Leaf trenching by Indian red admiral caterpillars for feeding and shelter construction

Abstract

Many folivorous insects sever leaf veins, trench across leaf blades, or girdle petioles prior to feeding on leaves. The purpose of these behaviours is generally thought to be sabotage of the anti‐herbivore chemical defences of host plants. For insects that construct leaf shelters, these behaviours may make leaves easier to roll or fold. Larvae of the Indian red admiral butterfly, Vanessa indica (Herbst), cut trenches at the base of host plant leaves and construct leaf‐fold shelters. I attempted to determine which of the above functions the trenching behaviour of V. indica larvae serves. If the function of trenching is to facilitate leaf‐folding, then larvae should cut trenches before folding leaves. When the larvae used larger leaves, they tended to trench them prior to folding them. This suggests that the function of trenching behaviour is to make leaves easier to fold. However, larvae sometimes cut trenches after folding the leaves, suggesting that this behaviour has additional functions. When the larvae were about to moult or pupate, they did not cut trenches, suggesting that trenching behaviour may also be involved in feeding.

Shelter-Building Behavior and Natural History of Two Pyralid Caterpillars Feeding onPiper stipulaceum

“…However, caterpillars trench the petiole in spite of the predation cost involved, suggesting that it confers additional benefits. Trenching is likely to facilitate the rest of the shelter-building process because it provokes a turgidity loss that facilitates leaf folding (Ide 2004;Hansell 2005). It may also have a nutritional function, since Lepidomys caterpillars feeding inside their shelters have been observed to have higher pupal mass than caterpillars feeding on non-trenched tissue (Abarca and Boege 2011).…”

“…Caterpillars also follow a stereotyped silking pattern, building standardized shelters of the same size and shape according to the species and its developmental stage (Lind et al 2001;Darling 2003;Greeney and Jones 2003;Weiss et al 2003). Ontogenetic restrictions in shelterbuilding behavior are mainly due to mandible size and strength, which determine the caterpillar's ability to cut and fold foliage and also restrict its feeding habits (Hochuli 2001;Greeney and Jones 2003;Weiss et al 2003;Ide 2004). Therefore, shelter building is often restricted to the later larval instars (Gaston et al 1991).…”

“…Detailed descriptions of the shelter-building habit are available for various species such as the rice leaf folder, Caloptilia serotinela (Lepidoptera: Pyralidae) (Fraenkel and Fallil 1981); the red admiral caterpillar, Vanessa indica Herbst (Lepidoptera: Nymphalidae) (Ide 2004); and several skippers (Hesperiidae), such as the silver-spotted skipper, Epargyreus clarus Cramer (Lepidoptera: Hesperiidae) (Weiss et al 2003) and Falga jeconia ombra Evans (Lepidoptera: Hesperioidea) (Greeney and Warren 2009). The diversity of shelters and the shelter-building techniques used for their construction are still largely underrepresented in the literature, and little is known regarding leaf selection and natural history constraints to shelter building, particularly in tropical systems.…”

Do canal-cutting behaviours facilitate host-range expansion by insect herbivores?

“…by trapping photosynthates in the leaf) and/or alter water content. Unfortunately, only a few studies have examined the function of canal cutting on plants lacking exudates (Ravenscroft, 1994; Fitzgerald, 1995; Ide, 2004). Interestingly, most of the insects exhibiting these behaviours are specialists.…”

“…Interestingly, most of the insects exhibiting these behaviours are specialists. Notable examples include 11 species of heliconiines that trench Passiflora , plus various arctiid, ithomiine, lycaenid, saturniid, skipper and sphingid caterpillars and sawfly larvae (Mackay & Wellington, 1977; Dussourd, 1993 and references cited; Ravenscroft, 1994; Ide, 2004; Albanese et al. , 2007).…”