350 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



Biologists or other interested people have sometimes imported eggs 

 of exotic species, in order to observe the growth of these unusual 

 insects in cages, and the species have been intentionally or accidentally 

 released. Of course, each species is suited to certain weather condi- 

 tions, and it usually will not survive if released in an area that is 

 radically different from its native home in temperature, rainfall, 

 humidity, or other basic climatic factor. In the case of the two 

 Oriental and one European species introduced into the northeastern 

 United States, the climate of certain areas has enabled them to mul- 

 tiply and become thoroughly established. Their spread in the United 

 States is limited to what is possible by natural methods, aided by the 

 movement of eggs or individual specimens on the part of people, and 

 doubtless will not extend into States where winters are too severe, 

 where desert conditions prevail, or where for other reasons the situa- 

 tion is not suitable. 



Many insects introduced into the United States have not been so 

 interesting or so harmless as the mantids here discussed. The Jap- 

 anese beetle, European corn borer, gypsy moth, San Jose scale, and 

 Oriental fruit moth are only a few of the outstanding pests that have 

 reached us from abroad and that have cost the Nation almost untold 

 expense for control work, to say nothing of personal hardship brought 

 about by accompanying adjustments in agricultural practices or 

 market conditions. 



OVERWINTERING 



In temperate regions mantids pass the winter in the egg stage, the 

 adults all dying in fall and the new generation hatching the follow- 

 ing spring or early in summer. Egg masses are much more noticeable 

 during winter, because at other times they are likely to be concealed 

 by leaves or other green vegetation. In some northeastern or Atlantic 

 Coastal Plain States as many as 50 egg masses may be found in less 

 than an hour in particularly favorable localities. 



In warm countries with no winter season there may be a resting 

 period or diapause in the life cycles of mantids. This is frequently 

 correlated with dry and rainy seasons. Some desert mantids pass the 

 diapause as nymphs. For instance. Iris deserti Uvarov, of Algeria 

 and Tunisia, usually spends the diapause, which lasts 4 to 5 months, 

 in the fifth nymphal stage. 



ENEMIES 



There is a high mortality among young mantids during the first few 

 days following hatching, when they are delicate and only small insects 

 can be captured. Hard, cold rains at this time may inflict a heavy 

 toll, and birds may eat large numbers. 



To determine which birds and mammals feed on mantids or their 

 egg masses, I consulted the Food Habits Division of the United States 



