BIOTIC ASSOCIATIONS OF COCKROACHES — ROTH & WILLIS I9I 



cockroaches were infected with both of the above species of nema- 

 todes. The average number of both species was 7.5, and the maximum 

 number was 97; the mean number of H. diesingi was 5.1 and the 

 maximum 64; the mean number of L. appendiculata was 2.4 and the 

 maximum 33. More than 40 nematodes were found in each cockroach 

 of 1.3 percent of those examined. These results apparently contradict 

 Caleb's conclusions inasmuch as the number of each species in mixed 

 infections was essentially the same as the number found in cock- 

 roaches infected by only one species (see pp. 195 and 197). Dobrov- 

 olny and Ackert (1934) found that 29 percent of 222 Periplaneta 

 americana contained both of the above species of nematodes ; whereas 

 40 percent contained L. appendiculata only, and 21 percent contained 

 H. diesingi only. The infestation ranged from i to 36 worms per cock- 

 roach with averages of 3.8 per male, 5.1 per female, and 2.7 per 

 nymph. 



The eggs of some helminths pass unharmed through the guts of 

 cockroaches that serve as vectors of these ova and have no effect on 

 the insect. However, helminths that are secondary parasites in cock- 

 roaches damage the insect to varying degrees depending upon the ex- 

 tent of the infection. Thus the larvae of Moniliformis moniliformis 

 pass through the gut wall and some may become embedded in the fat 

 tissue (Moore, 1946). First stage larvae of Oxyspirura mansoni also 

 burrow through the midgut wall into the fat body; Sanders (1929) 

 believed that Pycnoscehis siirinamensis could be killed if at one time 

 a sufficient number of migrating larvae of O. mansoni penetrated the 

 cockroach's intestinal wall. Gongylonema neoplasticum migrates 

 through the digestive tract and encysts in the muscles of the thorax 

 and legs of the host (Fibiger and Ditlevsen, 1914). Infective larvae 

 of Protospirnra muricola, after hatching from ingested eggs, pass 

 through the cockroach's gut wall and encyst mainly in the thorax, 

 around the crop, and at the bases of the large muscles of the pro- 

 thoracic legs (Foster and Johnson, 1939). It is probably generally 

 true that nematodes which are secondary parasites in cockroaches do 

 some damage to the host's intestinal tract at least, and they probably 

 also damage other organs in which they may encyst. 



Cockroach tissues may react defensively to infections by parasitic 

 nematodes. For example, encysted third-stage larvae of Physaloptera 

 turgida have been found enclosed in a thin, brown, chitinous substance 

 that was undoubtedly deposited by the tissue of the cockroach (Ali- 

 cata, 1937). Cysts of similar appearance have been found in cock- 

 roaches infected with Physaloptera vara, P. maxillaris, P. hispida 

 (Petri, 1950; Hobmaier, 1941 ; Schell, 1952), and Gongylonema 



