Elizabeth Ruth Miller

Variation in body size and flight performance in milkweed bugs (Oncopeltus).

In this paper we report observations on variation in flight performance and body size among tropical, temperate, and island milkweed bugs (Oncopeltus: Hemiptera: Lygaeidae). This is one of a series of papers on life history variation in Oncopeltus; photoperiodism is discussed in Dingle et al. (1980) and size dependent timing of metamorphosis in Blakley and Goodner (1978). Other papers are in preparation. The distribution of these bugs throughout much of the Western Hemisphere (Slater, 1964) allows comparison, both within and among species, of the selective forces acting on life histories. Various species occur in tropical and temperate regions and on islands throughout the Caribbean on milkweeds (Asclepiadaceae) and occasionally on plants of related families. One species, Oncopeltus fasciatus, is a long distance migrant to temperate North America (Dingle, 1968a et seq.), while the remainder are confined to the tropics and subtropics. General discussions of the ecology of these insects may be found in Blakley (1977), Dingle (1968a et seq.), Evans (1979), Ralph (1976, 1977), Root and Chaplin (1976), and Sauer and Feir (1973); a summary is included in Dingle et al. (1980) which also gives collecting sites for the populations discussed here. Migratory physiology is reviewed by Rankin (1978). All species discussed in this paper belong to the subgenus Erythrischius (Slater, 1964). We found that flight performance differed considerably among species and populations of Oncopeltus. Dispersal abilities of insects vary with habitat (Southwood, 1962; Dingle, 1972), and many species occurring in isolated habitats, including islands, are apterous or brachypterous (Carlquist, 1974; Vepsaldinen, 1978). There are, however, only a few studies (e.g., Rose, 1972) which demonstrate that relatively shorter (as opposed to functionless) wings actually lead to reduced flight and none, so far as we know, demonstrating reduced flight in cases where it would be expected, for example, on islands, but where there is no obvious alteration in wing structure. In this report we demonstrate that reduced flight can occur with no apparent changes in wing morphology. Body size has attracted considerable attention from evolutionary biologists. It is easy to measure, and it is associated with a number of other characteristics from life history statistics (Pianka, 1970; Stearns, 1976; Blueweiss et al., 1978) to an array of morphological and physiological traits (summarized by Pyke, 1978). Despite much effort by ecologists and others, however, the adaptive significance of body size is not well understood, and indeed there seems to be no general agreement on the most important selective factors (Pyke, 1978). Body size is also frequently influenced by proximate environmental conditions such as food availability, so that analysis is complex. Regardless of such phenotypic variability, the heritability of body size differences is more often assumed than demonstrated so that their adaptive nature falls short of proof. In this study we demonstrate heritable differences in body size between bugs of island 1 Present address: Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado 80309.

Respiratory symptoms and lung function abnormalities among machine operators in automobile production

This cross-sectional study was designed to assess differences in prevalence of respiratory symptoms and lung function between machine operators exposed to semisynthetic or soluble metal-working fluids (MWFs) and unexposed assemblers and to assess exposure-response relationships with MWF type, total aerosol, endotoxin, culturable bacteria and fungi. We evaluated 183 machine operators and 66 assemblers from one large automobile transmission plant using questionnaires, spirometry data, and cross-shift assessment of both lung function and respiratory symptoms. We found that airborne exposures to total aerosol, endotoxin, culturable bacteria and fungi were higher in machine operations than in the assembly area. There was a correlation between bulk and airborne culturable bacteria, but not between bulk and airborne culturable fungi. Machine operators had significantly more usual cough, usual phlegm, work-related chest tightness and post-shift symptoms of chest tightness, throat irritation, and cough compared with assemblers. We found exposure-response relationships between respiratory symptoms and total aerosol, as well as culturable fungi and bacteria. Associations with endotoxin were not strong or consistent, possibly because airborne levels were generally low. Cross-shift lung function decrements did not differ between machine operators and assemblers and there were no associations with MWF or specific exposures. The finding of respiratory symptoms at low levels of exposure in this study suggests the need to re-assess total aerosol thresholds. Associations between airborne fungal exposures and respiratory symptoms need further study to characterize sources of exposure other than MWF in machining operations.

Dermatitis among automobile production machine operators exposed to metal‐working fluids

This cross-sectional study was designed to assess differences in prevalence of contact dermatitis between machine operators exposed to metal-working fluids (MWFs) and unexposed assemblers, and to assess potential risk factors for contact dermatitis among these machine operators. In their work, machine operators were exposed to either semisynthetic or soluble oil MWFs. We evaluated 158 machine operators and 51 assemblers from one large automobile transmission plant using questionnaires, dermatologist examination of the skin, and dermal dosimetry to measure wetness and metal exposures. We found that machine operators had more combined (definite plus possible) dermatitis (27.2% vs. 13.7%, chi(2) = 3.9, p = 0.05, 1 df) compared with assemblers. Among machine operators, risk factors significantly associated with (combined) dermatitis were subjective assessment of wetness of the work, exposure to semisynthetic as opposed to soluble oil MWF, current cigarette smoking, and increasing worker age. These risk factors suggested preventive and control measures including control of wet work, surveillance program including early self-report of dermatitis, consideration of replacement of semisynthetic with soluble oil MWFs, and strictly limiting smoking among machine operators exposed to MWFs.

