Larvae Protected From Predators

a black and orange insect stands on a plant against a green background

Biological Strategy

Case-bearing leaf beetles

AskNature Team

Image: Katja Schulz / Wikipedia Commons / CC BY - Creative Commons Attribution alone

Protect From Animals

Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.

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Manage Impact

An impact is a high force or mechanical shock that happens over a short period of time, such as a hammer hitting a nail rather than a hand pushing slowly against a wall. Because of their speed and force, impacts don’t allow materials to slowly adjust to the force, which can lead to cracks, ruptures, and complete breakage. Therefore, living systems have strategies that can absorb, dissipate, or otherwise survive that force without the need to add large amounts of material. For example, the Toco toucan’s large beak is very lightweight, yet can withstand impacts because it’s made of a composite material with rigid foam inside and layers of a hard, fibrous material outside.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Larvae of case-bearing leaf beetles protect themselves with hard cases made of fecal matter.

“Animals create a wide variety of structures to deal with and
challenges. We evaluated an intriguing structure whose function
has never been thoroughly tested. Specifically, we evaluated the
hypothesis that the body-enclosing ‘faecal case’ created and lived in by
the immature stages of Neochlamisus leaf beetles reduces their
risk of predation. We especially focus on the case of N. platani,
which is externally covered with host-plant trichomes, and includes a
distinct trichome-filled chamber (‘attic’) in the case apex. Here, we
separately evaluated the effects of case, trichomes and attic on each of
several behavioural stages of predator attack using N. platani
and N. bimaculatus larvae and pupae. Three generalist predators
(crickets, soldier bugs and lynx spiders) that represent different
feeding strategies were used in our individual-level repeated
observation behavioural trials. Results strongly demonstrated that the
faecal case itself greatly reduced predation risk for all combinations
of beetle species, life history stage and predator. Additional evidence
indicated that both trichomes and attics further and independently
reduced predation risk. Variation in results among treatments was also
informative. For example, the capacity of faecal case components to
reduce predation sometimes varied markedly among predators and between
larval versus pupal life stages. Patterns of predator behaviour provided
no evidence that caseless larvae have alternative means of defence.
This study further presents a rare example of the co-option of a
physical plant defence (trichomes) by an herbivore.” (Brown & Funk 2010:127)

“As excrement goes, the beetles produce remarkable stuff, Funk says.
Despite weeks of wear, it stays firm and fungal-free. To a human nose it
doesn’t smell and, after some complicated moments trying to collect
larvae, Funk can add that it doesn’t have a discernible taste either.” (Milius 2009)

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-4XMC05H-2&_user=10&_coverDate=01%2F31%2F2010&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1330158264&_rerunOrigin=scholar.