The ultrastructure and function of the silk-producing basitarsus in the Hilarini (Diptera: Empididae)

The tribe Hilarini (Diptera: Empididae), commonly known as dance flies, can be recognised by their swollen silk-producing prothoracic basitarsus, a male secondary sexual characteristic. The ultrastructure and function of the silk-producing basitarsus from one undescribed morphospecies of Hilarini, ‘...

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Bibliographic Details
Published in:Arthropod structure & development 2003-10, Vol.32 (2), p.157-165
Main Authors: Young, James H, Merritt, David J
Format: Article
Language:English
Subjects:
basitarsal glands
cells
Dance fly
Diptera
Empididae
Empidinae
exocrine glands
Glands
Hilarini
insect morphology
legs
males
mating behavior
Mating behaviour
Nuptial gift
nuptial gifts
secretion
Sensilla
silk
ultrastructure
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Summary:The tribe Hilarini (Diptera: Empididae), commonly known as dance flies, can be recognised by their swollen silk-producing prothoracic basitarsus, a male secondary sexual characteristic. The ultrastructure and function of the silk-producing basitarsus from one undescribed morphospecies of Hilarini, ‘ Hilarempis 20’, is presented. Male H. 20 collect small parcels of diatomaceous algae from the surface of freshwater creeks that they bind with silk produced by the gland in the basitarsus. The gift is then presented to females in a nearby swarm, composed predominately of females. The basitarsus houses approximately 12 pairs of class III dermal glandular units that congregate on the ventral side of the cavity. Each gland cell has a large extracellular lumen where secretion accumulates. The lumen drains to the outside via a conducting canal encompassed by a canal cell and a duct extending through the shaft of a specialised secretory spine. The secretory spines lie in pairs in a ventral groove that runs the length of the basitarsus. A comparison of the basitarsal secretory spines with sensilla on the basitarsi of non gland-bearing legs of males, and with non gland-bearing prothoracic basitarsi of females, suggests that the glandular units are derived from contact chemosensory sensilla.
ISSN:1467-8039
1873-5495
DOI:10.1016/S1467-8039(03)00006-9