Occurrence of Goldenrod Galls: Study of Insect Ovipositing Behavior
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How-To-Do-It Occurrence of Goldenrod Galls: study of Insect Ovipositing Behavior Sandra J. Newell Goldenrod galls are a valuable re- terminateher ovipositionbehavior, (2) Eurosta gall may occur on one stem, source for use in biology labs (Peard punctureonly the outer bud leavesand but they do not say how frequently Downloaded from http://online.ucpress.edu/abt/article-pdf/56/1/51/46455/4449743.pdf by guest on 29 September 2021 1992). Goldenrods and the associated rejectthe bud,or (3) continueher oviposi- multiple galls occur. It is unknown gall-forming insects are often abun- tionalprobe through additional bud leaves whether an ovipositing female can rec- dant in early stages of old-field succes- whichfrequently, but not always, results ognize that another female's egg has sion. In addition, these old-field habi- in the injectionof an egg into the bud. already been deposited in a particular tats can be accessible to groups of stem. students. The laboratory exercise de- Abrahamson et al. (1989) were able A second species of gall-maker scribed here takes advantage of this to demonstrate that E. solidaginis which is relatively common is Gnori- resource to explore a question con- exhibits a preference for Solidago moschemagallaesolidaginis, a goldenrod cerning the behavior of the female altissima, although S. canadensis, S. moth. Gnorimoschemaproduces an el- gall-forming insects as they lay eggs gigantea and S. rugosa support liptical swelling, approximately 2.5- on the goldenrod plant. populations of E. solidaginis in some 5 cm long, on the stem of the golden- The most common gall-makers on areas. Abrahamson et al. (1989) sug- rod. As in the spherical gall, the ellip- goldenrods are Eurosta solidaginis gest that the preference exhibited by tical gall contains one larva. The moth (Diptera: Tephritidae), Gnorimoschema the fly is based on both tactile and larva pupates in late-July, and the gallaesolidaginis (Lepidoptera: Gelechi- chemical information gained by the adult emerges in August or September idae), and Rhopalomyia solidaginis female while she is on the bud. In (Leiby 1922; Abrahamson & McCrea (Diptera:Cecidomyiidae). The golden- addition, Anderson et al. (1989) dem- 1986). After mating, the female ovi- rod gall fly, Eurosta solidaginis, pro- onstrated that E. solidaginis is able to posits on the lower leaves and stems duces a sphericalswelling (ball gall) on distinguish between susceptible and of goldenrod, and the eggs overwinter the upper stem of goldenrods, about resistant genotypes of S. altissima and in the leaf litter at the soil surface. 2.5 cm in diameter and containing a generally chooses the susceptible ge- Each Gnorimoschema female deposits single fly larva (Milne 1940). The larva notypes for oviposition. They were about 60 eggs (Leiby 1922). The larva pupates in early spring, emerging unable to specify a mechanism for this hatches in May, climbs up a new stem from the gall in April or May. Adult discriminatory ability, but susceptible of S. altissima to the apical meristem, flies mate, and females begin laying plants tend to be the faster growing and bores into the bud. It remains in eggs by late May (Miller 1959). Ovipo- plants. the bud, feeding for several days, then sition, the laying of an egg by the Females typically lay 70-75 eggs undergoes a molt (Leiby 1922). The female, was described in detail by (Milne 1940). Consequently, infesta- second instar burrows through the Abrahamson et al. (1989): tion rates tend to be high. For exam- apical meristem and down about 5- Prior to oviposition,an E. solidaginis ple, Milne (1940) collected 1000 gold- 8 cm into the stem (Leiby 1922; Abra- femaletypically climbs to the apex of the enrod stems and 264 stems had ball hamson & McCrea 1986). How the goldenrodbud and rapidlyrubs the apex galls. The egg of the goldenrod gall fly larva recognizes a goldenrod plant is with herforelegs, occasionally pulling the hatches soon after being deposited, unknown. Leiby (1922) says that the budtip to hermouth parts. If not discour- and the larva burrows through the larva "crawls aimlessly about until it aged by the informationthese activities apical meristem to produce the gall in comes in contact with a new golden- elicit, thefly walksdown to the baseof the the stem of the goldenrod. The gall rod shoot whereupon it crawls up the budand walksaround the basesearching appears by mid-June and grows in stem to the unfolding bud." Occasion- for a suitableplace to oviposit.If shefinds