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PSYCHE

A Journal of Entomology

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This is the CEC archive of Psyche through 2000. Psyche is now published by Hindawi Publishing.

Shin-ichi Kudo.
Observations on Lepidopteran leaf-shelters as molting refuges for the stink bug Elasmucha putoni (Heteroptera: Acanthosomatidae).
Psyche 101(3-4):183-186, 1994.

This article at Hindawi Publishing: https://doi.org/10.1155/1994/12083
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OBSERVATIONS ON LEPIDOPTERAN LEAF-SHELTERS AS MOLTING REFUGES FOR THE STINK BUG ELASMUCHA PUTONI (HETEROPTERA: ACANTHOSOMATIDAE)
Laboratory of Applied Zoology
Faculty of Agriculture
Hokkaido University
Sapporo, 060 Japan
When molting to the adult, the acanthosomatid bug Elasmucha putoni form aggregations on the wild mulberry Moms bombycis. The 5th-instar nymphs and/or newly molted adults were found more often in leaves rolled, folded, or tied by tortricid larvae than on unmodified leaves. Bugs probably seek protection in lepi- dopteran leaf-shelters during molting.
Many lepidopteran species build shelters by rolling, folding or tying leaves together with silk. Such leaf-shelters have been shown to provide a variety of benefits to herbivores (e.g., Damman, 1987; Sagers, 1992; Cappuccino, 1993). Herbivores other than shelter- makers, such as lepidopteran species which cannot build shelters of their own, homopterans, beetles and sawflies, also have been found in leaf-shelters (Can-011 & Kearby, 1978; Carroll et al., 1979; Cappuccino, 1993).
In the present report, I describe the use of lepidopteran leaf- shelters as adult-molting sites by the bug Elasmucha putoni Scott (Acanthosomatidae). This bug is a subsocial species: parent females guard their eggs and nymphs on the wild mulberry Moms bombycis Koizumi (Tachikawa, 1991). Nymphs live in aggrega- tions and feed on the host fruit in the daytime. Nymphal feeding aggregations become smaller with progress of the instar, and in the final 5th instar, nymphs often feed solitarily (Kudo, unpublished). Manuscript received 17 May 1994.
183
Pu&e 101: 183- 186 11994) hItp/@ychr rnlclub wg/101/101- I83 html



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184 Psyche [vo~. 101
MATERIALS AND METHODS
Field research was conducted in Misumai, Sapporo, on the island of Hokkaido in northern Japan in July 1991. Adult-molting aggregations or individuals of E. putoni, including 5th-instar nymphs molting or just before molting, andlor newly molted adults on the host tree, were examined. Rolled, folded, or tied leaves were opened and bugs (and other arthropods) contained within them were counted. The number of individuals per aggregation on unmodified leaves was also recorded. To learn the frequency of leaf-shelters, I randomly chose 30 branches with 10 to 20 shoots and counted all shelters and unmodified leaves. A total of 98 adult-molting aggregations or solitary bugs were found on mulberry trees, 63 of them in leaf-shelters and 35 on unmodified leaves. Of 73 leaf-shelters examined, 86.3% (n=63) contained at least one bug (Fig. 1). Some bugs were present on the outside surface as well as the inside surface of the shelters. Leaf- shelters were rare on mulberry: only 4.3% of 1142 leaves exam- ined were modified. The proportion of adult-molting aggregations (or individuals) in leaf-shelters to total aggregations (64.396, n=98) was apparently larger than that of shelters to total leaves (chi- square=388.1, p<0.0001), indicating that bugs seek shelter during the molting process. New adults left the shelters within one or two days after fully tanning. They stayed on the mulberry for a few days and then disappeared: they move to and breed on different plant species (Kudo, unpublished).
Most of the shelters were built by the lepidopterans, Olethreutes mori Matsumura or 0. morivorum Matsumura (Tortricidae). At the time of examination, no larvae or pupae existed in any of the lepi- dopteran shelters, although pupal exuviae left were found in some shelters. Two of the shelters examined were constructed by spiders: one without bugs contained a spider with an egg sac, and another without a spider contained four bugs. Three shelters contained sin- gle earwigs. Figure 2 shows frequency distributions for bugs per unmodified leaf and per leaf-shelter. There was no significant dif- ference in nymphal group size between the types of leaves (Mann- Whitney U test, p=0.645).




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19941 Kudo 185
Fig. 1. An adult-moltmg aggregation of Elasmuch puwm within an open Icaf- shelter.
Pig. 2. Comparison of nymphal group size on unmodified leaves and in Ieaf- she! ten.




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186 Psyche [vo~. 101
Living in a leaf-shelter may provide various benefits for hervi- vores, i.e., improved microhabitat or leaf quality (Hunter & Willmer, 1989; Sagers, l992), and refuge from predators (Damman, 1987; Cappuccino, 1993). Insects that utilize a pre-existing shelter may enjoy these benefits. In E. putoni, nymphs feed on the fruit of its host (Kudo, unpublished), and thus, gain no nutritional benefits while inhabiting leaf-shelters. On the other hand, molting and newly molted bugs with little mobility and soft cuticles are vulner- able to predators and harsh weather. Nabid bugs and thomisid and salticid spiders were sometimes observed to prey on late-instar nymphs or adults of E. putoni. It is very likely that leaf-shelters formed by tortricids provide molting and newly molted bugs pro- tection from predators or harsh weather. The presence of shelter- making lepidopterans, therefore, may indirectly increase bug survival.
I thank N. Kuhara for help with field work and T. Kumata for identification of the moths. Anonymous referee's comments improved the manuscript. This study was supported in part by a JSPS Fellowship for Japanese Junior Scientists, and by a Grant-in- Aid for Scientific Research from the Ministry of Education, Sci- ence and Culture, Japan.
Cappuccino, N. 1993. Mutual use of leaf-shelters by lepidopteran larvae on paper birch. Ecol. Entomol. 18: 287-292.
Carroll, M. R., and Kearby, W. H. 1978. Microlepidopterous oak leaftiers (Lepi- d0ptera:Gelechioidea) in central Missouri. J. Kansas Entomol. Soc. 5 1: 457-471. Carroll, M. R.; Wooster, M. T. Kearby, W. H., and Allen, D. C. 1979. Biological observations on three oak leaftiers: Psilocorsis quercicella, l? reftexella and P. cryptolechiella in Massachusetts and Missouri. Ann. Entomol. Soc. Am. 72: 44 1-447.
Damman, H. 1987. Leaf quality and enemy avoidance by the larvae of a pyralid moth. Ecology 68: 88-97.
Hunter, M. D., and Willmer, P. G. 1989. The potential for interspecific competition between two abundant defoliators on oak: leaf damage and habitat quality. Ecol. Entomol. 14: 267-277.
Sagers, C. L. 1992. Manipulation of host plant quality: herbivores keep leaves in the dark. Funct. Ecol. 6: 741-743.
Tachikawa, S. 1991. Studies on Subsocialities of Heteroptera in Japan. Tokyo Agri- cultural University Press, Tokyo. 167pp. (In Japanese)



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