GRASSHOPPERS IN RELATION TO PLANT ASSOCIATIONS. 165 



in place, in surroundings, may Make certain species appear more 

 or less abundant or frequent than they really are. 



The method used by Shull ('n : 218) in estimating numbers of 

 grasshoppers per unit of area is valuable, but does not distinguish 

 the different species. His suggestion "to collect immense num- 

 bers, and depend upon majorities to decide the usual habitat," 

 besides being impracticable, is not satisfactory, for the numbers 

 collected are not a true index of the numbers which actually occur 

 by reason of the difficulties mentioned above. 



The Method Used in Determining Frequency and Abundance 

 The method used by the writer was to visit the various habitats, 

 taking one or several grasshopper specimens of each species for 

 verification, and to estimate abundance not from the numbers 

 collected, but from the numbers observed per unit of area in each 

 station, having in mind the considerations which tend to over- or 

 underestimation of actual numbers. 1 If in the bracken-blue- 

 berry growth, a considerable number of Melanoplus angustipennis 

 could be seen nearby, within a rod or two, and if this condition 

 was practically uniform over the area of the association, as nearly 

 as could be seen, an infinity sign was put down in the field notes 

 opposite its name, indicating numbers in which it occurred, 

 followed by the number collected, thus (oo, 2). If in twenty 

 minutes walk through the aspens only four or five specimens of 

 Scirtetica marmorata were seen, and two collected, the notes 

 would appear thus (s, 2), the letter s representing several. If in a 

 half-mile of sandy roadway, a considerable number of specimens 

 of Spharagemon were seen, but never close enough together to be 

 abundant, the numbers w r ould be indicated by the plus sign 

 (-f , i). If a species was taken in a particular kind of habitat 

 in nearly all stations of this habitat visited, or if it was regularly 



1 Facilities for determination were available at the biological station, and the 

 species were identified as they were taken. With most of the species the writer 

 had been acquainted, and the species soon became so familiar as to be recognizable 

 at sight. In life there are many rather conspicuous peculiarities of color and of 

 behavior which aid in recognition. Whenever there was doubt as to identity, as 

 in the case of Melanopli particularly, specimens were caught and examined critically 

 in the field, to avoid overlooking species of similar appearance. In all cases one 

 or several specimens of each species were kept for verification. There is no reason 

 why many familiar insects should not be recognized at sight as easily as birds are 

 identified by ornithologists. 



