FAMILY ICHNEUMONIi)^. 193 



Iclineumoiiidae. 



The characters of this family, as given by Westwood, are : The abdomen is attached to 

 the hinder extremity of the thorax, and between the base of the coxa. The anterior pair 

 of wings exhibit perfect cells upon their disc. The ovipositor is straight, and often exserted. 

 Antennae setaceous or filiform, not elbowed, and composed of more than sixteen joints, 

 except in a few minute adsciti. The pupa is enclosed in a cocoon. The head is small and 

 free : eyes lateral ; mandibles slender and bidentate ; maxillary palpi five- or six-jointed, 

 pendulous : wings moderate in length and size : legs formed for running. When the 

 ovipositor is retracted, the abdomen terminates in a point. 



The larvae are parasitic upon other insects. 



Plate I. illustrates some of the characters of the family. 



The antennae are in constant vibratory motion. The insects themselves are exceedingly 

 active, and exhibit a remarkable degree of instinct in depositing their eggs where their 

 progeny will be provided for. They are very important in the economy of nature, especial- 

 ly in keeping in check other species which would be highly injurious to man. They are 

 particularly useful in reducing the numbers of the lepidoptera, scarcely a species of which 

 are exempt from the attacks of ichneumon-flies. These deposit their eggs in the back of 

 the larva, through a puncture so minute as not to interrupt its growth and perfection : 

 the larva winds itself up as usual ; but in its pupa state, the eggs of the ichneumon hatch, 

 and the progeny feed upon it : it is consequently destroyed ; and instead of the butterfly, 

 there comes forth a brood of ichneumons. Before this subject was understood , the singular 

 fact here stated was accounted for on the supposition that certain animals were susceptible 

 of transformation into others. 



The ichneumons have been divided into Ichneumones genuini and adsciti : the forewings 

 of the former have two, of the latter, one recurrent nerve. 



Ichneumon tiREViciNcroR? (Plate xxvii, fig. 10.) 



Color black. Antennae with joints twenty and more : yellowish white annulus beginning 



at about the ninth joint, and ending at the seventeenth from the base. "Wings light 



smoky brown, Scutel pale yellow : a sharp well defined ridge extends from each 



anterior angle of the scutel, to the middle of the ridge surrounding the base of the 



wing. Knees and tibia of the anterior feet rufous. 



This individual diifers from the brevicinctor described by Say, in the beginning of the 



pale annulus, which, in his account, commences at the seventeenth joint, and extends only 



to the twenty-first. The cellules of the wing agree with his figure, and also the opake 



costal spots. 



[AoEICULTlTaAL RiPORT — VoL. V.] 25 



