234 LETTERS TO DR. RITZEMA BOS [CHAP. xxi. 



a few more of the " scabbed " potatoes, which it seemed 

 possible might be infested by Tylenchus devastatrix. If it 

 should be convenient to you at your best leisure to make 

 any examination, and to let me know results, I am sure I 

 need not say how acceptable your information would be, 

 not only to myself, but to many interested in the cause of 

 this external deformity. I send the potatoes in a little 

 tin box by parcel post. Recently I have had rather an 

 interesting observation of the little black, somewhat pubes- 

 cent, " ladybird " beetle, Scymnus minimus, as a feeder on 

 Red-spider, Tetranychus telarius. I have not been able to 

 find any account of its life history, so I have had great 

 pleasure in watching its progress from larval to imago state. 

 It seems to me to be greedily carnivorous ; after a few 



/ 



i, Cluster of eggs ; 2, egg, magnified ; 3, grub, magnified ; 4, line 

 showing natural length ; 5 and 6, pupae ; 7 and 8, 2-spotted lady-bird, 

 Coccinella bipunctata, L. (= dispar), and dark variety ; 9, 7-spotted lady- 

 bird, C. septempunctata, L., like in form but much larger than the black 

 lady-bird. 



FIG. 59. -LADY-BIRDS, COCCINELLID^E. 



hours' want of food during their journey to me, the larvas 

 set to work to feed on what they could pick up on the back 

 of a leaf infested by red spider, as eagerly as sheep on fresh 

 grass ; and as I found one day only a single larva remaining 

 of three or four confined together, I suspect it was this 

 survivor who had reduced his brethren to the small remains 

 which were all I found. The final changes were rapid, for 

 the above happened on August 28th, and shortly after it had 

 pupated, and yesterday I found the little black ladybird 

 in most active condition. 



I have heard nothing further at present from Mr. Roch- 

 ford about his Heterodera experiments. I think I must 

 remind him soon that he kindly promised me a report. 



