'°iyjl!''l I'l.NXKKDINGS OF THK N'ATIONAI. MlsKIM. 577 



as early as It^'.VJ hy l-'onscoloiiihc, l»iil it is ridiii Scli\\;ii/, (Aimr. 

 Naturalist, 18.S1, i»i>. Ol-G."}) that we have tlic must (Mrt'liil ;iccomit (»!' 

 the larval developinent. Wo (juote his words coiicerniii;,^ th.- larva' of 

 EuplectruH comstockil Howard : 



The iU)lic:itt' (•■jgshcU sjilits loii-^itiKlinally in tli« iiiidtllr of tin- back aiitl disclowH 

 the white hiiva of tlie parasite, whieii {^ratlually works tlie ej^jrshell iiioie itml mom 

 (lowu the sides of its body where, for some hours, it remains visible as a bhuk line, 

 but within less than twelve honrs it disappeurs from view beneatii tlie rapidly ^row- 

 iii;,' parasite larva. This last, as soon as it has free 1 its liead from the e<;^sh<dl, 

 pierces the skin of its victim and thereafter remains stationary with its liead buried. 

 As soon as it has fairly begun to feed, the white color changes ton bright blnish- 

 green, and tlie segments and spiracles which in the newly hatched larva were barely 

 visiliie under higli magnifying power are now readily seen. The growtli of tlio 

 larva is very rapid, i»ut seems to vary according to the season, averaging tiirei- davs 

 in August and four daj's in September. When full grown the larva- crowd each 

 other, and if there are five or more of them on a caterpillar they form a semi- 

 globular lump of very striking appearance. L'sually their growtli is uniform, und 

 retardation in development of individuals in the group results in death. When full 

 grown they turn yellowisli-white and relax their hold. 



Tlu> worm which up to this time showed no signs of liring allecied, exceiit bv its 

 sickly yellowish color and by its very slow growth, collapses and dies as soon as a 

 single one of the parasitic larvic withdraws, and the same fate overtakes those 

 Iliiplectrus larva' which are at the time less advanced in their development or im- 

 mature. If one of the parasitic larv:e be removed by hand both the victimized 

 worm and the remaining parasites (juickly dry up. 



The presumption that the Euplectrns larv:e may migrate from one worm to 

 .inotlur is unfounded. They alw.ays remain stationary on the W(Uin. which the jmrent 

 lly has chosen as its victim, and they never even move from the spot where the egg 

 has been laid until tliey are full grown. Every attempt I made to transplant a larva 

 from one worm to another invariably resulted in the death of the itarasito. 



These ob.servations may be eoinpared with the ac(!oiiiits of e.xtenial- 

 feedin^' ichiieiiinonid larva' by De (reer, Newport, Fitch, and Poiilton. 



HOW FAST DOES IT DEVELOP * 



There is evidently considerable variation in the rapidity of «levelop- 

 ment of the elialcidid larva', and consecpiently t)f the number of an- 

 nual <i:enerations. This variation is in part accordinj:' to the particular 

 parasite and in part to the habits of the particular host-insect. It is 

 rather more lajiid as a {general thin.u', however, with iUv ('hdlri'iidw 

 than with citlier t lie />'/vffo?j/'/'f (»r Ihv fclnieiimonidd'. h'at/ebur^ has 

 shown that in \']\\Vi)\)v rirroinnliis jiKpnnnn occupied on one occasion 

 from June 11 to duly It to iimlerg;o its entire transformations from v<x>r 

 to adult — thirty-seven tlays ; but in this country NN'ebster has recorded 

 an instance {Insect Life, I, 2L*5) in which the ejj;;s of the same parasite 

 were laid Auirnst 1), the adidt insect developing; .\.u<;ust 137 — .sevente«'n 

 days later. Hubbard has noted (Fourth IJeport V. S. lint. Com.. 

 p. UKi) that the egfjj of Aletid .rylina ^ives forth the adidts of Tri- 

 vhoijramma prctiosa on the seventh day after it was stuuij by their 

 l)arents. Eiiphrtrxs tninstitc]:ii has been shown by Schwarz to dcvcloi) 

 from etju: to adult in Alabama in midsummer in seven days, 



ri<H-. N. :m. ".»1 ;i7 



