34 EESULTS FROM GIPSY MOTH PAEASITE LABORATOEY. 



kind, the requirements for investigating these most interesting phe- 

 nomena, where the more common species are concerned, being, as 

 stated by Dr. L. O. Howard, " simply good laboratory facilities and a 

 skilled technique, together with trained powers of observation." 

 These, as he pomts out, are to be found in many institutions and 

 with many individuals in this country. The element of a chance 

 discovery sometimes enters into consideration, however, even when 

 a common insect is made the subject of study. Quite as often as not 

 the discovery of the thread which will later lead to an unravehng of 

 the complete life liistory is notliing more nor less than an accident, the 

 clue being stumbled upon in a place and at a time altogether unlocked 

 for. The investigations of the life history of Perilamjms Tiyalinus Say 

 received their initial impetus from just such an accidental discovery. 



BIOLOGY OF PERILAMPUS HYALINUS SAY. 



When time and opportunity have permitted, the parasites of certain 

 among the native leaf-feeding caterpillars have been studied at the 

 Gipsy Moth Laboratory in order to determine the part which parasitism 

 plays in their natural control, and in an endeavor to arrive at a better 

 understanding of the varied phases of the problem. Among others, 

 the fall webworm (Hyphantria textor Harris) was selected as a prom- 

 ising subject, and, coming as it does at a season just after the sum- 

 mer's work on gipsy moth parasite importation and colonization is 

 over, it has been possible to devote a larger share of our attention to it 

 than to other even more interesting species which complete their trans- 

 formations earher in the season. Upon several occasions the young 

 caterpillars have been brought in from the field, placed in insect-proof 

 rooms and cages, and fed. In due time primary parasites, usually 

 tacliinids, species of the ichneumonid genus Limnerium, and occasion- 

 ally Apanteles, emerged from these caterpillars, and the cocoons and 

 puparia were removed to tightly stoppered vials and placed aside for 

 the emergence of the adults. Later examination revealed the fact 

 that adults of the species which formed the puparia or cocoons could 

 not always be expected to emerge, for usually a certain percentage 

 produced adults of Perilampus instead. How the adult female Peri- 

 lampus obtained access to these puparia and cocoons in order to ovi- 

 posit in them was a mystery inasmuch as especial pains had been 

 taken to make the rooms and cages containing the caterpillars para- 

 site-proof. But for a fortunate discovery during the spring of 1909 

 the true significance of these perplexing observations would doubt- 

 less have remained a mystery for some time to come. 



While engaged in experimentation for developing a better technique 

 in the preparation of hymenopterous larvse for microscopical study, 

 in wliich work the larvae of the common Limnerium validum Cresson, 

 an important parasite of the fall webworm, were used as subjects, a 



