Roy J. Barker

Sensitivity of Visual Receptors of Carotenoid-Depleted Flies: A Vitamin A Deficiency in an Invertebrate

House flies (Musca domestica) raised under sterile conditions on a diet lacking carotenoids and retinol (vitamin A) have visual receptor sensitivities —as assessed electroretinographically—which average more than 2 log units below normal, both in the near ultraviolet (340 m�) and visible (500 m�) regions of the spectrum. Loss of sensitivity can be prevented by the addition of β-carotene to the larval food. Flies reared for several generations on a carotenoid-free diet, but under conditions where the adults are not kept sterile, do not show a further loss of sensitivity. It is suggested that carotenoid stored in the egg prevents complete blindness in the first generation, and that microorganisms can supply small amounts of carotenoid and thereby prevent complete blindness in the second and successive generations.

Photoflashes: A Potential New Tool for Control of Insect Populations

Imported cabbageworms, Pieris rapae (L.), were reared in cans exposed to light from fluorescent lamps for 10 hours daily. When larvae were exposed to daily electronic photoflashes scheduled 3 to 4 hours after the fluorescent lamp was turned off, pupae failed to diapause. Effective wavelengths are lower than those controlling photoperiodism in plants. The effective energies are about 1 joule per square centimeter.

Pesticides and honey bees: nectar and pollen contamination in alfalfa treated with dimethoate.

Medicago sativa L. (Leguminosae) sprayed withO,O-dimethylS-(N-methylcarbamoylmethyl) phosphorodithioate (dimethoate) had only 0.5 ppm of dimethoate in pollen one day later, but 3 ppm in nectar one week later, and 1 ppm in nectar two weeks later. As little as 1 ppm added to syrup fed to caged workers ofApis mellifera L. (Apidae) inhibited cholinesterase and reduced survival. Bees given a choice between treated and untreated syrups showed no preference; this suggests that the levels of dimethoate found in nectar are toxic and not repellent.

Effects of dimethoate on honey bee foraging

Abstract Collection by honey bees of sucrose solutions treated with dimethoate continued uninterrupted until 2.9–3.9 μg/bee had been accumulated. This self-limiting dose was 20–25 times the oral LD50 for honey bees. Therefore a mean of 45 collection trips involving 1 ppm dimethoate or 11 trips involving 5 ppm was possible before foraging ceased. Losses in pollinator effectiveness and adult and larval mortality are likely to result from dimethoate contamination of nectar.

Free amino acids in thoraces of flown honey bees, Apis mellifera L. (Hymenoptera: Apidae)

Abstract 1. 1. The free amino acids were compared in the thoraces of flown and unflown honey bees, Apis mellifera L. Both workers and drones were tested. 2. 2. The amino acids showed little change with flight detectable by thin-layer chromatography on silica gel. By spectrophotometric analysis, a slight depletion in proline content with flight was observed. 3. 3. Evidently, proline is a minor source of flight energy in bees fed sucrose.

LIGHT‐DARK CYCLES AND DIAPAUSE INDUCTION IN PIERIS RAPAE (L.)

Diapause incidence was measured at 17°–20° in cycles of 12, 16, 20, 24, 28, 32, and 36 hours in which light comprised 0, 15, 25, 35, 45, 55, 65, 75, 85, and 100% of each cycle. Almost no diapause occurred when light was on for more than 55% of any cycle, and few insects diapaused on cycles of 12. 16, and 36 hours.

Infra-red absorption spectrum of the cuticular surface of drone honey bee wings as revealed by attenuated total reflectance☆

Abstract The infra-red absorption reflected through the shallow surface of wings of drone Apis mellifera did not show the ester groups expected of waxes. The functional groups that would accompany more than 5 per cent of other lipids were also absent. The observed reflection spectrum resembled that of pleated-sheet polyamides. This suggests that the surface of drone wings is comprised of a protein similar to silk, wool, hair, or human skin.

The Constancy of Cholinesterase Activity in Adult Honeybees

SummaryAlthough published data show the Cholinesterase level in adult worker honeybees found in hives to be more than double that in foraging honeybees, no significant change with age or activity was found when bees from indoor cages or free-flying outdoor colonies were assayed. It is concluded that when Cholinesterase levels are only half normal, poisoning of the bees should be suspected.

Pesticides and Honey Bees: The Danger of Microencapsulated Formulations

Abstract Microcapsules designed to improve the safety and persistence of pesticides are about the same size as pollen. Foraging bees collect pollen contaminated with such microcapsules and pack both together into hive combs. Sustained release formulations remain toxic in food stores of the colony. This combination of accumulation and persistence produces prolonged toxicity for bee colonies.

Factors influencing phototaxis of houseflies.

Abstract When houseflies, Musca domestica , were given a choice of crawling to dark or to radiation of varied wavelength and intensity, flies reared on a fermenting plant medium (CSMA) had a photonegative response to 525 to 575 nm radiation; flies reared on semidefined diet ( Monroe , 1962) had a photopositive response to this region. The photonegative response could be partly counteracted by adding cholesteral to the CSMA medium. The intermediate response to a mixture of the two diets suggested that the substances causing the difference are competitive. Females were more photopositive than males; older flies were more photopositive than newly emerged flies. The responses of larvae varied with age and differed from the responses of adults. Removal of wings did not alter the response of adults.