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. 23 o, c) , which holds the spring when it is folded under the abdomen. 



The spring or Jurcitla (Fig. 230, s) is fonned 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 tnanubrmm (Fig. 234, ma); the 

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

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



In the Entomobryidae 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 Poduridaj the. furcula is wanting. 



The order Collembola includes two quite distinct 

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

 elongate with 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; 

 mu, left muc- 

 ro. (After 

 Lubbock,) 



A. Body elongate Suborder Arthropleona. 



AA. Body globose Suborder Symphypleona. 



SUBORDER ARTHROPLEONA* 



In this suborder the body is elongate v/ith dis- 

 tinct segmentation (Fig. 235). The three thoracic 

 and six abdominal segments are distinct as a rule; 

 the exceptions apply only to the last two or three 

 abdominal segments. The heart is furnished 

 with six pairs of ostia. The tracheae are wanting; 

 these insects live in damp situations and apparent- 

 ly breathe through the surface of the body. This 

 suborder includes two families, which can be sep- 

 arated as follows : 



A. Furcula present or absent ; when present clearly ap- 

 pended to the fourth abdominal segment . .Podurid^e 



AA. Furcula present and apparently appended to the 

 fifth abdominal segment Entomobrvid^ 



Family Podurid^ . — Among the better-known 

 members of this family are the following: The 

 "Snow-flea," Achorutes nivlcola, which occurs 

 abundantly in winter on the stirface of snow (Fig. 

 235); this species is also known as Achorutes 

 socidlis. Achorutes armdtus is often found on fungi. 



Fig. 235. — The rnow- 

 fiea, Achorutes Tih'i- 

 cola. (After Fol- 

 som.) 



* Arthropleona : arthron (dpdov), a joint; pleon, a crustacean's abdomen. 



