Golden Rod Gall Fly Research Paper

A Eurosta solidaginis, also known as the Golden Rod Gall Fly, is an insect that lives in a Solidago atlissma/ canadis. The female Gall Fly has an ovipositor which implants eggs in the Golden Rod plant. Eggs are implanted by the mother onto the apical meristem. At the apical meristem the larva releases a chemical that stimulates the host goldenrod which in return forms the gall (Abrahamson, Kenneth, McCrea, Whitwell, and Vernieri 1991). The gall acts as a protective barrier for the Eurosta Solidagnis. The larva transforms from larvae to pupa in the gall. The Eurosta solidaginis predators include other insects and birds. The ovipositon, which is the placing of the eggs, occurs in mid- late May (Abrahamson, Sattler, McCrea, and Weis 1989). The gall start to appear about 3 weeks after the oviposition, and they finish growing, reaching their full size three to four weeks later. The
larva enters a diapause in late September and later in the year around March or April the gall fly larva pupates (Abrahamson et al. 1989). The Galls provide protection for the larva against non-specialized predators. However these galls are still not enemy free. The Eurosta solidaginis is not the only organism that emerged from the Golden Rod gall. Three other organisms were also emerged from the galls. Cane and Kurczewski (1976) found that two types of Eurytoma and one type of Mordellista inhabit the galls. These three organisms are known as some of nature’s specialized predators toward the gall fly (Stone and Schonrogge 2003). The three insects are not the only predators of the gall fly. Birds also prey on this small animal. The two types of Eurytoma were the Eurytoma giantea and Eurytoma obtusiventris, which are both parasitoid wasp.
The Eurytoma Gigantea is an external parasite. The Eurytoma gigantea attacks after the gall has reached its full size. The wasp remains in the central chamber of the gall after consuming the larva in mid-August. While in the gall this wasp feeds on the plant matter (Abrahamson et al. 1989). The Female Eurytoma giantea is technically a different parasitoid. The female wasps inject eggs into to the gall when the gall is thinner than the length of the parasitoid. This parasitoid is limited to smaller galls. The other type of Eurytoma is the Eurytoma obtusiventris. The Eurytoma are an internal parasite most prevalent during the hatching of the gall maker’s eggs during the time when the eggs hatch and the larva bore through the stem. When the Eurytoma obtusiventris attacks the larva, it causes the larva to prematurely pupate, and then the parasitoid consumes the gall fly. The Eurytoma obtusiventris remains in the gall throughout the winter until it pupates in the spring (Malcom
nd). One of the other specialized predators is a beetle
Stone and Schononrogge 2003). The specific beetle was the Mordellistena unicolor. The Mordellistena unicolor eats the gall tissues by chewing narrow channels through the gall’s parenchyma and vascular regions. The larva that hatch early July and bore into the gall tissue by early august. Although the Mordellistena unicolor is considered to be an animal that lives in a burrow it usually ends up eating the gall fly (Abrahamson et al. 1989). The galls were not only targeted by parasitoid wasp and beetles the galls were also attack by birds. The two birds that mostly attack the Eurosta solidagnis were the downy wood pecker and the black-capped chickadee. The amount of bird predation vary from site to site (Abrahamson et al. 1989). It was found by many scientists that the gall size has a direct relationship with the type and amount of predation that came toward the gall fly. Cane and Kurczewski (1976) found the amount of mortality factors of the population of the Eurosta solidagnis and how much of an influence each mortality factor had. In nearly 28% of all galls, Cane and Kurczewski (1976) found had untouched gall fly larva. The other 72% of the galls had been touch by other factors. About 20% of the galls showed signs of bird predation, 23% were entered by Eurytoma obtusiventris, 11% of the galls were affected by the Eurytoma gigantea, the Mordellistena only affected 1% of total galls, and the last 17% was affected by unknown factors. Other scientists found similar results but they also found that the percentage varies based on gall size. All of the predators had different preferences on gall size because of particular reasons. Abrahamson, Sattler, McCrea and Weis (1989) found that birds were more probable to attack larger galls. The probability of galls being altered by birds ultimately decreased as the gall diameter decreased (Cane and Kurczewski 1976). The Eurytoma gigantea was also inconsistent with the percentages. Abrahamson, Sattler, McCrea and Weis (1989) found that the Eurytoma gigantea was restricted to galls of a particular size range while the other parasitoid enemies do not have this restriction such as the Eurytoma obtusiventris. When tested the diameter of the galls in which these two organisms were found constantly varied. This data shows that the E. obtusiventris and M. unicolor have no restrictions regarding gall size. Interactions between gall flies and the predators of the Eurosta solidaginis are very complex, and the gall size does affect the predators that prey on the gall. Lastly we will not be using the same method of data collection as other scientist (Abrahamson et al. 1989). We will also be looking at how the gall properties effect the type of predator that preys on the galls. There are some major differences between what we are doing and what these scientists did, For starters we will not be using the same location for gall collection. Also we will not be measuring the bird predation like Cane and Kurczewski (1976). Lastly we will not be using the same method of data collection as other scientist (Abrahamson et al. 1989).

References:
Abrahamson WG, Sattler JF, McCrea KD, Weis AE (1989) Variation in selection pressures on the goldenrod gall fly and the competitive interactions of its natural enemies. Oecologia 79: 15-22

Abrahamson WG, McCrea KD, Whitewell AJ, Vernieri LA (1991) The role of phenolic in goldenrod ball gall resistance and formation. Biochemical Systematics and Ecology Vol. 19:615-622

Cane JH, Kurczewski FE (1976) Mortality Factors Affecting Eurosta solidagnis (Diptera: Tephritidae). Journal of the New York Entomological Society Vol. 84: 275-282

Malcom S (nd) analysis of herbivory and natural enemy attacks through 3 trophic levels. Dept. Biogical Sciences, WMU.

Stone GN, Schonrogge K (2003) The adaptive significance of insect gall morphology. Trends in Ecology and Evolution Vol. 18: 512 to 522