228 



AN INTRODUCTION TO ENTOMOLOGY 



collophore bears at its extremity a pair of eversible sacs through the 

 walls of which exude a viscid fluid. By means of this organ these 

 insects are enabled to cling to the lower surface of smooth objects. 

 The collophore is developed from a pair of appendages, which in the 

 course of their development become fused together at their base. 



The third abdominal segment usually bears a pair of short append- 

 ages, whose basal segments are fused; this is the tenaculum, or catch 

 (Fig. 230, c), which holds thespring when it is folded under the abdomen. 



The spring or furcula (Fig. 230, s) is formed by the 

 appendages of the fourth abdominal segment which are 

 united at the base but separate distally. These ap- 

 pendages are three-jointed. The united basal seg- 

 ment is termed the manubrium (Fig. 234, ma); the 

 intermediate segments, the denies (Fig. 234, d); and 

 the terminal segments, the mucrones (Fig. 234, mu). 



In the Entomobryidse the furcula appears to be 

 formed by the appendages of the fifth abdominal seg- 

 ment; but a study of the muscles that move it shows 

 that it really pertains to the fourth segment. In some 

 genera of the Podurid^ the furcula is wanting. 



The order Collembola includes two quite distinct 

 types of insects; in one of these types the body is 

 elongate w4th distinct segmentation; in the other 

 the body is shortened, the abdomen globose and its 

 segments in part fused. Based on this distinction the 

 order is divided into two suborders as follows : 



Fig. 234.— The 

 furcula of Pa- 

 pirius: ma, 

 manubrium; 

 d, left dens; 

 mil, left muc- 

 ro. (After 

 Lubbock,) 



A. Body elongate Suborder Arthropleona. 



AA. Body globose Suborder Symphypleona. 



Fig. 235. — The rnow- 

 flea, A chorutes ni'vi- 

 cola. (After Fol- 

 som.) 



Suborder I. ARTHROPLEONA* 



Body elongate with distinct segmentation, rare- 

 ly with the last two or three segments of abdomen 

 partially fused; tracheae absent. 



Family i, Poduridae. Furcula, when pres- 

 ent, clearly appended to the fourth abdominal 

 segment; prothorax well developed; cuticula 

 usually granulated. 



Among the better-known members of this 

 family are the following: The "Snow -flea," 

 Achoriites nivicola, which occurs abundantly in 

 winter on the surface of snow (Fig. 235); this 

 species is also known as Achoriites socidlis. 

 Achoriites armdtus is often found on fungi. 



*Arthropleona : arthron (dpdov), 

 stacean's abdomen. 



joint; pleon, a cru- 



