Differences in prey capture strategies by obligatory pitfall builders and facultative pitfall builders; it describes also their differences in energy and prey consumptions.

1. Abstract
Antlion larvae are well known as voracious insect predators that in principle are
dependent on funnel-like traps dinged by themselves, on the bottom of which they sit
and wait for strong temporal and spatial irregular prey. From the wildlife - especially
from the insect world, it is well known that both the construction of prey capture traps
and the installation of a funnel-like catching traps are no novelty since these practices
have evolved in different groups independently of one another. The predatory behaviors
of the larvae of ant lion are often discussed differently and contradictorily as well. Firstly,
the main publications on ant lion prey capture behaviors describes only the obligatory
pitfall construction (= sit-and-wait prey catching strategy). On the other hand, the
literature has classified another strategy which is known as active foraging strategy by
which the larvae capture the prey item pursuing and catching them actively on the sand
surface. Newly, researchers draw attention to an intermediate predation strategy in
which the larvae catch their prey by both the facultative constructed funnel as well as
by an active hunting. Finally, the debates are concerned with the question, how these
strategies are used in the actualgenesis and ontogenesis, if the different prey capture
strategies are indeed - as suggested by some authors, only alternative behaviors that
depends on the biological status of the individual and of the actual ecological
constraints. The main objective of these experiments was to prove the independent
occurrences of both obligatory and facultative pit construction behavior, and further
more they were intended to assess their energetic, behavioral and morphological
differences on the basis of field and laboratory studies. The investigated ant lion larvae
were exclusively the L3 instar of both foraging strategies (obligatory and facultative pit
construction). The serial experiments enabled the registration of the larval behavior
both with and without prey consumption. These experiments have also enabled the
registration of different parameters of the larvae behavior with and without pitfall as
well as with and without free locomotion, what made possible the energetic assessment
and appraisal. In principle, with concern to the investigated parameters (weight gain or
loss, extraction rate, pitfall dimensions) the results show significant differences between
larvae from these strategies, both in the field and in the laboratory. So, for example, the
sit-and-wait larvae had more extraction rates than the facultative pit builders. Similarly,
larvae with the obligatory funnel building strategy built larger funnel than the ones from
the other foraging strategy. When the larvae were not fed and they could not build the
Behavioral, and bioenergetics, and morphological characteristics of the ant
lion larvae with respectively obligatory (sit-and-wait) and facultative pit
building strategies under natural and laboratorial conditions
(Myrmeleontidae, Neuroptera, Insecta)
Pires, Cristiano
Department of Biology, Faculty of Natural Science and Mathematics, Pedagogical University, Maputo,
Mozambique

2. pitfalls but they could move epi- or sub terrestrial, the mass decrease rate was higher in
larvae of facultative pit building strategy although a same mass loss profile. It became
also clear that the locomotion of the larvae is associated with higher energy costs in
both strategies compared to the funnel construction costs. Further differences exist with
respect to the length of the locomotor extremities, the tooth pattern in de inner side of
the mandible, the construction of the mandible and the head capsule width. All
investigated characteristics exhibit constancy and homogeneity within the respective
strategies.
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Key words: Ant lions, larvae L3, predator, prey, foraging strategies, funnel, sit-and-wait
prey catch strategy, intermediate foraging strategy, facultative pitfall construction,
active foraging strategy, energy costs, locomotion, mass loss profile