Possible Mutualism Between Females of the Subsocial Membracid Polyglypta Dispar (Homoptera) Author(S): William G

Possible Mutualism between Females of the Subsocial Membracid Polyglypta dispar (Homoptera) Author(s): William G. Eberhard Source: Behavioral Ecology and Sociobiology, Vol. 19, No. 6 (1986), pp. 447-453 Published by: Springer Stable URL: http://www.jstor.org/stable/4599982 . Accessed: 07/09/2011 09:37 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Springer is collaborating with JSTOR to digitize, preserve and extend access to Behavioral Ecology and Sociobiology. http://www.jstor.org Behavioral Ecology Behav Ecol Sociobiol (1986) 19:447-453 and Sociobiology <0 Springer-Verlag1986 Possible mutualism between females of the subsocial membracid Polyglypta dispar (Homoptera) William G. Eberhard Smithsonian Tropical Research Institute and Escuela de Biologia, Universidad de Costa Rica, Ciudad Universitaria, Costa Rica Received April 18, 1986 / Accepted August 28, 1986 Summary. Female Polyglypta dispar membracids Study site and methods facultatively guard egg masses or oviposit into Polyglypta dispar (Fowler) is a large membracidfound on the masses guarded by other females. Defending weedy shrubs Montanoa hibiscifolia,and Verbesinaturbacensis females repel at least some enemies of both eggs (both Compositae). Observations were made on the principal and nymphs. Eggs of guarding females may be par- host, M. hibiscifolia,during the latter part of the rainy season tially protected from parasitism by the presence from 13 July to 19 October, 1982 near San Antonio de Escazu, Costa Rica (1350 m elevation). Eggs, nymphs, and attending of additional eggs laid by other females. Females females were checked daily or every other day during most sometimes desert egg masses or groups of nymphs, of this period, usually in the morning. Four differentM. hibisci- and undefended masses are sometimes adopted by folia plants within a 10 m radius were surveyed regularly, and other females. Some individuals remain on or near three others sporadically. M. hibiscifoliais a weedy perennial that is common in disturbed habitats in the Central Valley the plant where they grew up, and littermates of Costa Rica. It usually sheds some leaves and flowers early sometimes oviposit into the same egg mass. Some in the dry season, and vegetative growth is concentrated in copulating pairs are littermates, while others are the wet season, but plants generally have some green leaves not. Females with larger numbers of mature and year-round.Many plants near the study site and also at another nearly mature eggs in their ovaries are less likely site 12 km away with many M. hibiscifoliaplants lacked membracids. Membracidswere individuallymarked with fast drying to defend egg masses, and females desert smaller model airplanepaint. groups of nymphs more often. Newly molted adults were captured in vials, marked, and returned to the same leaf. Rechecking showed that this treat- ment did not cause the adult to abandon the leaf when marking was done in the first 3 days of an adult's life. The accounts below of newly moulted adult behavior are of individuals marked in the first three days of adult life. Introduction Dissections of ovaries of freshly killed and newly thawed females that were killed by freezing were performed in saline Subsocial behavior (postovipositional parental be- solution on a glass slide. Large, partially translucent eggs havior that promotes the survival, growth or devel- >1 mm long were classified as "mature or nearly mature". Some of these were found in the oviducts, and others in the opment of offspring) has evolved many times in lower parts of ovarioles. In one female that had been oviposit- a wide variety of insects, and is particularly com- ing when collected, some of the translucenteggs in the oviduct mon in the homopteran family Membracidae (re- were covered by a thin whitish membrane. Other eggs, termed views by Eickwort 1981; Tallamy and Wood 1986). " developingeggs ", were pearly white in appearanceand ranged interactions between subsocial from 0.1 to <9 mm long. Developing eggs occurred only in Cooperative par- the ovarioles. The amount of fat on the female's body wall ents are much less widespread taxonomically, be- was estimated visually. Spermathecaeof known virgins were ing frequent only in the Hymenoptera (Wilson all flat and clear white in color; the other spermathecalforms 1971). This paper reports on possible cooperation (ovoid, spherical, ovoids in various states of collapse) all had in a subsocial membracid in which females guard dark material inside, and were taken to indicate that insemina- tion had occurred. eggs and nymphs. Some females oviposit in the Egg masses from which all membracidsand parasites had egg masses of others, and both females may benefit emerged were teased apart egg by