Stable flies sense and behaviorally respond to the polarization of light.

Insects use their polarization-sensitive photoreceptors in a variety of ecological contexts including host-foraging. Here, we investigated the effect of polarized light on host foraging by the blood-feeding stable fly, Stomoxys calcitrans, a pest of livestock. Electroretinogram recordings with chromatic adaptation demonstrated that the spectral sensitivity of stable flies resembles that of other calyptrate flies. Histological studies of the flies' compound eye revealed differences in microvillar arrangement of ommatidial types, assumed to be pale and yellow, with the yellow R7 and pale R8 photoreceptors having the greatest polarization sensitivity. In behavioural experiments, stable flies preferred to alight on horizontally polarized stimuli with a high degree of linear polarization. This preferential response disappeared when either ultraviolet (UV) or human-visible wavelengths were omitted from light stimuli. Removing specific wavelength bands further revealed that the combination of UV (330-400 nm) and blue (400-525 nm) wavelength bands was sufficient to enable polarized light discrimination by flies. These findings enhance our understanding of polarization vision and foraging behavior among hematophagous insects and should inform future trap designs.

The relationship between maternal pre-pregnancy body mass index and exclusive breastfeeding initiation: Findings from an Australian obstetric cohort.

BACKGROUND: To assess the type of infant nutrition at initiation of first feed in association with increasing maternal pre-pregnancy Body Mass Index in an Australian obstetric population. METHODS: A retrospective cohort study from 2008 to 2013 was undertaken. Body Mass Index was available for 12,347 women categorised into groups according to: underweight (≤18 kg/m2); normal weight (19-24 kg/m2); overweight (25-29 kg/m2); obese class I (30-34 kg/m2); obese class II (35-39/kg2) and obese class III (40+ kg/m2). Type and initiation of infant feeding is routinely recorded in the study hospital's birthing outcomes system. Six body mass index categories and mode of infant feeding were examined using logistic regression. Confounding factors that were controlled for included smoking status, parity, country of birth and maternal age. RESULTS: Within this cohort, 609 (4.93%) women were underweight, 6235 (50.50%) had a normal BMI, 3116 (25.24%) were overweight, 1314 (10.64%) were obese class I, 596 (4.83%) were obese class II and 477 (3.86%) were obese class III. In adjusted models', as BMI rose, women were significantly less likely to initiate exclusive breastfeeding and more likely to exclusively formula feed. Women with a BMI of 40+ kg/m2 had an AOR of 2.91(CI 1.94-4.25) for initiating exclusive formula at the time of their infant's first feed. CONCLUSIONS: Women who are overweight or obese are significantly less likely to initiate exclusive breastfeeding and more likely to give exclusive formula at the time of their newborn infants first feed. Effective breastfeeding interventions are required for these high-risk groups in the days leading up to and within the first hours after birth.