EXTERMINATING NOXIOUS INSECTS. 265 



together upon a common web for two or three days, and 

 during these periods though more active than most other 

 caterpillars in this so-called sickness they are quite slug- 

 gish. During the last or fourth moult they frequently 

 come low down on the trunk of the tree, and, as in the case 

 of the gregarious larvae of the Hand-maid Moth (Datana 

 ministra), which often denude our black- walnut trees, they 

 unwittingly court destruction by collecting in such masses 

 within man's reach. From the time they are born till after 

 the third moult, these worms will drop and suspend them- 

 selves mid-air, if the branch upon which they are feeding 

 be suddenly jarred. Therefore, when they have been al- 

 lowed to multiply in an orchard, this habit will suggest va- 

 rious modes of destroyiug them. They can often be slaugh- 

 tered en masse when collected on the trunks during the last 

 moulting period. They will more generally be found on 

 the leeward side of the tree, if the wind has been blowing 

 in one direction for a few days. The cocoons may also be 

 searched for, and many of the moths caught by attracting 

 them towards the light. But pre-eminently the most effect- 

 ive artificial mode of preventing this insect's injuries is, to 

 search for and destroy the egg-masses in the winter-time, 

 when the trees are leafless. This course is the more effi- 

 cient because it is more easily pursued, and nips the evil in 

 the bud. Tarred bandages, or any of the many remedies 

 used to prevent the female Canker-worm (p. 233) from as- 

 cending trees, can only be useful with the Forest Tent-cat- 

 erpillar, when it is intended to temporarily protect an unin- 

 fested tree from the straggling worms which may travel 

 from surrounding trees. 



The Codling-worm Moth. Doubtless most persons who 

 are in the habit of eating crude apples have repeatedly no- 

 ticed the little whitish worm which is so often found bur- 

 rowing at the core of the fruit, and filling it with its dis- 



12 



