; traps baited with blacklight and blacklight + females caught both sexes. Many more males than females were captured at all hours of the night. Peak catches of males occurred between 2 and 4 AM EDT in each of the 3 treatments. Most females were captured between sunset and midnight.

Approximately 500 sterile male screw-worm flies ( Callitroga hominivorax (Cqrl.)) were released weekly per square mile over a 2,000-square-mile area in Florida. The insects had been irradiated as pupae, within 2 days of adult emergence, with 6,200 to 8,300 r gamma rays from cobalt-60. They were packaged at the rate of 880 (later 550) pupae per release carton. Flies were distributed daily in 6-mile swaths by small aircraft. Shifting of flight lanes resulted in the area being covered in 1-mile swaths weekly. Egg-mass collections in the treated area declined from a weekly average of 41 per station during the first 2 months to 11 in the 12th week. Check stations indicated a continuing high population north of the treated area but a decline on the west and south. However, at the end of 3 months 70% of the egg masses were sterile.

Cylindrical electric grid traps baited with synthetic pheromone of the cabbage looper, Trichoplusia ni (Hubner), caught 6–7 times more males than a similarly baited can trap developed specifically for this insect. Also, grid traps baited with virgin female tobacco hornworms, Manduca sexta (L.), were 2–9 times more effective in trapping males than a screenwire pheromone trap designed for this purpose. Moreover, when both attractants were used together on the same grid trap both cabbage loopers and hornworms were captured, indicating that it can be used with at least 2 different pheromones simultaneously.

When blacklight traps were operated at a density of 3/mile2 for 43 months on St. Croix, U. S. Virgin Islands, the collections of sphingid moths were found to be associated with the seasonal pattern of rainfall. The 12-month collection of Hyles lineata (F.) was 17.5% of the 1st 12 months collection after 43 months. The collcction of Callionima ramsdeni (Clark) had dropped 50% after 33 months of trapping but increased to 64% of the 1st 12 months after 43 months. The collection of Agrius cingulatus (F.) was 32% that of the 1st year after 36 months but increased to 81% after 43 months. The collection of Manduca rustica harterti (Rothschild) was 14% that of the base year after 39 months but increased to 21% after 43 months. The collection of Eumorpha vitis (L.) was 15% that of the base year after 39 months but increased to 19% after 43 months. The collection of Xylophanes pluto (F.) was 36% that of the initial year after 36 months but increased to 70% after 43 months. The collection of Xylophanes tersa (L.) was 59% that of the base year after 37 months but increased to 80% after 43 months. The increased collections the last year of trapping were attributed to the absence of a dry season that year. If the collection trends prior to that unusual rainfall pattern had continued, several species would have been eradicated by an additional year of trapping pressure.

Populations of Manduca sexta (L.) were reduced by 86% on St. Croix, U. S. Virgin Islands, when blacklight traps at a density of 3/mile2 were operated for 43 months; during the last 22 months, most traps were baited with virgin female tobacco hornworm moths. The collections indicated that hornworms were present throughout the year and that 2 periods of high population occurred each year, both associated with rainy seasons. When the collections of females from 9 traps operated for a year before the mass trapping began were used as a base for comparison, the yearly reductions in the mean collections for 12 months ending in December were: 60% from 1966 to 1967; 51% from 1967 to 1968; and 24% from 1968 to 1969. Annual operation of blacklight traps during the periods of maximum activity of the tobacco hornworm moth would reduce populations of the insect in similar situations and probably also in continental land masses.

During 1953 regional similarities in activity patterns of the screw-worm, Cochliomyia hominivorax (Coquerel), were used to group infestations in northern Mexico into 5 provisional zones. In the first zone, widespread infestations were noted as early as April, with population peaks in July and October. In the second zone, sustained screw worm activity was limited to periods following rains. Patterns of screw-worm activity in the third zone were similar to those in the first, but the seasonal weather cycles were dissimilar. The fourth and fifth zones showed a single peak of screw-worm activity in the late summer.