egg. A brownish membrane as a result. on the otherwisewhite inner surface of the egg and an irregular 448 "chewed" emergal hole instead of the clean split at the egg's on the periphery (P<0.01 with Chi Squared Test) tip left by membracidnymphs were used as indicators of para- (average rates of parasitism were 34?16% and sitism (eggs containing wasp pupae had this membrane). Eggs 38+19% in the center and the while from which neithermembracids nor parasiteshad emergedwere periphery, classified as undeveloped. Observationsof the minute parasitic average rates of undeveloped eggs were 14 + 11 and wasps were made in the field using a magnifying lens mounted 20+16% respectively). on a headband magnifiergiving a 10 x magnification. Defense against some large predators of There is some uncertaintyregarding species classifications nymphs was more effective; I saw females success- in the genus Polyglypta. Metcalf and Wade grouped the form in this study with others under the name P. costata (T.K. Wood, fully chase off three coccinellid beetles which personalcommunication), but I have followed the older classifi- preyed on nymphs. They did not respond however cation of Fowler because some of the different morphological to syrphid larvae attacking their nymphs, perhaps forms of Metcalf and Wade's " costata " consistentlyoccur sym- because no alarm pheromone was released (Nault patrically but are associated with different plant species (Eber- et al. 1974). Defensive behavior was dangerous, as hard, in preparation),and the male genitalia are slightly different. I saw defending females succumb to attacks by All averages are followed by + 1 standarddeviation. a reduviid bug and a salticid spider. Two other predators attacked nymphs (an adult staphylinid beetle, and a larval chrysopid (Neuroptera)), and Results at least four other species preyed on unguarded eggs (three mirid bugs and an unknown predator 1. Guardingbehavior which ate large chunks out of egg masses - perhaps Most egg masses and many groups of nymphs were a katydid?). accompanied by an adult female. Guarding did not There were apparently 5 nymphal instars. Av- preclude feeding, as some brooding females were erage estimated durations of first through fourth seen with the proboscis inserted into the central instars in the field were, respectively, 5, 4, 6 and vein of the leaf. These sites may not be ideal feed- 8 days. These data are only approximate since indi- ing sites, however, as most solitary males and fe- vidual nymphs were not marked. Nymphs, like males not associated with offspring were seen on adults, fed on the lower surfaces of leaves. They younger leaves. Females near egg masses or groups tended to cluster with other nymphs. The usual of nymphs gave several apparently defensive re- presence of an egg mass near groups of younger sponses when other insects or large objects ap- nymphs and the relative uniformity of sizes of proached. In contrast to nonguarding females, a nymphs within most groups suggested that many female with eggs was unlikely to move away even aggregations were composed of individuals that when prodded and pinched with forceps. Often a had hatched from the same mass. There were occa- defending female responded by buzzing her wings, sional mismatches of nymphal sizes within an ag- giving strong lateral kicks at the object with a hind gregation or abrupt increases in the numbers of leg, or sidling toward the object, and swinging the larger instar nymphs in a group from one day to posterior end of her pronotum laterally, on occa- the next, however, indicating that some groups had sion hitting it. members that came from different egg masses. Females interacting with the small egg parasite Nymphs sometimes moved to other leaves, but Gonatocerus sp. shuddered their bodies, shuffled adult females showed no signs of guiding the their feet, and sometimes turned 1800. They seemed nymphs' movements as do other membracids(Tal- unable, however, to keep track of the wasp, and lamy and Wood 1986). in general the defense seldom resulted in the wasp leaving the egg mass. Rates of parasitism of eggs 2. Desertions and adoptions were higher in one study area (average 26.3% in 4375 eggs from 14 masses) then another about Females deserted eggs and nymphs after varying 1 km away (< 5% in each of 7 masses). lengths of time (Table 1). Offspring were never Rates of parasitism in different regions of egg guarded until the nymphs became adults. Since in masses were probably not uniform. Each egg mass large masses the oldest nymphs were often at least was divided into central and peripheral areas using two moults ahead of the youngest, many nymphs the maximum width of the mass (w) as a reference: were abandoned at younger ages than those in Ta- all eggs within w/3 of the edge were classed as ble 1.

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