IO THOS. H. MONTGOMERY, JR. 



10. Parasitic Hymeiwpicra in the Eggs of TJieridiuni. In 

 none of the cocoons raised by my captive spiders were there any 

 parasites, but about one out of every thirty or forty wild cocoons 

 was found to be infected with a tiny hymenopteron, black in 

 color, the males winged and the females wingless, of a length 

 somewhat less than the diameter of an egg of the spider. Prof. 

 Wm. H. Ashmead has kindly identified these as Proctrotrypids, 

 constituting a new species (montgomeryi) of the genus BCEUS. The 

 males hatch some hours or a day in advance of the females, and 

 die soon after the momentary copulation with the latter. The 

 wasps generally hatch out from the cocoons at about the same 

 time the spiders hatch from the uninfected eggs. 



Three cocoons, from four to six hours old, were placed in a 

 dish containing wasps that had hatched from other cocoons one 

 or two days previously. The female wasps walked over the 

 surface of the cocoons, continually tapping them with their 

 antennae ; most of the females oviposited into the cover of the 

 cocoons, or at least frequently projected their ovipositors into 

 them. A smaller number made their way into the interior of 

 the cocoons, taking about ten minutes to bore, mainly by rota- 

 tion of the large and sharp-rimmed head, a small circular aper- 

 ture into the cocoon. After several of the female wasps had 

 entered in this way I cautiously opened a cocoon and under the 

 compound microscope could observe the wasps piercing the 

 spider eggs with their long, needle-like ovipositors ; they seem 

 not to succeed in piercing every egg that they attempt. A 

 single wasp inoculates in this way a considerable number of 

 spider eggs. Only one wasp emerges from any one spider egg, 

 so it is probable that the wasp places only one egg in a spider 

 egg, but I hope to decide this point by a careful study of the 

 infected eggs. Rarely if ever are all the eggs in a cocoon so 

 infected ; the infected ones after three or four days turn a dull 

 brown color. If an infected cocoon is kept until hatching in a 

 closed vial, so that neither the emerging spiders nor the hatching 

 wasps can escape, the spiderlings that have escaped infection 

 ultimately catch and eat the adult wasps. 



