1898] NOTES AND COMMENTS 9 



investigations will be made in that region where the cold currents 

 of the Antarctic and the warm Indian currents meet. The expe- 

 dition will then cruise through the Indian Ocean and the Red Sea, 

 reaching home after an absence which is estimated at nine months. 



We are able to add that the leader will be Professor Chun, 

 •director of the Zoological Institute of Breslau. The success of the 

 expedition, if started, will therefore be assured. 



The Cricket as Thermometer 



The American Naturalist, despite its change of editors, shows no 

 falling off in vigour. The November number contains a novel 

 observation by Mr A. E. Dolbear, and since his note is only a little 

 one, we venture to steal it whole : — 



" An individual cricket chirps with no great regularity when by 

 himself and the chirping is intermittent, especially in the daytime. 

 At night when great numbers are chirping the regularity is astonish- 

 ing, for one may hear all the crickets in a field chirping synchronously, 

 keeping time as if led by the wand of a conductor. When the 

 numbers are so great, the resting spells of individuals are unnoticed, 

 but when the latter recommence they not only assume the same 

 rate but the same beat as the rest in that field. The crickets in an 

 adjoining field will have the same rate, that is, will make the same 

 number of chirps per minute, but with a different beat, as one may 

 easily perceive by listening. 



" The rate of chirp seems to be entirely determined by the 

 temperature, and this to such a degree that one may easily compute 

 the temperature when the number of chirps per minute is known. 



" Thus at 60° F. the rate is 80 per minute. 



" At 70° F. the rate is 120 a minute, a change of four chirps a 

 minute for each change of one degree. Below a temperature of 50° 

 the cricket has no energy to waste in music and there would be but 

 40 chirps per minute. 



" One may express this relation between temperature and chirp 

 rate thus : 



" Let T stand for temperature, and N the rate per minute. 



4 

 " For example. What is the temperature when the concert of 

 crickets is 1 per minute ? 



4 



This is an observation suggestive of further inquiry. First, we 



should like to know whether it applies to all kinds of chirping or 



stridulating insects. And incidentally we may ask — what is the 



species, or even the genus, referred to by Mr Dolbear ? There are 



