Pollen feeding by adults of the hoverflyMelanostoma fasciatum(Diptera: Syrphidae)

Abstract

Pollen feeding by adult hoverflies of Melanostoma fasciatum, collected from organic paddocks at Flock House, Bulls, North Island, New Zealand, were studied by dissection. Up to six different pollen types were found in one hoverfly. On average, they fed only on 2.71 pollen species. 71% of gravid females but only 13% of males reached the maximum score (scale 0-5) for pollen content in the gut. Very few hoverflies had no pollen. Of the 15 identified pollen groups, plantain, phacelia, coriander, and graminaceous pollen were consumed in large quantities by gravid females. Differences in feeding spectra between sexes probably reflected the need for energy in males and for the protein required for egg maturation in females. Earlier views of strict preference for anemophilous pollen by M. fasciatum cannot be upheld.

The phenology and pollen feeding of three hover fly (Diptera: Syrphidae) species in Canterbury, New Zealand

“…For all species combined, gut fullness was higher in gravid females than in non-gravid females and males, and was higher in non-gravid females compared with males. This is consistent with the results of Hickman et al (1995), and supports the idea that females need pollen during summer/autumn to mature their eggs, whereas males need nectar to provide energy for mate seeking. Immature females had less pollen than did gravid females, perhaps because newly emerged females may take nectar for energy for mate seeking instead of consuming pollen Fig.…”

“…Gut fullness and the number of eggs in M. novaezelandiae and M. fasciatum were at their lowest from June to September, 1995, as was reported for M. fasciatum by Hickman et al (1995). In contrast, in E. tenax they were at their highest over the same period, with a peak of 108 eggs and a 5.5 gut-fullness index in August 1995 (Fig.…”

“…Gut fullness was estimated on a semi-quantitative scale by classifying pollen number as accurately as possible, without detailed counting at the higher pollen categories, into one of seven frequency classes (0 = no pollen grains, 1 = 1-10 grains, 2 = 11-100 grains, 3 = 101-1000 grains, 4 = 1001-3000 grains, 5 = 3001-5000 grains, 6 >5000 grains). Hickman et al (1995) working only on M. fasciatum, also dissected this species for pollen type and abundance. The pollen classes used in the present work did not exactly match those used by Hickman et al (1995) because the large pollen volumes contained in the E. tenax guts necessitated modified pollen-number classes.…”

“…Hickman et al (1995) working only on M. fasciatum, also dissected this species for pollen type and abundance. The pollen classes used in the present work did not exactly match those used by Hickman et al (1995) because the large pollen volumes contained in the E. tenax guts necessitated modified pollen-number classes.…”

“…reported that M. fasciatum and M. novaezelandiae produced a second generation in late summer in Canterbury, and that Taraxacum-type was the most frequently occurring pollen in the guts of both species. Hickman et al (1995) found that plantain (Plantago sp. ), Phacelia, coriander (Coriandrum sativum (L.)) and Gramineae (Poaceae) pollen was consumed in large quantities by gravid M. fasciatum females, and that there were differences in pollen feeding between the sexes.…”