[Syrphidae] tentorial pits

[Sergey Kuznetzov]

Dear Pierre-Nicolas,

More about  "the tentorial pits" you can find in the excellent  work -
"Manual of Nearctic Diptera", Vol.  1, 1981, p. 12  :

McAlpine, J.F. Morphology and terminology -- adults. In: Manual of Nearctic
Diptera, Ottawa:1981: 9-63.

P.12:  --  "The parts of the head are defined principally by the reference
to the occipital foramen (through which pass the nerve cords, esophagus,
aorta, and salivary ducts), the ocelli (sing. ocellus), the insertions of
the antennae, the margins of the eyes, the subcranial cavity (oral cavity),
and the anterior tentorial pits. The inner skeleton is formed  by the
tentorium (Fig. 5). Basically the tentorium consists of paired  anterior,
dorsal, and posterior tentorial arms. The anterior tentorial arms arise from
the anterior tentorial pits and the posterior arms arise from the posterior
tentorial pits. The dorsal tentorial arm is believed to be an outgrowth of
the anterior arm (Matsuda 1965), which it  joins near thejunction of the
anterior and posterior arms ...

The anterior tentorial pits are sometimes poorly developed or absent,
particularly in the Muscomorpha,(cyclorrhaphous Brachycera); they are very
large in some Nematocera, e.g. Culicidae, Chaoboridae  and Chironomidae, and
they are also easily seen in some Tabanomorph, for example in the Tabanidae.
The posterior tentorial pits, at ventral ends of the postoccipital suture,
are usually less evident".

With best wishes
Sergey Kuznetzov

Dr Sergey Yu. Kuznetzov
Zoological Institute
Russian Academy of Sciences
Universitetskaya embankment, 1
199034 St.Petersburg
Russia

e-mail: SergeyKuznetzov@mail.ru
WWW: http://www.dipterologic.sp.ru