diameter until mid-July (Weis & Abra- ally, two Gnorimoschemagalls exist on a suitableoviposition site, she archesher hamson 1985; McCrea & Abrahamson one stem (Leiby 1922). It is unknown thoraxand abdomeninto ovipositionpos- 1987). The larva feeds on the gall tis- whether the larva can recognize the ture. With the ovipositortouching the sue through the summer, burrowing presence of another of its own species surfaceof the bud leaves, the fly can (1) an exit tunnel up to the epidermis of on the stem. Also, the larva burrows the stem (McCrea & Abrahamson into the apical bud at about the same 1987). In October the larva enters dia- time that the Eurosta females are ovi- Sandra J. Newell, Ph.D.,teaches biology pause, a resting stage in which the positing on the apex; and it is un- at Indiana Universityof Pennsylvania, In- larva overwinters (Weis & Abraham- known whether the two species can diana, PA 15705. son 1985). Cane and Kurczewski recognize that a stem is already inhab- (1976) indicate that more than one ited by the other species. OVIPOSITINGBEHAVIOR 51 Goldenrod Galls - Sample Data Sheet Transect# 1 StudySite # Date 10-1-91 X = gall present Stem # ballgall elpseall bunchgall Stem# ball ellipse gall bunchgall 1 X 351 X 2 __--______ 36 X 3 -} l } x 37 4 ___ X 38 r 5 ___ X 39 1X 6 x x 401 ____ _ _ 7 r___ 41 T _1 Downloaded from http://online.ucpress.edu/abt/article-pdf/56/1/51/46455/4449743.pdf by guest on 29 September 2021 8 10 x__ _ __ _ __ _ _ 11 _ 1 _ _ __ _ _ _ _ _ 12 _ _ _ _ _ X _ _ _ _ _ _ _ 14 1 X 1 _ I_I_I __ _ _ _ _ _ _ _ _ _ _ __ _ __ _ ___ __ _ 15 7__ 1 16 ______ 1 _ 1 7 1 _1_1 17 --- 18 _ -_ _ _ _ X _ _ _ _ _ _ 19 1 1 I . 1_1_._I___ 20 21 _ 22 23 T _ I _T___1_1_ 24 T_1 - _-- X T _______ 25 _ _ _ _ _ 26 X___ _ 27 __ _ _ 28 _ -- X _______ 29 _ T ----1 __T_1--_1_1 30 _ 7_ ____1____ 31 _ _ Xx I ______ 32 _ _ _ _ X _ r ___ __ 33 _ _ __________ 34 I T 1 _______r_ Figure 1. Sample data sheet for collecting data on the presence or absence of galls on individual stems of goldenrods. Students are instructed to place an X in the appropriatecolumn when a gall is present and leave all columns blank for a stem with no galls. 52 THEAMERICAN BIOLOGY TEACHER, VOLUME 56, NO. 1, JANUARY'1994 Table 1. Data from transects recording the number of goldenrod stems in each category. Ball & Ball & Bud & Study No Ball Bunch Ellipse Bud Bunch Bud Bunch Total Site Galls Gall Gall Gall Gall Galls Galls Galls Stems 1 698 2 128 1 1 0 0 0 830 2 337 3 14 0 2 0 0 0 356 3 312 11 77 1 6 1 1 2 411 A third species of gall-makeris Rho- ing insects on goldenrods tend to goldenrod? Or, would you expect to palomyiasolidaginis, a gall midge. This avoid each other, ignore each other, or find stems with only one kind of gall?" is one of several midges that produces attracteach other?As a group, discuss Similarly, "If the different species of different types of galls on goldenrods the ways one could answer this ques- gall insects attracted each other, (Felt 1940). Rhopalomyiasolidaginis pro- tion, including direct observations of would you expect to find stems with duces a rosette or bunch gall. In other ovipositing insects. The students then several kinds of galls?" Based on this words, leaves are bunched together at must try to find a way to answer this discussion, students realize they must the top of the plant, as if the stem question given the following con- survey goldenrod stems to find out failed to elongate but continued to straints: what kind and how many galls exist Downloaded from http://online.ucpress.edu/abt/article-pdf/56/1/51/46455/4449743.pdf by guest on 29 September 2021 on individual stems. produce new leaves. Little is known 1. The question should be answer- At the field site, the students are about the naturalhistory of this partic- able within the 3-hour time span ular insect. Hartnettand Abrahamson faced with two problems: 1. how to of one laboratoryperiod. (1979) found rosette galls to be rela- identify the goldenrod species and 2. If the time of year is fall or win- and 2. tively abundant in central Pennsylva- ter, only galls are available. galls, how to sample the stems. nia (0-3.97 gall/m2);and Maddox and Goldenrods are difficult to identify; Root (1987) indicate that Rhopalomyia Often, the students have a difficult they have tremendous variability in solidaginisis restricted to feeding on time with this task and might need to appearance within species. The in- Solidagospecies. be prompted with leading questions. structormust choose carefullythe field After the students have a back- For example, "If the different species site for the exercise.