10 THE HUMBLE-BEE I 
with a good lens, the fore-wing is seen to have a 
fold along its posterior margin, while on the anterior 
margin of the hind-wing a row of hook-shaped 
bristles or hairs can be easily detected. When the 
wings are expanded these hooks catch on firmly to 
the fold in the fore-wing, and the fore- and hind- 
wing on each side are enabled to act in concert, 
having the appearance and all the firmness of a 
ea 
single membrane. In the humble-bees the wing- 

Fic. 2.—Antenna-cleaner in fore-leg. 
hooks number from 17 to 24. Their position is 
indicated in Fig. 25, p. 145. 
Another remarkable structure is an antenna- 
cleaner in the front legs. This consists of a semi- 
circular incision in the metatarsus, fringed with a 
fine comb. When the leg is flexed a knife-like 
spine hinging from the tibia can be made to shut 
down over the incision. Thus a hole is formed 
through which the antenna is frequently drawn to 
rid it of any pollen grains or particles of dust that 
may have clung to it. 
1 Fauna of British India—Hymenoptera, by C. T. Bingham, 1897, vol. i. 
pp. viii and ix, 
