ICHNEUMONID FINAL INSTAR LARVAE^ — SHORT 395 



the mandible and the posterior pleurostomal process (ppp) ends in a 

 socket which receives the mandibular condyle. The hypostoma (fig. 

 1b, list) is a sclerotic band running posteriorly along the subgenal 

 margin of the cranium. Each maxilla (mx) consists of a lightly 

 sclerotized cardo (cd) and a membranous stipes (st) supported 

 ventrally by a sclerotic band called the stipital sclerite (ss(q)). The 

 medial lobe of the maxilla represents the lacinia (Ic). The galea is 

 absent. The maxillary palp (mplp) is reduced to a flattened disc. 

 A sclerotic band called the hypostomal spur (hsp) projects ventrally 

 from the hypostoma across the stipes. In many species it fits into 

 a depression in the stipital sclerite. Surrounding the posterior 

 margin of the prelabium (plb) is a labial sclerite (lbs). The labial 

 palps (Iplp) are reduced to flattened discs. The silk press (sp) at 

 the orifice (slo) of the silk glands is usually well sclerotized. Some 

 ichneumonid larvae, such as the Campopiegini, have a Y-shaped 

 sclerite, called the prelabial sclerite, on the prelabium. A sclerotic 

 band, the labral sclerite (1ms), is often present marking the dorsal 

 limits of the labrum (Im). 



The mandible (fig. Ic) consists fundamentally of a broad base (ba) 

 articulating with the pleurostomal processes, and a more slender 

 blade (bl). The base and blade of the mandible of Xorides are not 

 differentiated, but usually, as for example in the Ephialtini, the 

 blade is slender. The blade of the mandible may bear teeth (t) on 

 its dorsal and ventral surfaces. 



The antennae (ant) may be papilliform or disc-shaped. The 

 ocular lines (ol), which mark the place of the developing imaginal 

 compound eyes, are often sclerotized. 



Each spiracle (fig. Id) consists of a rounded atrium (atr) connected 

 with the closing apparatus (ca) by a length of trachea which is often 

 characteristic of the group to which the larva belongs. Finer details 

 of spiracular structure have not been used in this classification. The 

 prothoracic spiracle is usually figm-ed but, where the preparation did 

 not show the structm-e of this clearl}'^, another spiracle was selected 

 for illustration. The proportions of the structure of the spiracles are 

 relatively constant. 



The length of the setae of the skin and the presence or absence of 

 spines have been found useful taxonomic features. Spines serving as 

 holdfast organs are present on the skin of the Polysphinctini and some 

 Ephialtini. 



The drawings of heads which illustrate this paper are morphologi- 

 cally inaccurate since they show it as a flattened object, whereas it is, 

 in reality, a hemisphere. This point is important since Beirne (1941, 

 pp. 149, 167), for example, has attempted to use the position and 

 degree of curving of the hypostomal sclerite as a taxonomic character. 



