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A STUDY IN HYPERPARASITISM 9) 
species, which has been referred to in literature (19) under the name of 
Pteromalus egregius Foerst., usually parasitizes cocoons of Apanteles 
and Meteorus, but is sometimes found living as a primary parasite of 
the brown-tail moth larvae, and recently it has been observed attack- 
ing hibernating larvae of the satin moth (Stilpnotia salicis L.). And 
species of Hemiteles and Gelis, ichneumonids that are notorious ene- 
mies of hymenopterous primary parasites, are themselves sometimes | 
primary, attacking spider egg masses and such lepidopterous hosts 
as Coleophora and Bucculatrix, the cases or cocoons of which closely 
resemble the cocoons of hymenopterous parasites. Cases where 
primary parasites acted as secondaries have been observed even more 
frequently. Often they are accidentally secondary as a conse- 
quence of attacking hosts within which other parasites are already 
present. This occurs commonly in the case of the boll-weevil par- 
asites Cerambycobius cyaniceps Ashm., Eurytoma tylodermatis Ashm., 
and Microdontomerus anthonomi Crawf., according to Pierce (30). 
It has been noted with parasites of scale insects, such as Coccopha- 
gus and Tomocera (85); with Galesus silvestri Kief., a serphoid 
parasite of the Mediterranean fruit fly (28); with Theronia fulves- 
cens Cress., an icheumonid that attacks various lepidopterous larvae 
(11), and with numerous other species. It appears to be generally 
true that hyperparasitism of this accidental type becomes increas- 
ingly abundant with the increase in actual numbers of the various 
primary parasites of certain hosts. It should not be confused with 
true competitive parasitism, where different species of primary 
parasites compete for the limited food supplied by a single host, 
one causing the death of the other only indirectly, by first appro- 
priating the available food. Manifestly competitive parasitism 
also becomes of more frequent occurrence as the numbers of the 
various primary parasites of a given host increase, and because 
of the difficulty of observation it is often confused with accidental 
secondary parasitism.- Sometimes primary parasites become direct 
secondary parasites and are not merely accidentally so because of 
the earlier presence of another parasitic species. Thus certain 
species of the eupelmid genus Anastatus, which are regarded as 
strictly primary parasites of the eggs of Lepidoptera, Orthoptera, 
etc., and are usually much restricted as to hosts, successfully attack 
the cocoons of other primary parasites, particularly Braconidae. A 
similar habit has been observed in the case of various other chal- 
cids, and also with some ichneumonids. At least four such species 
were encountered among the parasites of Apanteles melanoscelus, 
and will be briefly treated later. 
Following the general rule stated by Howard (1/4) for primary 
parasites—namely, that they are external feeders when parasitic upon 
protected hosts, and internal when attacking exposed hosts—most 
hyperparasites that attack primary larvae which are protected by 
their cocoons are external feeders, whereas those that parasitize 
primaries like the eulophids Comedo, Euplectrus, and Elachertus, 
which form naked exposed pupae, are usually internal. Since rela- 
tively very few primary parasites are not protected either within 
cocoons or puparia, the number of internal feeders among secondaries 
is correspondingly small, the reverse of the condition found with 
primaries. ) 
