The Tobacco Slug. 31 



laid more eggs tliat failed to hatch than others. Under natural con- 

 ditions it may be expected that the number of eggs laid and their 

 vitality will be greater than in breeding jars. We have, therefore, 

 no reason to discount the egg-laying powers of the beetles. 



AVhen the female has started egg-laying, she lays practically 

 every day. The greatest number of eggs found for one day was 69, 

 and the average for the whole egg-laying period 22. The greatest 

 number of eggs obtained from one female was 2421, and the average 

 number 1225. The egg-laying period lasted from fifteen to one 

 hundred and twenty-four days, with an average of sixty-five, the 

 time spent in hibernation not included. 



The Larva. — The larva, on hatching, starts feeding at once, and 

 grows rapidly. The first moult takes place when it is two to four 

 days old and about one-tenth of an inch long. The second when it 

 is from four to seven days old and about an eighth of an inch long, 

 and the last moult when it is from six to ten. days old and about a 

 quarter of an inch long. The larva is ready to enter the ground two 

 to four days later. The actual period of larval life before entering 

 the soil was found to be from seven to fourteen days. In summer 

 eight to ten days was the general rule. 



Tbe larva collects its excrement in a soft mass on its back, and 

 from time to time the excess drops off. The excrement is moved 

 forward from behind by undulating motions of the body. The mass 

 appears to be kept moist by a liquid from the anus. The slimy cover- 

 ing increases the slug-like appearance of the larva. When disturbed 

 the larva flings back its head, and a greenish liquid issues from its 

 mouth. When the disturbance has passed off, it slowly sucks this 

 liquid back, moving its jaws during the process. 



The Cocoon.- — When ready to pupate the slug enters the soil and 

 forms a cocoon with a white froth from its mouth. It must be more 

 or less covered to be able to construct its cocoon, as on the surface, or 

 when only slightly covered, it wastes much of the foam without 

 succeeding in surrounding itself theiewith. If it cannot form a 

 cocoon, the larva may pupate naked. 



In the field cocoons occur at the base of the tobacco plants, from 

 one-half inch to one inch down in the soil. Larvae maturing in the 

 tobacco sheds usually drop to the ground, and their cocoons have been 

 found in loose soil on the floor. Some may form their cocoons in the 

 hanging tobacco. Cocoons have been observed in cracks in a rafter 

 of a tobacco shed, but this is an unusual position, aud probably at 

 some time infested tobacco had been hanging in contact with the 

 rafter. 



The Piipa.—Vw^diQ were found in the cocoons three days after 

 these were constructed. The pupal stage of naked insects was found 

 to be from six to eight days. Beetles which develop in cocoons 

 apparently wait a few days before they emerge, if undisturbed. The 

 time from when the slug enters the soil to the emergence of the 

 beetle has been found to be from ten to nineteen days, and the full 

 period from the hatching of the egg to the emergence of the beetle 

 from seventeen to thirty days, the longer developments being those 

 early in the season and the shorter those in summer. 



The Adult.— T^ie beetles are comparatively long lived, but occa- 

 sionally an exceptional one is found dead after a few days. Under 

 observation the long-est lived females were those which hibernated. 



