8 U.S. NATIONAL MUSEUM BULLETIN 244 



dental shipment of infested plant stock by human agencies as attested 

 by the relatively recent introductions of tlu-ee old world species 

 (Apterona crenulella f. helix, Epichnopterix pulla, and Fumaria casta) 

 into widely diverse regions of the Western Hemisphere. In addition, 

 Solenobia walshella possibly may have been introduced into this 

 country from Europe during colonial times. 



Certain biological adaptations of the Psychidae make such acci- 

 dental transportation very possible: the ability of the larva to resist 

 starvation for long periods of tune, the polyphagous feeding habit 

 (includmg, sometimes, the ability to subsist for brief periods on the 

 dried leaves of its own case), the habit of firmly attaching the bag 

 to almost any support for pupation, the high reproductive potential 

 of a single female, and the occurrence of parthenogenesis in a few 

 species. The last factor evidently has played a major role in the 

 establishment of Apterona crenulella f. helix in this country. 

 Theoretically, the successful introduction of a single egg is all that is 

 necessary for a parthenogenetic insect such as A. c. form hslix to 

 become naturalized in certain favorable habitats. 



Another means of dispersal of bagworms involves birds. An 

 unusual observation by J0rgensen (1954) needs more investigation. 

 He noted the viability of 30 or 40 larvae from eggs of Acanthopsyche 

 atra L. that reportedly had passed through the digestive tract of a 

 European robin (Erithacus rubecula). Mature females of this psychid 

 were fed to these birds, and larval emergence from the fecal droppings 

 were later observed. Small larval cases of other bagworms also have 

 been reported attached to the legs of birds. 



Wind dispersal of not only newly emerged larvae but also of various 

 later stages may be an important factor over short distances. Young 

 larvae, on emerging from the egg, often will spin silken threads and 

 engage in an activity generally referred to as "ballooning," the com- 

 mon practice of many species of spiders. Strong breezes are capable 

 of carrying these tiny larvae with their attached threads over short 

 distances. Windstorms would be even more effective and could 

 also aid in the dissemination of the more matm'e stages. Seitz (1912) 

 has reported finding, on the treeless pampas of Uruguay, large branches 

 of trees with living bagworms attached that obviously had been trans- 

 ported several miles by a violent storm (pampero). 



Egg. — The eggs, which may number from 200 for some smaller 

 species (Tutt, 1900) to as many as 6756 for the female of Oiketicus 

 kirhyi (Stephens, 1962), almost invariably are deposited in the larval 

 case, usually within the pupal shell that the female frequently 

 abandons. The length of this stage varies considerably depending 

 on the species; some (e.g., Thyridopteryx ephemeraeformis) pass the 

 winter in this state. Stephens (1962) has reported that the egg stage 



