# Consequences of the instar stage for behavior in a pit-building antlion

> Two antlion larvae can weigh exactly the same and still behave like different animals. In this laboratory study from Israel, larvae in their final larval stage dug bigger pits, struck faster at prey and ate more of each meal than younger larvae of the same weight, until the younger ones moulted and caught up. The authors argue that size alone can hide important differences between individuals.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2014-alcalay-barkae-consequences-instar-stage-behavior/

## Citation and access

- **Authors:** Yehonatan Alcalay, Erez David Barkae, Ofer Ovadia and Inon Scharf
- **Year published:** 2014
- **Journal or source:** Behavioural Processes
- **Full citation:** Alcalay, Y., Barkae, E. D., Ovadia, O. and Scharf, I. 2014. Consequences of the instar stage for behavior in a pit-building antlion. Behavioural Processes 103: 105–111.
- **DOI:** 10.1016/j.beproc.2013.11.009
- **Access status:** Publisher link only
- **Where to find it:** https://doi.org/10.1016/j.beproc.2013.11.009

## Tags

- **Species:** Invertebrates > Antlion
- **Region:** Asia > Israel
- **Behaviour and ecology:** Behaviour; Feeding; Hunting; Movement; Predation
- **Methods and technology:** Analysis of variance (ANOVA); Direct observation; Pearson correlation
- **Data type:** New field data
- **Observer qualification:** Not needed
- **Discipline:** Behaviour and ecology
- **Year published:** 2014

## Detailed keywords

- **Species:** Studied: pit-building antlion larvae, Myrmeleon hyalinus (Neuroptera: Myrmeleontidae), second and third instar (larval stage). Prey offered: flour beetle larvae (no scientific name given). Other insects and spiders are discussed from the literature only.
- **Location and habitat:** Larvae collected under tamarisk trees at Nahal Secher (31°06’N, 34°49’E), a sandy area 15 km south of Beer-Sheva, Israel. The species prefers to build pits in shaded spots under trees or bushes in sandy soils. All tests were done in the laboratory, in cups and trays of sand.
- **Topics:** animal personality; behavioural consistency; behavioural syndromes; larval (instar) stage versus body mass; pit building and pit size; response time to prey; prey exploitation efficiency (how much of each prey item is eaten), compared with giving-up density (GUD); pit relocation before and after disturbance; morphology (head width, mandible length, abdomen width) and behaviour; sit-and-wait (trap-building) predators; state-dependent models and risk-prone foraging before the reproductive stage.
- **Statistics or models:** t-test; repeated-measures analysis of variance (ANOVA); one-way ANOVA; discriminant analysis; Pearson and Spearman rank correlations; principal component analysis (PCA) with Z-score transformation; square-root transformation of skewed data. Software: SYSTAT 12 and MATLAB 7.8. Small inconsistencies in the paper: (1) the Methods say the principal components were correlated with “mandible width”, but the trait measured and reported in the Results is mandible length; (2) the Methods describe “five” separate ANOVAs for experiment 2, which matches four behaviours only if relocation before and after disturbance are counted separately.
- **Data type:** New data from laboratory experiments on field-collected larvae. Collection and test dates are not given (the paper was received in April 2013). Experiment 1, phase 1 lasted four weeks; phase 2 lasted two and a half weeks and started 10 weeks after phase 1.

## Synopsis

### 1. What they did

Antlion larvae are small insect predators that dig cone-shaped pits in loose sand and wait for ants and other small arthropods to tumble in. Like other insects, they grow through stages called instars, moulting between each. Antlions have three larval instars, and the third is the longest, more than half the larval period. Researchers often match animals by body mass and assume similar-sized individuals are alike. The authors asked whether larvae of the same mass but a different instar behave differently.

They collected larvae of Myrmeleon hyalinus, the most common pit-building antlion in Israel, near Beer-Sheva, and tested them in the laboratory. Before each experiment the larvae were fed, weighed and then starved for seven days so they started in the same condition. They measured four behaviours:

- Pit size: pit diameter.

- Response time to prey: how long a larva took to throw sand at a flour beetle larva placed at the edge of its pit (60 seconds if it did not respond).

- Relocation: how far a larva moved its pit over 48 hours in a larger tray of sand in the dark, and again 24 hours after the researchers wiped out its pit and traces (a disturbance like wind, rain or animals passing).

- Prey exploitation efficiency: the weight a larva gained from one prey item, divided by the weight of the prey.

Experiment 1: 50 larvae of very similar mass (about 6 mg), 29 in the second instar and 21 in the third, told apart by head width and mandible length. They were tested once as they were, and again after the second instar larvae had moulted into the third instar. They also measured head width, mandible length and abdomen width, to see whether body shape predicted behaviour.

Experiment 2: 60 second instar larvae, split into small (early) and large (late) groups. The small ones were tested again after they had been fed and grown.

### 2. What they found

Same weight, different stage (experiment 1)

- Third instar larvae built bigger pits, responded faster to prey and ate a larger share of each prey item than second instar larvae of almost the same mass.

- These differences disappeared once the second instar larvae had moulted into the third instar.

- Relocation distances did not differ between the stages, but all larvae moved further in the first phase.

- Pit size separated the two stages best, followed by prey exploitation efficiency and relocation distance; response time separated them least.

Consistent individuals (third instar larvae)

- Each larva’s pit size and response time were consistent between two trials.

- Relocation distance after disturbance was consistent, but not before disturbance. Prey exploitation efficiency was not consistent.

- Behaviours fell along two axes. The first linked big pits, fast responses and eating more of each prey item: larvae that invested more in foraging. The second linked slow responses to prey with moving pits further.

- Head width, mandible length and abdomen width did not predict either axis.

Small versus large second instar larvae (experiment 2)

- Small second instar larvae responded faster to prey and moved further after disturbance than large ones. Pit size, prey exploitation and relocation before disturbance did not differ.

- When the same small larvae had grown larger, still in the second instar, their behaviour had not changed significantly.

- So larvae of different stages and similar mass differed more than larvae of the same stage that differed in mass by over 60%.

### 3. What they concluded

- Animals of similar size, especially those collected in the field, are not necessarily alike. Instar stage predicted antlion behaviour better than body mass within an instar.

- Studies of insect larvae should record instar stage as well as body mass and include it in their design and analysis; ignoring it could make stage differences look like individual personality.

- Third instar larvae, which must store resources for adult reproduction, seem to invest more in foraging, as state-dependent models predict.

- The link between larger larvae and larger pits is probably due to head and mandible size, which differ between instars, rather than total body mass. Within the third instar, body shape had little effect, perhaps because hunger, density, sand type, temperature and experience shape pit size more.

- Larvae remained consistently different even within the same instar. The authors suggest studying physiology, such as metabolic rate, and behaviour across different situations.

### 6. Other technologies, skills or innovations

- Instar stage identified from a plot of head width against mandible length, measured from stereoscope photographs with the free program ImageJ.

- Simple laboratory measures of foraging: pit diameter with a digital caliper, response time to a standard prey item, and weight gain from one prey item on an analytical scale.

## Cite this summary

Lawrence, K. 2026. Summary of: Consequences of the instar stage for behavior in a pit-building antlion (Alcalay and Barkae et al., 2014). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2014-alcalay-barkae-consequences-instar-stage-behavior/