Insect pests and their role as biocontrol agents on populations of Impatiens glandulifera in Bulgaria – a case study

Based on data from available scientific publications, a review of the insects, trophically related to Impatiens glandulifera in its European invasion zone has been made. As a result, nine insect species (Pristerognatha fuligana, Deilephila elpenor, Xanthorhoe biriviata, Chrysolina herbacea, Siobla sturmi, Impatientinum asiaticum, Aphis fabae, Aphis nasturtii, Phytoliriomyza melampyga) were found on the invasive plant. Of the identified insects, seven species (D. elpenor, X. biriviata, A. fabae, A. nasturtii, C. herbacea, P. fuligana, P. melampyga) are widespread in the country, of which only two – C. herbacea and  P. fuligana are associated with I. glandulifera. The remaining two (I. asiaticum and S. sturmi) are not pre-sented in the Bulgarian entomofauna. Тhe potential role of these insects as agents of biological control of populations of I. glandulifera in Bulgaria has been assessed.

Higher-order neural processing tunes motion neurons to visual ecology in three species of hawkmoths

To sample information optimally, sensory systems must adapt to the ecological demands of each animal species. These adaptations can occur peripherally, in the anatomical structures of sensory organs and their receptors; and centrally, as higher-order neural processing in the brain. While a rich body of investigations has focused on peripheral adaptations, our understanding is sparse when it comes to central mechanisms. We quantified how peripheral adaptations in the eyes, and central adaptations in the wide-field motion vision system, set the trade-off between resolution and sensitivity in three species of hawkmoths active at very different light levels: nocturnal Deilephila elpenor, crepuscular Manduca sexta , and diurnal Macroglossum stellatarum. Using optical measurements and physiological recordings from the photoreceptors and wide-field motion neurons in the lobula complex, we demonstrate that all three species use spatial and temporal summation to improve visual performance in dim light. The diurnal Macroglossum relies least on summation, but can only see at brighter intensities. Manduca, with large sensitive eyes, relies less on neural summation than the smaller eyed Deilephila , but both species attain similar visual performance at nocturnal light levels. Our results reveal how the visual systems of these three hawkmoth species are intimately matched to their visual ecologies.

Wide-field motion tuning in nocturnal hawkmoths

Nocturnal hawkmoths are known for impressive visually guided behaviours in dim light, such as hovering while feeding from nectar-bearing flowers. This requires tight visual feedback to estimate and counter relative motion. Discrimination of low velocities, as required for stable hovering flight, is fundamentally limited by spatial resolution, yet in the evolution of eyes for nocturnal vision, maintenance of high spatial acuity compromises absolute sensitivity. To investigate these trade-offs, we compared responses of wide-field motion-sensitive neurons in three species of hawkmoth: Manduca sexta (a crepuscular hoverer), Deilephila elpenor (a fully nocturnal hoverer) and Acherontia atropos (a fully nocturnal hawkmoth that does not hover as it feeds uniquely from honey in bees' nests). We show that despite smaller eyes, the motion pathway of D. elpenor is tuned to higher spatial frequencies and lower temporal frequencies than A. atropos , consistent with D. elpenor 's need to detect low velocities for hovering. Acherontia atropos , however, presumably evolved low-light sensitivity without sacrificing temporal acuity. Manduca sexta , active at higher light levels, is tuned to the highest spatial frequencies of the three and temporal frequencies comparable with A. atropos . This yields similar tuning to low velocities as in D. elpenor , but with the advantage of shorter neural delays in processing motion.

Reversed Light Reaction of the Screening Pigment in a Compound Eye Induced by Noradrenaline

Migration of the screening pigment in the compound eye of the sphingid moth Deilephila elpenor is altered by noradrenaline, as shown by microreflectometric measurements on eyes of intact moths and by transmission microscopy on preparations consisting of the screening pigment cells and dioptric structures. Local application of noradrenaline inverts the reaction of the pigment to light stimulation; light causes a contraction of the pigment instead of the normal dispersion. It is suggested that catecholamines are involved in the normal regulation of pigment migration.