Geoscience Reference
In-Depth Information
Other arthropods
Spiders are familiar to everyone, and the
kinds of spiders which were living around
Lake Florissant would, like the insects,
have been recognizable as similar to
living forms. Spiders are divided into
three groups: the most primitive
Mesothelae, known as fossils from
the Pennsylvanian (e.g. Mazon Creek,
Chapter 7) and the present day where
they are restricted to south-east Asia;
the Mygalomorphae (tarantula, bird-
eating, funnel-web, and trapdoor
spiders); and the so-called true spiders,
Araneomorphae. A single tarantula
(Theraphosidae) has been described
from Florissant: Eodiplurina cockerelli ,
by Alexander Petrunkevitch (1922), who
restudied the original specimens
described by Scudder (1890) as well as
some new ones. All the other Florissant
spiders are araneomorphs, and all
belong in modern families, some even in
modern genera. Segestriids, represented
by two species, build silken tubes in
crevices in bark and between stones.
Gnaphosids are ground-living hunters;
five species have been described from
Florissant. Clubionids (sac spiders) build
silken cells in which they stay during the
day, coming out at night to hunt;
Petrunkevitch (1922) recorded seven
species. A single species of day-hunting
wolf spider (Lycosidae) was described by
Petrunkevitch (1922), but he also
erected a new fossil family, Parattidae,
based on four species belonging
to Scudder's genus Parattus , which
was diagnosed on its unusual eye
arrangement. However, restudy of the
fossil has shown that the odd
eyes result from the way these spiders
have been compressed; they are really
lycosids. Three species of crab spiders
(Thomisidae) have been recorded.
These sit-and-wait predators can often
be found on flowers, mimicking the
color of the bloom, waiting for an
unsuspecting insect. The remaining
three families of spiders recorded at
Florissant weave webs to capture their
The more robust robber flies (Asilidae),
bee flies (Bombyliidae, 245 ), hover flies
(Syrphidae), and horse flies (Tabanidae)
are all represented too. One of the most
interesting of the house fly family Muscidae
is Glossina , the tsetse fly. This blood-
sucking, disease carrier of modern Africa is
represented by two species at Florissant.
Caddis flies (Trichoptera) have aquatic
larvae which build protective cases out of
sand and vegetation, sewn together with
silk. Many species are known from
Florissant. The most beautiful insects alive
today, the butterflies and moths
(Lepidoptera) do not fossilize well or, at
least, their coloration is lost. One of the
finest specimens of a fossil butterfly,
Prodryas persephone ( 218 ), is from
Florissant. This butterfly preserves no color
but its markings can be seen. It belongs to
the Nymphalidae (admirals, fritillaries,
tortoiseshells, painted ladies), as do some
other species at Florissant. There are
representatives of other lepidopteran
families too, including the cossid moths
with wood-boring larvae, silkmoths
(Saturniidae), and even a fossil caterpillar
has been found.
245
245 The bee fly Pachysystrophus rohweri
Diptera: Bombyliidae YPM. Length,
including proboscis, 16 mm 0.6 in.
 
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