150 Mr Burkill, On the Fertilisation of some [Feb. 12, 



(Sc. and Carab.) very abundant. Muscinae: — 52 and 53, 2 species 

 not identified (Sc). 



Hemiptera: — 54. Sipho7iophora artemisiae Koch (Camb.). 

 56. Aphis sp. (Sc). 



Neuroptera: — 56. Thrips sp. (Sc). 



Besides these m^Qci^ Heterocordylus sp. juv. (Hemiptera) and 

 Homalonotus aeneicoUis Sharp (Coleoptera)were frequently observed 

 running about the spikes of flowers, and may occasionally explode 

 the flowers with their legs. 



Fertilisation. This is my list of visitors to a plant which Hens- 

 low quotes as being a widely distributed self- fertilising flower \ 



By finding the average rate of withering of a flower after 

 explosion and consequent fertilisation, I was able in June 1893 at 

 Scarborough to make the following calculation : — At times when 

 the flowers required 2 to 5 five hours to wither after explosion 

 (fine warm weather), the following percentages of open flowers 

 were found to be exploded: 29Vo, 247o, ^"/o, 87o, ISVo— the average 

 being 18Yo- Taking the average rate of withering to be 4 hours, 

 then 4'5*'/o of the flowers in blossom were exploded every hour, 

 and in such weather the average duration of 22 hours (nearly 2 

 days of 12 hours) should be sufficient to permit of the explosion 

 of every flower. Such about is their duration, but they ensure 

 themselves against accidents by becoming self-fertilised. 



Now comes the question — what insects do the work of fertili- 

 sation ? Miiller^ in Germany and Knuth'' on the Friesian islands 

 attribute this work to the Hive-bee : it is not so in England as far 

 as my observations extend. 



At Scarborough Platychirus manicatus, and at Cam- 

 bridge Halictus morio and Scatophaga, were the most 

 efficacious visitors. The flowers were watched at all hours 

 of the day from 4 a.m. to 10 p.m. 



Of these insects which I have seen on the flower nearly all are 

 capable of causing explosion. I have seen Scatopse brevicornis 

 both at Scarborough and Cambridge, and a Gryptus at Scarborough, 

 entrapped by the explosion of stamens of the flower, shewing 

 that these — almost the least insects in this list — were just strong 

 enough to effect it. 



In order to see if those flowers which remained open all night 

 received visitors, spikes were marked and flowers on them found 

 exploded in the early morning; and further, in the twilight (9.30 

 and 9.35 p.m.) I have twice seen a beetle settle on the heads and 

 apparently seek for honey. 



^ On the Self- fertilisation of Plants. Trans. Linn. Soc. Series ii. Vol. i. (Bot.) 

 p. 392. 



2 Fertilisation of Flowers, p. 180. 



^ Blumen u. Insekten auf den Nordfriesischen Inseln, Kiel, 1894. 



