6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I4I 



among all other insects. Secretions produced by certain cockroaches 

 (e.g., 2-hexenal by Eurycotis floridana) will ward off certain predators. 

 The identities and biological activities of most cockroach secretions 

 are unknown, but the use of protective chemicals against predators 

 may be widespread among cockroaches. If so, how effective are these 

 repellents in protecting the individual or the species ? It is not known 

 whether cockroaches are protected by apparent mimetic resemblances 

 to other arthropods. There is no experimental proof that insect para- 

 sites can successfully attack the eggs of cockroaches that incubate 

 their eggs while they are being carried by the female. 



It is conceivable that biological control of cockroaches might be 

 achieved in limited areas such as man-made structures or sewers, but 

 this possibility has not been thoroughly explored. It would be informa- 

 tive to know what effects, if any, organisms such as bacteria. Protozoa 

 (e.g., gregarines), intestinal nematodes, or other helminths have on 

 cockroaches. Possibly pathogenic microorganisms can be used for 

 biological control of cockroaches ; this approach seems to have been 

 little explored. 



Associations of colonial cockroaches (e.g., Cryptocercus spp.) may 

 be truly familial or they may merely result from gregariousness. 

 Newly hatched nymphs of species that carry their oothecae until the 

 eggs hatch cluster near the mother. This may be a response to the 

 mother as such, a search for shelter beneath the nearest object (thig- 

 motaxis? or negative phototaxis?), or there may well be yet another 

 explanation. Tepper in 1893 stated that the native cockroaches of 

 Australia are almost wholly carnivorous ; little supporting evidence for 

 this claim has been brought forward since that time. The apparent 

 supersedure of one species of domiciliary cockroach by another may 

 result from antagonism between different species, or it may result 

 from more rapid breeding and more effective utilization of available 

 food and space; but which? Several species of cockroaches are fre- 

 quently found associated with certain plants (e.g., bromeliads and 

 bananas) ; the ecological relations in these associations remain to be 

 determined. Many of the obscure associations between cockroaches 

 and other insects, spiders, birds, and burrowing animals have never 

 been adequately defined. The factors influencing cannibalism have 

 never been thoroughly investigated experimentally. These are only 

 a few ideas for future work that have occurred to us during the 

 preparation of this review. We hope that these suggestions as well 

 as other questions that may occur to readers will stimulate further 

 research in areas where it is obviously needed. 



