MORGAN HEBARD 259 



SUPPLEMENT. ADVENTI\^E MATERIAL 



In the following pages are listed the Blattidae which, in various 

 ways, have been found to be adventive, but not established, in 

 portions of the United States and Canada. These represent 

 thirty-one species, of which eight are also native in southern por- 

 tions of the United States. One hundred and forty-one specimens 

 have been examined. 



It is clear that almost any exotic species may be carried alive by 

 commerce to this country, this being facile in the case of forms 

 which are domiciliary to various degrees. It is equally evident 

 that, unless particularly adapted to the environmental and 

 climatic conditions encountered, hardly any possibility exists of 

 their becoming permanently established. Thus, species from 

 Europe and other regions of temperate climate might easily be- 

 come firmly established. Species from the tropics, however, 

 could not survive in the United States, except possibly in the very 

 limited tropical areas on the southern border of this country, or 

 elsewhere under precarious artificial conditions. 



The enormous number of species which might be brought to 

 this country, without any likelihood of becoming established, is 

 illustrated by the observations made by the author on the fruit 

 steamer "Tenadores." After leaving New York with hold 

 empty, eight species of tropical Blattidae were secured ; of these four 

 only have been found adventive in United States. Of these four, 

 two are also apparently native in the southernmost regions of the 

 United States; none have been introduced and become established. 

 To treat fully each species which is recorded as adventive, but not 

 established, would in consequence be of little real value. The 

 systematic analysis would require a comparative discussion and 

 treatment of allied species which have no bearing whatever on the 

 species native in the United States. 



In the preparation of the present paper, we have made no effort 

 to discuss the adventive species, but careful comparisons have 

 been made with all of the related exotic species available, and the 

 literature has been studied for all of these, in order to insure as 

 nearly correct determinations as possible. 



MEM. AM. ENT. SOC. 2. 



