320 MOTIONS OF INSECTS. 



fork, ta^ a very singular organ, the use of which is to 

 prevent it from falling from a perpendicular surface, 

 on which they are often found at a great height from 

 the ground. Between the ends of the fork there is an 

 elevated cylinder or tube, from which the animal, 

 when necessary, can protrude two long, filiform, flex- 

 ible transparent threads covered with a slimy secre- 

 tion. By these, when it has lost its hold, it adheres to 

 the surface on which it is stationed*. — Another insect 

 related to the common sugar-louse, and called by La- 

 treille Machilis polf/poda (Lepisma, F.), in some places 

 common under stones'*, has eight pair of springs, one 

 on each ventral segment of the abdomen, by means of 

 which it leaps to a wonderful distance, and w ith the 

 greatest agility. 



Climbing is another motion of insects that merits par- 

 ticular consideration ; since, as this includes their power 

 of moving against gravity — as we see flies and spiders 

 do upon our cielings, and up perpendicular surfaces 

 even when of glass — it affords room for much interest- 

 ing and curious inquiry. Climbing insects may be di- 

 vided into four classes. — Those that climb by means of 

 their claws ; — those that climb by a soft cushion of 

 dense hairs, that, more or less, lines the underside of the 

 joints of their tarsi, the claw-joint excepted ; — those that 

 climb by the aid of suckers, which adhere (a vacuum 

 being produced between them and the plane of posi- 

 tion) by the pressure of the atmosphere ; — and those 

 that are enabled to climb by means of some substance 

 which they have the power of secreting. 



' De Geer, y\i. 38—. t. iii./. 10. fr. 



*• This insect abounds at East Farleigh, near Maidstone. 



