BAGWORM MOTHS OF THE WESTERN HEMISPHERE 9 



of Oiketicus kirbyi from Costa Rica is rather constant; hatching 

 usually occurs within 29-33 days. 



Larva, — The length of time required for this stage varies also 

 with the species and sometimes considerably within a species. 

 Several bagworms overwinter in this stage (usually as a last instar 

 larva), but the shortest tmie spent by any species as a larva is approxi- 

 mately two to three months. The larval period of some of the larger 

 tropical species is evidently very extended. 0. kirbyi (in Costa Rica) 

 has been observed by Stephens to require as long as 382 days for 

 maturity, with considerable variation in the length of time. Con- 

 sidering such information, it is perhaps superfluous to mention that 

 rarely is there more than one brood per year, but a second generation 

 may be completed by some psychids inhabiting the warmer climates. 



Very little is known about the nmnber of larval instars, owing in 

 part to the concealed nature of the moulting process (performed 

 entirely within the case) and to the immediate eating of the cast skin 

 by the larva. Jones and Parks (1928) briefly mention that there 

 are "four or more molts." An actively feeding bagworm, when 

 preparing to shed its cuticula, normally will attach its case and 

 tightly close the anterior end as if preparing for pupation. Stephens, 

 in recording the number of tunes this interruption occmTed, concluded 

 that 0. kirbyi underwent approximately 12 to 20 molts during its 

 larval history. 



Apparently this family does not contain a single species which dem- 

 onstrates host specificity. The polyphagous habit is well represented 

 throughout the family, recorded hosts of many bagworms being 

 numerous and widely varied. The more primitive members of the 

 Psychidae, the so-called Micro-Psychina, are more prone to be scav- 

 engers, feeding on lichens and other low plant forms, and even resorting 

 to an insectivorous diet at times. These tendencies also are carried 

 over to the Macro-Psychina to some extent, but in this group the 

 higher plant forms are preferred. 



Even though the host range of most bagworms is frequently rather 

 extensive, several species show a great reluctance to change food plants 

 abruptly within the larval life. For many of these insects there seems 

 to be a very definite preference for a single food plant, usually the 

 host upon which the young larva first commenced to feed. Jones and 

 Parks (1928) stated their belief that "food-plant choice by the young 

 larvae rests on an inherited preference as well as on early proximity 

 and reluctance to change. In this way impermanent food-plant races 

 persisting for a number of years often result." This reluctance of a 

 larva to feed successively on different plants probably varies with each 

 species. The present writer, in rearing numerous larvae of 0. platensis, 

 observed that the insects feed indiscriminately on a wide variety of 



