Acrididae 289 



II. Choice oj a Species. The following points should be considered 

 in selecting a species for laboratory culture if the problem does not 

 necessitate the use of a particular species: (1) hardiness, (2) availabil- 

 ity, (3) availability of natural food plants, (4) number of generations 

 per year and size of broods. Let us briefly consider these points. 



1) Hardiness and 2) availability. Usually indigenous species are 

 preferable since change of climate and altitude are thus eliminated. The 

 shift from freedom to captivity is severe under the best conditions. 

 Correlated with the above advantages are natural conditions for their 

 food plants. I have no doubt that hardy species may be found in every 

 locality. In general, tryxalines are the most delicate, oedipodines 

 intermediate, and acridines the most vigorous, but as a group the latter 

 are the most restricted as to their food plants. However, many species 

 of Melanoplus in addition to being extremely hardy are almost om- 

 nivorous so far as plants are concerned. M. dijjerentialis in particular 

 on account of its wide distribution and large size is very favorable for 

 general laboratory purposes. M. bivitatta in its range would be equally 

 satisfactory. Romalea microptera, a large, almost flightless acridine 

 from the south thrives in captivity and may be purchased from collectors. 

 Owing to its size the provision of food and space becomes a problem if it 

 is necessary to keep large numbers on hand. Dactylotum pictum is 

 another acridine which does well in captivity, perhaps because of its 

 wingless condition. 



Most oedipodines are strong flyers and perhaps for that reason do not 

 thrive in captivity. Notable exceptions exist, however. Encoptolophus 

 subgracilis taken from Tuscon, Ariz., to Philadelphia, proved to be the 

 most satisfactory grasshopper I have ever raised so far as ease of culture 

 is concerned. It is hardy and produces a generation in six weeks. Chor- 

 tophaga australior, also a southern form, is nearly as favorable. More 

 northern species of these genera normally hibernate over the winter, 

 E. sordidus in the egg and C. viridijasciata in the nymph stage. Both 

 will complete their development without a pronounced pause if kept at 

 2 2°-25° C. Trimerotropis maritima and T. vinculata are satisfactory 

 but will produce normally only one generation per year. 



The tryxaline, Chloealtis conspersa, is a notable exception to the rule. 

 It is very hardy and conveniently lays its eggs in old, somewhat rotten 

 wood, preferably fallen branches of trees. The eggs are laid in August 

 and September and normally hatch in the spring. 



All of the species mentioned are known to be sufficiently hardy to 

 make good laboratory stock. But no one should be deterred from trying 

 out other species, especially if they are indigenous so that the stock may 

 be replenished from nature. 



3) Availability of natural food plants. As has been stated, many 



