743 



Superfamily CHALCIDOIDEA 



By Gordon Gordh 



The Chalcidoidea are among the most difficult groups of Hymenoptera to identify because of 

 their small size and the lack of adequate keys to the North American species. Several species vie 

 for the distinction of being the smallest insect (about 0.2 mm long), and most species are less 

 than 3-4 mm long. The characters used to distinguish chalcidoids from other Hymenoptera in- 

 clude the presence of a prepectus, failure of the pronotum to meet the tegula, 13 or fewer seg- 

 ments comprising the geniculate antenna, and drastically reduced wing venation. 



Ashmead (1904) recognized 14 families and provided the first comprehensive modern classifi- 

 cation of the Chalcidoidea. Despite its many errors, this was a prodigious work and remarkable 

 considering the primitive optical equipment and state of knowledge about the Chalcidoidea at 

 that time. Nikol'skaya (1952) elevated the number of families to 24, and Boucek and Hoffer 

 (1957) (subsequently translated by Peck, 1964) recognized 18 families. In this catalog Burks has 

 reduced the number of families to eleven. Casual thought may lead one to wonder why there is 

 so much inconsistency among workers regarding higher classification of chalcidoids. These clas- 

 sifications are based on external morphology, and the chalcidoids are exceedingly plastic 

 morphologically. This plasticity generates differences of opinion over the limits of higher taxa 

 because workers weight characters differently. 



Chalcidoids are found in all zoogeographical regions, in all terrestrial habitats, and all families 

 are found in each zoogeographic region. Despite their omnipresence, chalcidoids remain one of 

 the poorest known superfamilies. Taxonomically, the western Palearctic fauna is best known, 

 followed by the Nearctic. The remainder of the zoogeographical regions (Neotropical, Ethiopian, 

 Australian, and Oriental) are almost completely unknown with respect to their endemic faunas. 

 Much of our knowledge of chalcidoids stems from species which are associated with agriculture. 



The body size and searching habits of chalcidoids make them suitable for fossilization in 

 resinous amber, but fossil records of the Chalcidoidea are incomplete. Fewer than 50 species are 

 known, and these belong to less than half of the chalcidoid families. The most comprehensive ac- 

 counts of fossil chalcidoids are by Brues (1910), Doutt (1973), and Yoshimoto (1975). The last 

 study provides a summary of knowledge about fossil chalcidoids. Yoshimoto (1975) reports that 

 mymarids, trichogrammatids, and tetracampids are referable to the Cretaceous Period (70-90 

 million years before present). 



Owing to the paucity of knowledge about fossil chalcidoids and their morphological plasticity, 

 the relationship of this superfamily to other parasitic Hymenoptera has not been conclusively 

 established. We are not certain that the Chalcidoidea are monophyletic in the Hennigian sense, 

 although some investigators have that opinion. An interpretation of chalcidoid phylogeny based 

 on the known fossil record is provided by Yoshimoto (1975). 



The actual numerical dimension of the Chalcidoidea can only be speculated. The ichneumonid 

 specialist Henry Townes (1969) has estimated that there are 60,00() species of Ichneumonidae. 



