180 INJURIOUS INSECTS 



this time that they wander in the day time, dropping on 

 persons by their silken threads, and crossing the side- 

 walks of our cities in all directions. It is from this habit 

 of dropping upon persons, that they have been called 

 " Drop- worms." A wise instinct urges them to thus 

 wander from place to place, for, did they remain on the 

 tree, they would soon multiply beyond the power of that 

 tree to sustain them, and would in consequence become 

 extinct. When they have lost their migratory desires, 

 they fasten their bag very securely by a strong band of 

 silk to the twigs of the tree on which they happen to be. 

 Here again a strange instinct leads them to thus fasten 

 their cocoons to the twigs only of the tree they inhabit, so 

 that these cocoons will remain through the winter; and not 

 to the leaf stalk, where they would be blown down with the 

 leaf. After thus fastening their bags, they line them with 

 a good thickness of soft white silk, and after turning 

 around in the bag so as to have the head towards the 

 lower orifice, they rest awhile from their labors, and at 

 last cast their skins, and become chrysalids. Hitherto 

 the worms had all been alike in appearance, but now 

 the sexes are distinguishable, the male chrysalis (fig. 113, 

 b), being but half the size of that of the female, and ex- 

 hibiting the encased wings, legs, and antennae, as in all 

 ordinary chrysalids, while hers show no signs of any such 

 members (see inside of bag at e). Three weeks after- 

 wards, a still greater change takes place, the sexes differ- 

 entiating still more. The male chrysalis works himself 

 down to the end of his bag, and, hanging half-way out, 

 the skin bursts, and the moth (fig. 113, d), with a black 

 body and glassy wings, escapes, and, when his wings are 

 dry, soars through the air to seek his mate, who is not 

 blessed with wings, but is an abortive affair, with the 

 head and general appearance of the larva, but still 

 more degraded, since she has not even the legs which 

 it possessed; she is, in fact, a naked, yellowish bag 



