Some root galls from Cattleya sp. (left) and Laelia sp. (right)
Purpose:
This page is designed to illuminate an interesting family of Hymenoptera that is associated with root galls formed by insects on Araceae and Orchidaceae or as phytophages on Orchidaceae.
What:
Galls on the aerial roots of members of the Araceae (Philodendron, Dieffenbachia), Bromeliaceae (Tillandsia) and Orchidaceae (Cattleya, Laelia, Oncidium, Trichopilia, etc.) are spherical to elongate in form and range from 5mm – 20mm+ in size. One of the causes of aerial root galls, according to Gagné (1994), is certain species of gall midges (Diptera: Cecidomyiidae) as follows: Clinodiplosis cattleyae and Neolasioptera sp. (on Orchidaceae), an unidentified cecidomyiid in the tribe Oligotrophini (on Araceae: Dieffenbachia), and an unidentified cecidomyiid (on Araceae: Philodendron).
There exists a complement of parasitoids and potential phytophages which utilize these aerial root swellings during their life cycles. This page focuses on species of Eurytomidae in the subfamilies Rileyinae and Eurytominae. Specifically, a group of several species of Rileya and two other genera in Eurytominae (Foutsia, Aranedra) which are known exclusively from aerial root galls, while species of Aximogastra and Eurytoma orchidearum (Westwood) are known/suspected phytophages on orchids (See below).
Some root gall associates...
| Foutsia philodendri Burks | Aranedra millsi Burks |
| Aranedra arae Burks | Rileya new species |
To further explore those eurytomids associated with orchids, information is here presented on Eurytoma orchidearum (Westwood) which has been found feeding in the buds and pseudobulbs of various species of Cattleya, Laelia, Epidendrum, Brassavola, and Cypripedium (Orchidaceae) (Swezey, 1945; Tanada, 1953; Noyes, 1998). Also, species in the genus Aximogastra have been implicated as being phytophagous on Orchidaceae (see below).
More root gall associates...
| Amixogastra species | Eurytoma orchidearum (Westwood) |
Where:
So far as is known, all of these root gallers and their associates are found strictly in the New World, primarily Central and South America, but possibly extending into the southern United States.
Taxa:
Aranedra. This genus is represented by two species known from Central America, both described from Costa Rica, although two paratypes from Ecuador of A. millsi Burks are in the USNM collection. There are at least 1-2 undescribed species known from South America. Biology: Both nominal species are reared from root galls on Araceae: A. millsi from Philodendron and Dieffenbachia and A. arae Burks from Philodendron (Burks, 1971). The stem gall may be formed by Cecidomyiidae as Gagné (1994) records 7 species in at least 3 genera attacking stems of Piper spp. in the Neotropics.
Aximogastra.The type species was described from Brazil and another from the Caribbean (DeSantis, 1979). There apparently are several undescribed species from Costa Rica (Hanson, 1995). Biology: Originally described as "reared from orchids", other label data suggest these taxa are phytophagous in pseudobulbs of Laelia and Cattleya as well as being associated with Philodendron canes in quarantine.
Foutsia. This monotypic genus described by Burks (1971) is known from Mexico. This species may just be an unusual Sycophila as the characters Burks gave to differentiate the two were differences in the length of the petiole and that the gaster is more laterally flattened, both of which vary within Sycophila. Careful examination of this species and the range of variation across Sycophila is necessary to determine their relationship. Biology: possibly phytophagous in swollen roots of Philodendron (Araceae); however, Gagné (1994) records an unknown member of the tribe Oligotrophini (Cecidomyiidae) as forming galls on aerial roots of this genus of plant.
Rileya. There are approximately 31 nominal species, (excluding new synonymies, and new species (Gates, Ph.D. dissertation, 2000; publication in prep.)). Biology: all are parasitoids of Cecidomyiidae, where biologies are known. Several new species of Rileya are known only from root galls on Orchidaceae and Araceae and I suspect that similar or conspecifics will ultimately be reared from swollen aerial roots on Tillandsia (Bromeliaceae) caused by Neolasioptera sp. (Cecidomyiidae). However, one species described by Gomes (1943), Calorileya (=Rileya) nigra as "…de galhas em orquídea" (p. 245) has been implicated as the causative agent of orchid root galls (Lepage & Figueiredo 1947; Kraus & Tanoue 1999). Although oviposition by R. nigra was apparently observed (former reference), definitive proof is not provided as to whether or not this actually CAUSES the gall or if the wasp is parasitizing an early instar larva of Cecidomyiidae (see Hawkins & Goeden 1984).
| Tillandsia sp. root gall with emergence holes | Tillandsia sp. root gall | Neolasioptera sp. gall midge associated with root galls |
Wanted!!!:
Have you seen me? I am very interested in speaking to anyone who has reared or is rearing insects associated with aerial root galls. I am hoping to acquire specimens that have been preserved in 95% ethanol and have their associated galls preserved as well. Please feel free to contact me or to visit my other web pages!
Literature Cited:
Burks, B.D. 1971. A synopsis of the genera of the family Eurytomidae (Hym., Chalcidoidea). Transactions of the American Entomological Society 97(1):1-89.
De Santis, L. 1979. Catálogo de los himénopteros calcidoideos de américa al sur de los estados unidos. Publicación Especial Comisión de Investigaciones Cientificas Provincia de Buenos Aires, 488pp.
Gagné, R. 1994. The gall midges of the Neotropical region. pp. 352, Cornell University Press.
Hanson, P. 1995. 11.9 Eurytomidae, pp. 336-342. In Hanson, P. & I. Gauld [eds.]. The Hymenoptera of Costa Rica. Oxford Press.
Hawkins, B. & R. Goeden 1984. Organization of a parasitoid community associated with a complex of galls on Atriplex spp. in southern California. Ecological Entomology 9: 271-292.
Lepage, H. and E. Figueiredo. 1947. As Pragas das Orchidáceas. Instituto Biologico de São Paulo, São Paulo, Brazil.
Kraus, J. & M. Tanoue. 1999. Morpho-ontogenetic aspects of entomogenous galls in roots of Cattleya guttata (Orchidaceae). Lindleyana 14: 204-213.
Noyes, J. 1998. Catalogue of the Chalcidoidea of the world. CD-ROM. Expert Center for Taxonomic Information, Amsterdam, The Netherlands.
Swezey, O. 1945. Insects associated with orchids. Proceedings of the Hawaiian Entomological Society 12: 343-403.
Tanada, Y. 1953. The Cattleyafly, Eurytoma orchidearum (Westwood), in Hawaii. Hawaii Orchid Society Bulletin 5: 41-47.