744 Hymenoptera in America North of Mexico 



DeBach (1974) has estimated that somewhere between 70-90 percent of the parasitic Hymenop- 

 tera remain to be described. I believe that the Chalcidoidea wiir ultimately be recognized as 

 larger than the Ichneumonidae. There are some who would disagree with this estimate, but their 

 estimates are based on impressions developed from examining species that repeatedly have 

 been submitted for identification. These species mostly are associated with the agroecosystem 

 and represent only a portion of the total chalcidoid fauna. My primary interest in making these 

 assertions is to stimulate research on the Chalcidoidea because they are a fertile area for in- 

 vestigations in biology, behavior, ecology, and systematics. 



Chalcidoids have diverse and frequently specialized feeding habits. Most species of chalcidoids 

 are parasitic, but phytophagy probably has evolved several times in the Chalcidoidea because it 

 is found in several distantly related taxa and many unrelated species of plants serve as hosts. 

 Phytophagy is found most frequently in association with gall-forming habits, but the evolutiona- 

 ry significance of this observation remains unknown. 



Agaonids demonstrate the most intimate expression of phytophagy in the Chalcidoidea. This 

 group is poorly represented in North America because all agaonids develop in fig seeds (Ficus 

 spp.), and these plants occur naturally only in tropical and subtropical climates. All figs are de- 

 pendent on agaonids for pollination, and agaonids can only develop within the receptacles of 

 Ficus. Host specificity seems to be the trend in agaonids with each species of fig having its own 

 agaonid for pollination (Ramirez, 1970 a,b; Grandi, 1961). Numerous other chalcidoids are as- 

 sociated with Ficus as inquilines (Hill, 1967 a,b). 



Other taxa of chalcidoids with phytophagous species include the Eurytomidae, Torymidae, 

 brachyscelidiphagine Pteromalidae, and Tanaostigmatidae. 



Some ecologists prefer to use the term parasitoid to characterize parasitic insects. Protelean 

 parasite is a phrase often used to distinguish between typical parasites and insects that are 

 parasitic in the larval stage only (Askew, 1971). 



One definition of parasitism for all parasitic organisms is impractical because animal species 

 are parasitic in many different ways. The parasitological definition of parasitism in the sense of 

 parasitic worms and protozoa is unsuitable in the present context because parasitic chalcidoids 

 do not behave in a manner consistent with that definition. Therefore it seems more appropriate 

 to list some of the biological attributes of parasitic chalcidoids. Parasitic chalcidoids are charac- 

 terized as follows: (1) they are obligate parasites in the larval stage only; (2) they require only 

 one host to complete development; (3) they attack related taxa (other arthropods and usually in- 

 sects); (4) if the parasite completes development, the host invariably dies; (5) the ratio of size 

 between the parasite and host approximates unity (except in some cases where the parasitic lar- 

 vae are gregarious or polyembryonic delevopment occurs). 



Adults of some species host feed, but the significance of this behavior is not always clear. 

 Host feeding may provide nutrients necessary for ovary or egg development, or it may be a con- 

 venient source of nutrients necessary for sustaining life (Flanders, 1953; Doutt, 1964; Quezada et 

 ai, 1973). 



Parasitism by insects reaches its most elaborate development in the Chalcidoidea. Primary 

 parasitism (larval development on a phytophagous host) is the most common type of parasitism 

 by chalcidoids. Hyperaparasitism (a parasite attacking another species of parasite) is found al- 

 most exclusively in the Hymenoptera, and reaches its most extensive development in the Chalci- 

 doidea as indicated by the fact that most families have hyperparasitic species. Further evidence 

 of the extensiveness of hyperparasitism in this superfamily is found in the fact that several 

 types of hyperparasitism have evolved in the group. These include secondary (a parasite at- 

 tacking a primary parasite), tertiary (a parasite attacking a secondary parasite) and quaternary 

 (a parasite attacking a tertiary parasite). Hyperparasitism probably evolves out of primary 

 parasitism in situations involving strong interspecific competition. 



An unusual type of hyperparasitism occurs in Coccopkagoides utilis Doutt and various related 

 genera such as Coccophagus, Eyicarsia, and Prospaltella. Female larvae develop as primary 

 parasites of armored-scale insects, and the male larvae develop as hyperparasites of their own 

 females (Broodryk and Doutt, 1966). This phenomenon is called adelphoparasitism or au- 

 toparasitism and appears restricted to the aphelinines (Zinna, 1961; Flanders, 1959, 1967). 



Parasitic chalcidoids can be categorized on the basis of where the egg is deposited and how 

 the larva feeds. Most species attack the host directly, but adult female eucharitids and perilam- 

 pine pteromalids oviposit on vegetation and the first-instar larva (planidium) searches for the 

 host (Smith, 1912; Clausen, 1940 a,b). Species in which the adult female directly attacks the host 