In small field plots, (Z)-9-tetradecen-1-o1 formate (Z-9-tdf) alone was highly disruptive of pheromonal communication between male and female corn earworms, Heliothis zea (Boddie), and male and female tobacco budworms, H. virescens (F.). Z-9-tdf was not disruptive of pheromonal communication between males and females of several species of looper moths including Trichoplusia ni (Hubner), Pseudoplusia includens (Walker), and T. oxygramma (Geyer). In contrast, (Z)-7-dodecen-1-o1 acetate (Z-7-dda) was an effective disruptant of pheromonal communication of the looper moths, but did not affect male H. zea or H. virescens . However, when Z-9-tdf was mixed with Z-7-dda in equal quantities and evaporated into the air simultaneously in the same plot, the pheromonal communication of all 5 species was disrupted. These compounds are stable, relatively inexpensive, and commercially available. They appear to offer promise for control of mating in these important species, and they have potential as multichemical disruptants in broad spectrum control via atmospheric permeation.

A close correlation existed between the reductions in capture of males by ♀-baited traps and the reductions in mating by females (relative to controls) of Heliothis zea (Boddie) and H. virescens (F.) in small field plots treated with ( Z )-9-tetradecen-1-ol formate. Similar correlated reductions in trap capture and mating by Spodoptera frugiperda (J. E. Smith) were recorded in plots treated with ( Z,E )-9,12-tetradecadien-1-ol acetate. When these 2 chemicals were evaporated simultaneously from separate dispensers in the same plot, mating of H. zea and S. frugiperda females was reduced by 87 and 92%, respectively. In small field tests, ( Z )-l1-hexadecenal, a component of the H. virescens pheromone, reduced the mating of H. zea females by 85%. ( Z )-9-tetradecenal, another component of the H. virescens pheromone, was ineffective against H. zea but reduced the mating of H. virescens females by 95%.

Two tractor-mounted devices collected about 83,500 stilt bugs, Jalysus spinosus (Say) from ca. 25 ha of tobacco during the fall of 1972 and 1973. Due to rapid growth of microorganisms collected with the bugs, only 1% of the stilt bugs stored at 12.8°C survived 83 days. However, 19% of the stilt bugs stored in outside cages at ambient temperature survived 160 days.

In the search for improved techniques for the mass production of screw-worm flies ( Cochliomyia hominivorax (Coquerel)) for irradiation and release in an eradication program, one of the more elusive problems has been mortality of pupae caused by desiccation. It was found that the critical period of susceptibility to desiccation exists during the larval and prepupal stages (0 to 48 hours after larvae leave the rearing medium), and that losses sustained in the past can be attributed primarily to delay in providing protection. Screw-worms exposed as full-grown larvae to 90° F. and 40% R.H. for 48 hours suffered a weight loss of 53.5% and only 19.6% survived, compared with a weight loss of only 24% and 94% survival for controls protected with sand cover and room conditions of 85% R.H. A 24-hour exposure after pupation resulted in 31.9% weight loss and 61.4% survival in contrast to weight loss of only 16.1% and 93.7% survival for the controls. Screw-worms protected for 24 hours after pupation suffered minor losses when transferred to conditions of low humidity. Clarification of this critical period of susceptibility to desiccation should greatly improve handling of screw-worms after larval crawl-off and establish a firm basis for avoiding the serious loss from pupal mortality that occurred during the screw-worm eradication program in the Southeast.

In 1954, before the sterile insect technique was used to eradicate screwworms Cochliomyia hominivorax (Coquerel) from Florida and the southeastern United States, the concept was tested on the 440-km2 island of Curacao. The island had long had a screwworm problem, and B. A. Bitter, then with the Veterinary Service, requested advice from the U. S. Department of Agriculture on how to deal with it. Since the Department needed a small isolated location to test the then unproved sterile insect technique and island authorities agreed to cooperate, the experiment was begun on 17 March 1954 (Baumhover, Graham, Bitter, Hopkins, New, Dudley & Bushland, 1955, J. Econ. Entomol. 48 : 462–66), The effort was quickly successful. The last screwworm egg mass was collected on 11 November 1954, and the first unequivocal eradication of an established insect with the sterile male technique was accomplished.

