HOW INSECTS WALK ON SMOOTH SURFACES ll;j 



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In the spherical last tarsal joint of Orthoptera (Fig. 109), which is without 

 these tenent hairs, nearly all the cells of the hypodermis are converted into uni- 

 cellular glands, each of which sends out a long, fine, 

 chitinous tubule, which is connected with its fellows by jj ^ 



very fine hairs and is continuous with the chitinous 

 coat of the foot and opens through it. The sole of the 

 foot is elastic and adapts itself to minute inequalities 

 of surfaces, while the anterior of each tarsal joint is 

 almost entirely occupied by an enlargement of the 

 trachea,* which acts on the elastic sole like an air 

 chamber, rendering it tense and at the same time 

 pliant. Dewilz adds that the apparatus situated on the 

 front legs of the male of Stenobothrus sibiricus (Fig. 

 131) must have the function of causing the legs to 

 adhere closely to the female by the excretion of an 

 adhesive material. The hairs of the anterior tarsi of 

 male Carabi also appear to possess the power of adhe- 

 sion. In the house-fly the empodia seem to be only 

 called into action when the insect has to walk on 

 vertical smooth surfaces, as at other times they hang 

 loosely down. 



Burmeister observed the use of a glutinous secretion 

 for walking in dipterous larvee, and Dewitz found that 

 the larva of a Musca used for this purpose a liquid 

 ejected from the mouth. The larva? of another fly 

 (Leiifopis puncticornis) perform their loop-like walk 

 by emitting a fluid from both mouth and anus. A 

 Cecidomyia larva is able to leap by fixing its anterior 

 end by means of an adhesive fluid. The larva of 

 the leaf-beetle, Galeruca, moves by drawing up its 

 hinder end, fixing it thus, and carrying the anterior 

 part of the body forward with its feet until fully 

 extended, when it breaks the glutinous adhesion. The 

 abdominal legs of some saw-fly larvae have the same 

 power. 



Dahl could not detect in the foot of the hornet (ye spa crabro) any 

 space which could be considered as a vacuum. 



Simmermacher states that in 

 most cases of climbing beetles the 

 tubular tenent hairs pour out a 

 secretion (Figs. 1,33, 134), "aud it 

 is probable that we have here to do 

 with the phenomena not of actual 

 attachment by, as it were, gluing, 

 but of adhesion ; the orifice of 

 the tubes is divided obliquely, 

 and the tubes are, at this point, 

 extremely delicate and flexible, 

 so as to adhere by their lower sur- 



FIG. 130. A, end of an 

 adhesive hair of a weevil 

 (Kii]iolus) : i", canal: /"', 

 its external opening 1 at the 

 end of the hair. , end of 

 a similar hair of Telephorus 

 with drops of the secretion. 

 After l)e\vitx. 



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P 



Fro. 131. Slenobotlirux ftibiricits pair- 

 ing : .4. the J 1 , fore tarsus (/) greatly enlarged ; 

 at', arolia ; ]>, pulvillus. After Pagenstecher. 



