318 KANSAS UNIVERSITY SCIENCE BULLETIN. 



This defensive organ probably explains the fact that mole 

 crickets have so few natural enemies, as reported by Bar- 

 rett (1). 



Since the Gryllotalpidae move most of the time in under- 

 ground burrows the discharge from the anus would protect 

 against attacks from the rear. Hence there is no discharge 

 when the irritation is on the anterior half of the body. The 

 head and thorax, besides being very hard, are further pro- 

 tected by the powerful fore legs. The abdomen is compara- 

 tively soft and without other protection than that described 

 above. 



My observations and experiments prove conclusively that the 

 secretion of the anal glands, or "prostatic glands" of Berlese 

 and Fenard, is preeminently protective, as any one who will 

 take the trouble to secure a live specimen and repeat these tests 

 can see for himself. Neither Berlese nor Fenard can have 

 handled live individuals, or they should have seen the use of the 

 anal secretion. 



As far as we know no other orthopteran has these protective 

 glands, nor has it the same peculiar habits. The mole crickets 

 running along the narrow underground tunnels have the soft 

 abdomens constantly exposed to the attacks of enemies which 

 they cannot see or perceive, so they have developed a special 

 organ which can instantly repel or retard a pursuer. 



SUMMARY. 



1. The species of Gryllus in eastern and central United 

 States are not distinct, but form one large intergrading series, 

 as Lutz has shown. This is true also for the supposed dis- 

 tinguishing st7'aiv and dark colors as shown by the specimens 

 collected in Texas. 



2. The female mole cricket has a partially developed chirp- 

 ing organ on its elytra. With this instrument it produces a 

 single note used as means of recognition in the dark tunnels. 



3. The anal gland of Dufour, the prostatic gland of Berlese 

 and Fenard, is protective in function. The secretion operates 

 as a repellant by its fetidity, and as a retardant by its 

 stickiness. 



4. Both the female musical organ and the protective gland 

 are adaptations to life in underground tunnels. 



University of Kansas, 

 May 10, 1909. 



