316 MOTIONS OF INSECTS. 



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, flexible transparent threads covered with 

 a slimy secretion. By these, when it has lost its hold, 

 it adheres to the surface on which it is stationed \ An- 

 other insect related to the common sugar-louse, and 

 called by Latreille Machilis poli/poda^ 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 with 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 ceilings, and up perpendicular surfaces 

 even when of glass — it afibrds 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 position) 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. 



The first order of climbers — those that climb by 

 means of their clWiSos — includes a large proportion of 



■'• De Geer,vii. 38—. /. iii./. 10. rr. 



^ This insect aboiincls. at East Farleigh, ncai- Maidstone. 



