BIOTIC ASSOCIATIONS OF COCKROACHES — ROTH & WILLIS 9I 



IV. CLASSIFICATION OF THE ASSOCIATIONS 



Asano (1937) classified the natural enemies of cockroaches into 

 two types as follows : 



1. Enemies that feed mainly on cockroaches (certain ripiphorid beetles and 



certain chalcid, evaniid, and ampulicid wasps). 



2. Organisms which, in their search for food, devour cockroaches that may be 



encountered (certain species of scorpions, spiders, ticks, centipedes, Strepsip- 

 tera, ants, birds, rats, and "parasitic bacteria"). 



Cameron (1955) arranged the associates of cockroaches in two 

 groups as follows : 



Group A. Parasites and predators. 



1. Parasites: Hymenoptera (Evaniidae, Eulophidae, Eupelmidae, Encyrtidae, 



Pteromalidae, Cleonymidae) and Coleoptera (Ripiphoridae). 



2. Predators: Hymenoptera (Ampulicidae), Hemiptera (Reduviidae), Coleop- 



tera (Dermcstidae), Arachnida (Araneae, Acarina). 



Group B. Parasites and symbionts. 



1. Protozoa (including examples of both parasites and commensals). 



2. Nematoda (including both primary "parasites" and secondary parasites). 



3. Bacteria (including the mutualistic bacteroids). 



4. Algae [Arthromitis (= Hygrocrocis) intestinalis; see p. 124]. 



Asano's arrangement, although essentially true, is limited; Cam- 

 eron's system is divided into arthropods (group A) and lower 

 forms (group B), but does not include higher animals. Both attempts 

 at classification need amplification ; this we have endeavored to do 

 below. 



In classifying the biotic associates of cockroaches, we were im- 

 mediately confronted with a problem in semantics. The concepts 

 parasitism, predatism, and symbiosis have all been used with various 

 shades of meaning by different authors. The problem is not solved 

 merely by accepting as authoritative specific definitions, however apt 

 they seem to be, because, unfortunately, these concepts are not mu- 

 tually exclusive. For example, among the entomophagous insects, as 

 Sweetman (1936) has pointed out, there can be no definite line of 

 separation between parasitism and predatism : the two intergrade, 

 only the extremes being quite distinct. In fact, Andrewartha and 

 Birch (1954) generalized these relationships by calling both cate- 

 gories predatism. These authors divided natural populations of 

 associated organisms into nonpredators and predators. Although this 

 simplifies their presentation of the general principles of ecology, for 

 our purpose more narrowly defined terms have proved useful. 



In the main we have followed Sweetman (1936) and Allee et al. 

 (1949) in arriving at the following definitions: 



