80 RESULTS FROM GIPSY MOTH PARASITE LABORATORY, 



LENGTH OF THE STAGES IN THE LIFE HISTORY OF LIMNERIUM. 



From this niul the preceding experiments we may estimate that the 

 duration of the omliryonic development of Limnerium validum, or 

 the time from oviposition to the hatching of the egg, is about G to 8 

 days; that the hirval developmental period lasts for about 24 to 33 

 days ; and that the pupal period, or, more exactly, the time from the 

 spinning of the cocoon to the eclosion of the adult, is about 13 to 22 

 days, or much longer. The length of the larval period within the 

 cocoon before pupation was not determined, but, judging from the 

 cocoons examined on December 13, it may be extended several months. 

 The minimum time from egg to imago is thus about T weeks, or 

 50 days, whereas the maximum time to the eclosion of the adult may 

 be many months, due to quiescence within the cocoon. This species 

 hitherto has been considered to have a single generation a year, but 

 this last experiment seems to indicate that under certain conditions 

 at least it is able to pass through two generations annually. Under 

 normal conditions, however, there is much doubt wdiether more than 

 one generation actually occurs in the Northern States. 



A POSSIBLY NORMAL PARASITE OF MALACOSOMA. 



This experiment shows that Limuer'/inn valklum, is a possibly nor- 

 mal parasite of the tent caterpillar, although it has never been found 

 attacking that species in the field. The reason for this is obvious: 

 The tent caterpillars hatch early in the spring, long before the L'tm- 

 neriwn leaves its cocoon, and therefore are not in season for this para- 

 site. From the fact, however, that nearl}^ one-half of the caterpillars 

 dissected in this experiment were found to be parasitized, and that 

 comparatively few were killed by Umrj/'Hiun, we may conclude that 

 Limnerium valid urn is only partially adapted to this host. In the 

 dissecting work only 5 dead larvjp or eggs were discovered, but many 

 more without much doubt succumbed to the defensive reactions of 

 the host. In the 42 caterpillars dissected, 23 eggs or larva^ were 

 found, and 29 other larvae w^ere successful in passing through their 

 larval development, making a total of only 52 parasites that came 

 under observation. If the 5 females used in this experiment ovi- 

 posited as freely, hoAvever, as those in the ]>receding experiments, and 

 there is no reason to l>elieve otherwise, some 100 to 200 eggs or even 

 more were i)robably laid. Taking 100 as a conservative estimate, 

 and with due allow^ance for the destruction wrought by the dissec- 

 tions, we may thus figure on a mortality of at least about 37 per 

 cent. The cast eggshells were almost invariably found thickly en- 

 sheathed with amo'bocytes, and the function of the latter was without 

 doubt the same as in the case of the brown-tail moth caterpillars, 

 to disintegrate if not to kill the young larvae. In the present instance, 



