MATING HABITS. 



237 



Tabi,E 104. — Number of eggs and number of batches of eggs laid by diiferent species 



of the genus Leptinotarsa. 



Species. 



Average 



number of 



eggs. 



Average 



number of 



batches. 



Average 



length of 



egg-laying 



period 



in days. 



Variation in egg-laying. 



Maximum 



number of 



eggs. 



Minimum 



number of 



eggs. 



Maximum 



number of 



batches. 



Minimum 



number of 



batches. 



Iv.decemlineata. . 

 multitaeniata. . 



oblongata 



rubicunda 



undecimlineata 

 signaticollis . . 



dilecta 



dahlbomi 



violescens 



lacerata 



modesta 



zetterstedti . , . 

 rubiginosa .... 

 haldemaui. . . . 

 lineolata 



450 

 425 

 300 

 300 

 400 



425 

 200 



175 

 175 

 250 

 270 

 200 

 200 



175 

 200 



12 

 10 

 10 

 10 

 12 



6 



12 



14 



8 

 7 

 7 

 9 

 II 

 6 

 7 



30 

 30 

 25 

 30 

 25 

 35 

 15 

 20 



14 

 20 

 20 

 20 

 20 



23 

 22 



600 



783 

 448 

 372 

 621 



643 

 310 

 242 

 210 



IT. 



242 

 260 



234 

 300 



190 

 211 

 114 

 185 

 154 

 396 

 107 



31 

 10 

 200 

 200 

 176 

 140 

 152 

 109 



18 

 22 

 14 

 14 

 20 

 12 



15 

 20 

 10 

 12 

 14 

 13 

 17 



4 

 5 



4 

 3 

 7 

 6 



4 

 5 



10 



10 



6 



6 



5 

 6 



7 

 8 

 8 



Concerning the breeding habits of these beetles three facts have been 

 learned which are of importance in succeeding studies. First, the habits of 

 these beetles in normal reproduction are promiscuous ; hence the offspring from 

 any one female may have several different male parents, and from material 

 taken in nature in copulation or otherwise we can not be sure of results in 

 breeding experiments until we have reared such material in experiment for at 

 least one or two generations, and are certain of the purity of the race under 

 experimentation ; second, the eggs are laid and developed in batches, which in 

 the genital passages of the female do not mingle with successive batches — 

 that is, each is distinct from that which precedes and from that which fol- 

 lows — a fact that has been made great use of in the experiments in the pro- 

 duction of modifications ; third, the conditions of existence may prevent the 

 deposition of the eggs either through the inhibition of copulation or of the 

 development of the ova, or through the mechanical prevention of egg-laying 

 by the inability of the female to secrete in the accessory glands the fluid which 

 enables the eggs to pass easily through the lower part of the genital passages, 

 and which serves also to cement the eggs to the leaves. These three facts are 

 of paramount importance in the carrying on of continued and successful 

 experiments in pedigree breeding and in the experimental production of new 

 races and modifications. 



It has been clearly shown that there is not the slightest trace in the breeding 

 of these beetles of any selective influence due to color or form, that elaborate 

 mating habits are wanting, and that the sole means of sexual recognition is 

 through the olfactory sense and the odoriferous secretions of the accessory 



