GRASSHOPPER GLACIER OF MONTANA — GURNEY 315 



search for population build-ups and incipient outbreaks on a much 

 more scientific basis than formerly. Aggregations of a species ca- 

 pable of undergoing phase transformation may be sampled and from 

 the appearance of the individuals it can be determined whether they 

 belong to the phase which typically is of minor importance (solitary 

 phase), or whether in wing length and other characteristics there is 

 a trend toward the typically long-winged and highly destructive mi- 

 gratory condition in which the individuals gather in compact swarms 

 (gregarious phase) . While the phase characteristics of samples are 

 sometimes clear by simple inspection of specimens, in other cases it 

 is necessary to measure parts of the body in order to obtain certain 

 ratios which are valuable clues to phase change. The ratio most often 

 used is that obtained by dividing the length of the front wing (called 

 the elytron, or tegmen) by the length of the hind femur; hence the 

 abbreviation, E/F ratio. With different migratory species the ratio 

 that is most sensitive to phase changes, and thus most dependable as 

 an indicator of phase condition , varies. For instance, it has recently 

 been learned that a ratio utilizing the width of the grasshopper's head 

 at the broadest expanse of the cheeks is very useful for identifying 

 the phase of Schistocerca gregaria, the desert locust of North Africa 

 and western Asia. 



Now to return to the samples of Melanoplus ?nexicanus mexicanus 

 from the solid ice of Grasshopper Glacier. They were first identified 

 as M. spretus by Caudell who at the time did not have the benefit of 

 modern studies by Faure (1933) and Brett (1947), which indicate 

 the synonymy of spretus. The specimens I have seen are rather long- 

 winged individuals suggestive of the gregarious phase, but they are 

 too broken to permit complete measurements to be made. Further- 

 more, the samples include too few specimens for a reliable conclusion. 

 When Dr. Parker visited the glacier in 1931 he noticed in particular 

 the red hind tibiae of specimens uncovered by the melting ice. This 

 agreed with the gregarious phase, though it did not rule out the soli- 

 tary phase. When sufficiently large and perfect samples are obtained 

 from the ice a statistical study of the E/F ratio may of itself be very 

 suggestive of the correct biological nature of the specimens in the 

 older preserved layers. If their age is also determined by the carbon- 

 14 test or other means, we will then have information on the phase 

 character of this highly important grasshopper for a known period 

 in its past history, the doors to which are now entirely closed to us. 



their tendencies to migrate. The possibilities for confusion are still further increased 

 by the habit, among the general public in the United States, of calling cicadas "locusts." 

 These insects, of which the periodical cicada or "17-year locust" is best known, belong 

 to a quite unrelated group. For the sake of clarity, North American entomologists now 

 tend to avoid the use of "locust" except when referring to foreign species of grasshoppers 

 for which the term has clearly been established. 