Injuries among construction workers in rural Iowa: emergency department surveillance

Surveillance of all emergency department admissions for nine rural hospitals identified visits for injuries by 189 employed patients with construction occupations out of a total of 1843 injury visits of all employed patients with known occupations. The injury rate for construction workers was 20.28 injuries per 100 workers per year-more than 2.5 times that of all other employed people. The work-related injury rate was 7.63 per 100 construction workers, more than four times that of all other employed people. The injuries of construction workers seen in the emergency department were primarily open wounds, fractures and dislocations, and contusions, injuries similar to those of other workers. The percentage of work-related burns was higher in construction workers than for other workers, particularly because of burns to roofers and laborers from tar or hot fluids and flash burns from welding.

Method to Electronically Collect Emergency Department Data

STUDY OBJECTIVE To describe the development and completeness of an electronic injury-surveillance system, the Rural Injury Surveillance System (RISS). METHODS The emergency departments of nine rural Iowa hospitals submitted information on all patients treated from May 1993 through June 1994. RESULTS The EDs submitted information on 23,594 patients with 32,445 different injury, disease, or follow-up visits. On the basis of comparison with the handwritten ED logbook, 90% of visits were also available in the RISS. Of the visits recorded in the RISS, 99% were also recorded in the logbook. The proportion of missing diagnostic codes decreased from a high of 22.6% in May 1993 to 8.1% in June 1994. The proportion of missing external cause codes was about 25% at the end of the study period. The proportion of missing industry and occupational codes was less than 5% at the end of the study period. CONCLUSION Our findings show that complete, computerized, ED-based injury surveillance in rural EDs is possible and should be developed further.

The utility of preliminary surveys to detect the cause of acute metalworking fluid hazards

This paper describes preliminary studies undertaken to optimize a later epidemiologic study, the aim of which was to identify a causative agent of adverse respiratory effects and dermatitis among production machinists. Two methods were used to rate coolant system hazards. The results of a voluntary plantwide questionnaire with an 18% participation rate showed that both dermatologic and respiratory symptoms were higher among machine operators than among maintenance or assembly workers, that symptoms were not more prevalent early in the week, and that dermatitis may be associated with smoking status; however, the questionnaire was not helpful in rating individual coolant system hazards. The hazard ratings provided by an in-plant expert panel were strongly associated with particular synthetic coolant containing an ethoxylated phenol; however, the resulting design for a later epidemiologic study could not be implemented due to changes in coolants used at the plant.

Nerium oleander as an alternative host plant for south Florida milkweed bugs, Oncopeltus fasciatus

Abstract. 1 Life history data were gathered for south Florida Oncopeltus fasciatus reared from eggs on Nerium oleander seeds and milkweed seeds in the laboratory. 2 Milkweed seeds were found to be a superior food source since O.fasciatus grew faster, laid more clutches, and has a higher total fecundity on milkweed seeds. 3 Fruiting N.oleander was found to be a better food source than nonfruiting milkweeds in a summer field study in south Florida since no nymphs survived to the adult stage on nonfruiting milkweeds but some did on N.oleander. 4 O.fasciatus adults and nymphs are abundant on N.oleander in the summer in south Florida when N.oleander is fruiting; no O.fasciatus nymphs are found in the summer on the milkweeds which are not fruiting. 5 O.fasciatus leave N.oleander in the autumn when milkweeds start to fruit and can then be found on fruiting milkweeds.

The effect of host plant phenology on reproduction of the milkweed bug, Oncopeltus fasciatus, in tropical Florida

SummaryA field study of the relationship between host plant phenology and the reproductive pattern of the large milkweed bug, Oncopeltus fasciatus, was conducted in south Florida. Since O. fasciatus need seeds of either milkweed or Nerium oleander plants to reproduce, reproduction takes place on only those host plants that are producing seed pods.Two of four major host plants, Asclepias incarnata and Sarcostemma clausa fruit seasonally, producing pods in early autumn and early winter, respectively. The third milkweed host, Asclepias curassavica, produces almost no pods midsummer (although it flowers abundantly) and few pods midwinter. Nerium oleander (Apocynaceae) produces some pods all year but is only used by O. fasciatus in the summer when milkweeds are not producing pods. Correspondingly, reproduction of O. fasciatus has been observed year round, but relatively few females reproduce in midwinter, coinciding with decreased pod production and low temperatures. This pattern is consistent with the hypothesis that a photoperiodic cue of short day lengths under conditions of cool temperatures may cause adult females to enter diapause and delay reproduction in the field.A comparison of plant phenologies and rainfall between 1976, a very dry year, and 1978, a year with normal rainfall, showed that extreme dryness disrupted the seasonal fruiting of the milkweeds and consequently the reproduction of O. fasciatus.