DOI: 10.5061/dryad.gtht76ht5
title: Defensive phragmosis and cathaptosis in Trichoptera larvae

description: Phragmosis, or the use of specially modified body parts and associated
 behaviors to block an opening as defense against predators, is a commonly
 observed phenomenon in certain ants and termites that block entrances of
 their subterranean nests with large, flat heads. It has been reported in
 some beetles and other insects and even in some frogs. Common features of
 phragmosis in caddisfly larvae include a hard and usually flat body
 surface, with or without stout spines, and the behavior of fitting that
 body surface tightly in the opening of its case. A different defensive
 strategy occurs in snails and case-making larvae of camptosomate leaf
 beetles (Chrysomelidae: Cryptocephalinae and Lamprosomatinae) that protect
 themselves from predators by securing the openings of their shells or
 cases firmly against the substrate, a behavior we call “cathaptosis.”
 Common features of cathaptosis in caddisfly larvae include a case with its
 vulnerable opening oriented parallel with the substrate and accompanied by
 behavior that grips the substrate, fixing the case opening firmly against
 it when threatened. We suggest that these defensive strategies have
 evolved multiple times in Trichoptera, especially in case-making larvae.
 We demonstrate some examples and provide tentative lists of caddisflies
 whose larvae may have evolved these defensive strategies.
description: To test our hypothesis for phragmosis, we observed the
 predator-prey interaction of case-making larvae of two Trichoptera species
 found locally in the Southern Appalachian Mountains when confronted with
 predators common in their habitats. The larva of <em>Goera
 calcarata</em> Banks, 1899 (Goeridae) makes a tubular case with
 lateral ballast stones for stability in fast-flowing water as it scrapes
 periphyton from the top surfaces of rocks in lotic-erosional habitats
 (Wiggins 1996). The larva of <em>Fattigia pele</em> (Ross,
 1938) (Sericostomatidae) makes a case of fine sand and burrows in the sand
 of mountain springbrooks to gather fine organic particles (Wiggins
 1996).  Mature larvae of <em>G.
 calcarata</em> were collected from the tops of stones in a
 first-order stream at 34°45.366’N; 82°51.372’W, ca. 300 m a.s.l., and
 young larvae of <em>F. pele</em> were sifted from sand in a
 springbrook at 35°22.2’N; 83°6.6’W, ca. 1,520 m a.s.l. Available predators
 at those sites included larvae of <em>Acroneuria abnormis</em>
 (Newman, 1838) (Plecoptera: Perlidae) and <em>Corydalus
 cornutus</em> (Linnaeus, 1758) (Megaloptera: Corydalidae). Specimens
 of both the Trichoptera and the predators were transported back to the
 laboratory with stream water in separate plastic bags on ice and were kept
 alive and starved in refrigerated stream water until their interactions
 could be documented a few days later.            The
 observation arena was a wide glass dish filled with stream water. A
 caddisfly and a predator were introduced into the arena and observed for a
 few minutes as they warmed to room temperature. We observed and recorded
 the interactions through a Celestron Microscope Pro® Model #44308 attached
 to a computer.        To test our hypothesis of
 cathaptosis, we observed the case and behavior of a Chinese species
 of <em>Ascalaphomerus</em> Walker, 1852 (Calamoceratidae).
 Larvae of an <em>Ascalaphomerus</em> species were captured on
 pieces of wood in a pool of a mountain creek (P.R. China: Zhejiang
 Province, Li-shui City, Yun-he County, Dian-qing-shan Village, Yun-tan-xi
 Stream 28°9.72’N; 119°41.532’E, ca. 320 m, 9 August 2022) and brought with
 the wood to the laboratory for testing. Leaf litter, stones, and woody
 debris (twigs) were placed with the larvae in a rearing chamber. Instead
 of using a living predator, we gently agitated a test animal with a probe.
 The response of the larva was recorded with an Olympus TG-6 digital camera
 (Olympus, Beijing, China).
description: # Defensive phragmosis and cathaptosis in Trichoptera larvae
 The four videos in this
 dataset show behavioral responses of Trichoptera larvae to predatory
 threats, including evidence of phragmosis by *Fattigia pele*
 (Sericostomatidae) and *Goera calcarata* (Goeridae) and of cathaptosis by
 *Ascalaphomerus* sp. (Calamoceratidae). ## Description of the data and
 file structure When disturbed by a potential predator, a larva of
 *Fattigia pele* or *Goera calcarata* withdraws into its protective
 portable case, blocking the case entrance with a hard and usually
 flattened head or head-and-thoracic notum, demonstrating phragmosis. When
 disturbed by a potential predator, a larva of *Ascalaphomerus* sp. grasps
 the substrate, forcing the entrance of its protective portable case
 against the substrate to exclude the predator, demonstrating cathaptosis.
 ## Sharing/Access information Links to other publicly accessible locations
 of the data include the following: *
 *
 *
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 ## Code/Software The
 videos are recorded in MP4 software.