INFLUENCE OF TEMPERATURE ON DIFFUSION. 



91 



Further observations made by Mr. Urbalms on these same dates 



with eight additional females, the offspring of which were not counted, 



are of much interest and are given herewith. 



January 3. Two reproducing. 

 January 4. Four reproducing, 1 pupating. 

 January 5. Five reproducing. 

 January 6. All torpid, seemingly frozen. 

 January 7. All torpid, seemingly frozen. 

 January 8. All torpid, none reproducing. 

 January 9. Seven reproducing, 1 still pupa. 

 January 10. Seven reproducing, 1 still pupa. 

 January 11. All torpid, seemingly frozen. 

 January 12. All torpid, seemingly frozen. 

 January 13. All torpid, seemingly frozen. 



January 14. Adults and young fallen from the plants and lying on the ground. 

 All except 3 inactive. 



One female of the first five died on the 10th and nearly all of the 

 others survived but a few days; only one was alive on the 20th. 



During the spring of 1908 the junior author was engaged in an 

 extensive series of rearing experiments at Richmond, Ind. Both 

 plants and insects were kept out of doors in a small rearing house 

 (see PL II, fig. 1), with a thermograph placed in their midst, so that 

 exact temperature changes were continuously recorded. Plants 

 were grown in flowerpots and over them in each case was placed a 

 lantern globe with the top covered with cheesecloth. Whatever 

 the effect of this inclosure and cover might have been it was evi- 

 dently uniform and, therefore, affected all of the viviparous female 

 Toxoptera on these plants to the same degree. 



Taking five viviparous females, each a stem mother, colonized 

 separately on single plants, in a precisely similar inclosure, and keep- 

 ing a record of the number and date of young born, we have the fol- 

 lowing tabulated results : 



Table XI. — Effect of temperature on reproduction of Toxoptera graminum, Richmond, 



Ind., 1908. 



Date. 



Apr. 18. 

 19. 

 20. 

 21. 

 22. 

 23. 

 24. 

 25. 

 26. 

 27. 

 28. 

 29. 

 30. 



Tempera- 



ture. 



Mini- 



Maxi- 



mum. 



1 



mum. 



°F. 



°F. 



55 



63 



50 



70 



39 



68 



33 



68 



35 



74 



52 



79 



60 



71 



61 



74 



53 



80 



42 



67 



38 



54 



36 



46 



33 



47 



Number young pro- I To- 

 duced by each in- i tal 

 dividual*. No, 





2 







2 



2 



1 



2 



2 







2 



2 



1 



1 



1 



1 



5 



5 



1 



3 



4 







4 



5 



1 



5 



3 



3 



2 



2 



3 



















2 



3 















6 

 11 



6 



7 



6 



14 



11 



15 



14 



S 



2 



7 







Date. 



May 1. 

 2. 

 3. 

 4. 



Tempera- 

 ture. 



Mini- 1 Maxi- 

 mum, mum. 



°F. 

 29 

 35 

 37 

 41 

 49 

 49 

 41 

 41 



'F. 



56 

 47 

 55 

 50 

 52 

 76 

 63 

 49 



Total.... 



Total progeny during 



life 



Number young pro- 

 duced by each in- 

 dividual*. 



29 j 32 

 60 47 











2 



1 



2 



2 



















2 



2 



o 



1 







o 



To- 

 tal 

 No. 