In an insect, the tobacco hornworm Manduca sexta, the cerebral neuropeptide prothoracicotropic hormone (PTTH), the primary effector of postembryonic development, exists as two molecular forms. These two PTTH's elicit characteristic in vitro dose responses of activation of prothoracic glands from different developmental stages, an indication that during development the glands change in their sensitivity to the neurohormones. Both PTTH's are active in a specific in situ bioassay. Since they may be released in situ at stage-specific times to evoke distinctly different developmental responses, the PTTH neuroendocrine axis appears to be an effective system for determining the functions of molecular forms of a neurohormone in the regulation of growth and development.

The tritium-labeled synthetic ecdysone analog Delta(7)-5beta-cholestene-2beta,-3beta,14alpha-triol-6-one terminated diapause when injected into diapausing tobacco hornworm pupae and was converted into tritium-labeled alpha-ecdysone and tritium-labeled 20-hydroxyecdysone. About half of the crystalline alpha-ecdysone and 20-hydroxyecdysone isolated from the tobacco hornworms 7(1/2) to 8(1/2) days after injection was derived from endogenous steroid precursors and half from the transformation of the synthetic ecdysone analog.

Captures of male Trichoplusia ni (Hubner) in cylindrical electric-grid traps baited with synthetic sex pheromone, declined with increasing elevation from 2 to 10 ft above ground. Collections of Manduca sexta (L.) in similar traps baited with virgin females were not affected significantly by the same range of elevations. Collections of T. ni with 12-, 18-, and 24-in.-diam grids, but with the same electrode spacing (½ in.), did not differ significantly; however, ¼-in. electrode spacing was 38% more effective than ½-in. spacing on the 12-in.-diam grids. The largest number of M. sexta moths was caught by the smallest-diameter grid, and the size of collections decreased as the diameter increased.

Collections of male tobacco horn worms, Manduca sexta (L.), in blacklight (BL) traps can be increased 10 or more times by baiting the traps with virgin female moths (Hoffman et al. 1966, Cantelo and Smith 1971). However. the rearing of these females is expensive and time consuming, and a synthetic female pheromone is not available. Therefore, we hoped to find a substitute material that could be used to increase collections. Isoamyl salicylate was chosen for evaluation because when it was used to bait relatively inefficient screen traps in Tennessee, it caught as many as 925 tobacco hornworms in a season. Also, 16 other species of sphingids were caught, but only Byles lineata (F.) and Xylophanes tersa (L.) were caught “in numbers” (Morgan and Lyon 1928). Moreover, at Oxford, N. C., collections in 12 similar-type traps (Stahl 1954) baited with isoamyl salicylate plus simulated jimson weed flowers averaged 112 M. sexta and 155 tomato hornworms, M. quinquemaculata (Haworth), each year from 1942 through 1953 with peak yearly collections of 414 M. sexta and 218 M. quinquemaculata . (However, in 1949, unbaited BL traps collected 15 × as many hornworm moths (both species) and in 1952–53 7–9× as many as the baited screen traps.)

The maximum tobacco budworm, Heliothis virescens (F.), population on St. Croix occurs during October and November, while the low is during June, July and August. Pigeon pea and Bastardia serve as the principle host plants throughout the year. Population estimates show the species at a sufficiently low level to make St. Croix an excellent location for suppression or eradication studies.

Screwworms (Diptera, Calliphoridae,Cochliomyia hominivorax[Coquerell] are important obligate parasites of various terrestrial mammals, including man. Distribution is restricted during winter months to tropical and subtropical areas of North and South America; but during other periods, the screwworm fly may disperse 500 miles or more from its normal overwintering area. Life Cycle.— When held at 80 F (27 C), the adult flies mate at 2 to 3 days of age, and at 7 days of age, females oviposit shingle-like masses of 200 to 500 eggs. After an incubation period of 16 hours, larvae emerge and immediately start feeding in compact pockets, consuming primarily live flesh and wound fluids. In four to nine days after hatching, the larvae attain a body weight of 70 to 120 mg, drop from the wound, and burrow into the soil to pupate; adults emerge from the soil within eight days. Economic Importance.— Although the screwworm