HABITAT SELECTION BY AQUATIC INVERTEBRATES
329
but by moving in straight lines. Animals removed to any point within
30-100 cm are able to return to their own hole. They will also home
after having been kept in the laboratory for 24 hours. Animals whose
oral lappets are removed cannot home. The oral lappets are constantly
in touch with the algal carpet which therefore may give Onchidium some
chemical clues of its whereabouts. There are other air-breathing
invertebrates in the intertidal zone (e.g. Petrobius maritimus (Leach),
Thysanura), and much of the crevice fauna on the shore is essentially
terrestrial. If these animals emerge from their holes or crevices for food
or to explore when the tide is out, they may also home, and must
at any rate behave in a way that will return them to some shelter as the
tide rises (Cameron, 1966; Craig, 1970). The homing of limpets on to
their own rock scars is we11 known (Wells, 1917; PiBron, 1919; Thorpe,
1956, pp. 186-191). Cook et al. (1969) have recently attempted to determine its mechanism, but experienced difficulty in finding conditions that
would inhibit it (Fig. 5). The problem appears to be difficult, but
would be worth further detailed study under more stringent laboratory
conditions. It would be interesting to know, for instance, whether
limpets could be taught to recognize an artificial scar on a flat surface
of say wood or brick.
I. Oviposition preferences
Aquatic invertebrates that lay their eggs on particular surfaces or
in particular sediments must presumably choose a site for oviposition,
and their choice will obviously define the distribution of their young.
Examples are caddis flies (Trichoptera), dragonflies (Odonata), mayflies
(Ephemeroptera) and notonectids (Hemiptera) in fresh water and
cephalopods, some gastropods, and some polychaetes in the sea, and
there are many others. Little is known of the oviposition preferences
of any of those animals in contrast to the many studies on terrestrial
insects. Craig (1970) refers, in passing, to the intertidal beetle Thinopinus pictus preferring wetter sand for oviposition. Hudson (1956) who
has studied the oviposition of mosquitoes, offered Culex pipiens
molestus ForskU and Aedes aegypti (L.) salt solutions of different
concentrations and counted the numbers of rafts of eggs and also the
numbers of individual eggs laid. Solutions of greater than 0.085 M were
avoided. The behaviour of the two species will obviously prevent them
from laying eggs on the surface of brackish waters. In a more recent
paper Hudson and McLintock (1967) showed how Culex tarsalis
Coquillet preferred to oviposit on water containing pupae, exuviae, or
emerging adults of their own species, rather than water containing
other related species, a nice analogy to the chemical basis of gregarious-
329
but by moving in straight lines. Animals removed to any point within
30-100 cm are able to return to their own hole. They will also home
after having been kept in the laboratory for 24 hours. Animals whose
oral lappets are removed cannot home. The oral lappets are constantly
in touch with the algal carpet which therefore may give Onchidium some
chemical clues of its whereabouts. There are other air-breathing
invertebrates in the intertidal zone (e.g. Petrobius maritimus (Leach),
Thysanura), and much of the crevice fauna on the shore is essentially
terrestrial. If these animals emerge from their holes or crevices for food
or to explore when the tide is out, they may also home, and must
at any rate behave in a way that will return them to some shelter as the
tide rises (Cameron, 1966; Craig, 1970). The homing of limpets on to
their own rock scars is we11 known (Wells, 1917; PiBron, 1919; Thorpe,
1956, pp. 186-191). Cook et al. (1969) have recently attempted to determine its mechanism, but experienced difficulty in finding conditions that
would inhibit it (Fig. 5). The problem appears to be difficult, but
would be worth further detailed study under more stringent laboratory
conditions. It would be interesting to know, for instance, whether
limpets could be taught to recognize an artificial scar on a flat surface
of say wood or brick.
I. Oviposition preferences
Aquatic invertebrates that lay their eggs on particular surfaces or
in particular sediments must presumably choose a site for oviposition,
and their choice will obviously define the distribution of their young.
Examples are caddis flies (Trichoptera), dragonflies (Odonata), mayflies
(Ephemeroptera) and notonectids (Hemiptera) in fresh water and
cephalopods, some gastropods, and some polychaetes in the sea, and
there are many others. Little is known of the oviposition preferences
of any of those animals in contrast to the many studies on terrestrial
insects. Craig (1970) refers, in passing, to the intertidal beetle Thinopinus pictus preferring wetter sand for oviposition. Hudson (1956) who
has studied the oviposition of mosquitoes, offered Culex pipiens
molestus ForskU and Aedes aegypti (L.) salt solutions of different
concentrations and counted the numbers of rafts of eggs and also the
numbers of individual eggs laid. Solutions of greater than 0.085 M were
avoided. The behaviour of the two species will obviously prevent them
from laying eggs on the surface of brackish waters. In a more recent
paper Hudson and McLintock (1967) showed how Culex tarsalis
Coquillet preferred to oviposit on water containing pupae, exuviae, or
emerging adults of their own species, rather than water containing
other related species, a nice analogy to the chemical basis of gregarious-