Dec. 1, I860.] 



HARDWICKE'S SCI ENCE-GOSSIP. 



267 



THE INVASION OF LADYBIRDS. 



ON the first of last mouth (September) a friend, 

 who has a garden in the suburbs of this town, 

 brought me some young shoots from his apple-trees 

 clustered over with the dark grey Aphis {A. lanigera), 

 which gardeners call "American Blight." The 

 cottony fluff which surrounds these aphides was 

 mostly gone, but it had been originally very thick, 

 and nearly half an inch long. My friend also 

 brought me about fifty specimens of the large lady- 

 bird, Coccinella septem -punctata, which, he said, 

 swarmed upon the same apple-trees in such profusion 

 as he had never seen before. I have since been to 

 his garden, and kept some of the aphides and lady- 

 birds under a glass-shade for a fortnight. 



On every infested spray there were four distinct 

 forms of insect life besides the ladybirds, viz. : — 

 1. The unmistakable dark-grey aphis, about, T V of 

 an inch in length. 2. A creature of similar shape, 

 but of a reddish brown colour, only half the size, 

 and not nearly so abundant. 3. A black fly about 

 the size of the grey aphis, or a little larger, and with 

 four very delicate transparent and iridescent wings. 

 4. A minute whitish creature running about in a 

 lively manner, possibly a mite of some sort, but it 

 soon disappeared in captivity. 



The dark-grey aphides have long cottony hairs 

 growing from all parts of the abdomen— a row of 

 hairs on each segment — which break off close to the 

 body at the slightest touch. Globules of honey- dew 

 may often be seen exuding from their tails. They 

 cluster thick together, preferring the undersides of 

 the branches, and, with their heads downwards and 

 their abdomens tilted up, thrust their rostra through 

 the pores of the outer bark, and suck the descend- 

 ing sap. 



I imagine that the injury thus done to the vessels 

 of the inner bark checks the downward current of the 

 sap-stream, and that the cankerous swelling and 

 cracking of the bark are produced by its overflow. 

 Wherever these aphides have been numerous and re- 

 mained long the leaves are withered, aud the bark 

 cankered. But Nature preserves her balance. The 

 season which favours the aphides favours also the 

 seven-spotted ladybird, and these pretty beetles soon 

 find out their prey. The larva of the ladybird is sup- 

 posed to be much more voracious than the perfect 

 insect ; but no larvae were to be found in my friend's 

 orchard, and yet the aphides which, one Sunday 

 morning, seemed to have swathed all his apple- 

 trees in fine cotton, the next Sunday morning, when 

 he took his usual walk to the garden, had almost 

 disappeared. The cottony fluff was gone, most of 

 the branches were cleared of the invaders altogether, 

 or only spotted with their bleached and empty skins, 

 while the red-coated Coccinelke hung upon every 

 leaf and spray. 



The question may be asked, did the ladybirds 



eat the aphides, or did the aphides cast their skins, 

 become winged creatures, and fly away ? 



The evidence for the eating theory is, that the 

 ladybirds gathered on the very same trees as the 

 aphides ; that the aphides disappeared about the 

 time that the ladybirds arrived: that large numbers 

 of empty skins adhered to the boughs and lay on 

 the ground beneath; that when sprays, covered 

 with aphides, were inclosed for a fortnight with a 

 number of ladybirds, the latter were alive and well 

 at the end of the time, while, of the former, nothing 

 remained but skins ; and that on several occasions a 

 ladybird was seen with its mouth in contact with 

 an aphis, and its jaws moving. 



I am not able to say at what hours the ladybirds 

 took their food. I never saw them fairly and un- 

 mistakably at work. In the day-time they would often 

 run about a good deal, crawling over the masses of 

 aphides as if they were only little heaps of un- 

 attractive rubbish. Towards evening they would 

 cluster together and lie quiet. Perhaps they went 

 to sleep. Yet day by day, or night by night, the 

 aphides diminished, and in fourteen days they were 

 extinct. 



There is another question to settle. Are these 

 swarms of ladybirds immigrants into this country 

 from over the sea, or are they bred in the hop- 

 grounds ? We have no hop-grounds in Leicester- 

 shire, nor within a hundred miles of us, I think. 

 Persons who have been this summer on the eastern 

 and southern coasts assure me that clouds of 

 ladybirds were seen to come in from! the sea, 

 while others alighted in swarms upon ships in the 

 Channel ; and that the shore was, in some places, 

 so thickly covered with this living and crawling 

 red sand that it was impossible to walk without 

 crushing scores of them at every step. In the 

 Athenceum, of September 18th, is a paragraph men- 

 tioning that the Comic Almanack for 1848 repre- 

 sents Margate pier under similar circumstances, 

 as if it were a not uncommon occurrence; and 

 Loudon, in his " Encyclopedia of Gardening," alludes 

 to the same phenomenon on the shore at Brighton 

 in 1807. Now, if these insects migrate from the 

 hop-grounds in search of food, why should they con- 

 gregate on the barren shores ? If, in their wander- 

 ings, they came to the sea and were afraid to 

 venture out, one would imagine that they would just 

 turn back again. But supposing that they have had 

 a long and weary flight across the Channel, nothing 

 seems more natural than that they should settle 

 down on the first verge of terra firma to rest their 

 little tired wings. 



But why make this voyage across the water at all ? 

 And what brings them into Leicestershire ? On 

 either hypothesis they must have passed innume- 

 rable orchards, in which, no doubt, American blight 

 would be common enough before they reached my 



friend's little garden. 



And they must have had 



n 2 



