ORDER HYMENOPTERA 229 



but several species as ebenus and privatvs and the European 

 glomerata are known as pests feeding externally upon the 

 leaves of potato and rose. 



According to Konow (1805) there are twenty-one de- 

 scribed species of Schizocerus which are distributed as 

 follows: four European, ten North American and eight 

 £outh American species. With the addition of one species, 

 S. zabriskei (see pi. 3) not listed by Konow, we can increase 

 the number to twenty-two. 



For our knowledge of the habits of the leaf-mining species 

 of Schizocerus, we must rely chiefly upon Dyar, who has 

 published several short papers upon this group. 



According to Dyar (1897) S. prunivorus lays its eggs in a 

 pyriform slit under the lower epidermis at the middle of one 

 edge of the leaf. The larva hatches and eats a curious 

 winding slit down into the leaf, later this reaches the edge. 

 The larva drops to the ground, where it makes a cocoon of 

 yellowish silk. Five instars are described. 



Dyar (1893) describes the habits of S. tristis fumipennis 

 a feeder of Hosackia quadriflora but does not state whether 

 it mines. The cocoon is found on the back of the leaf. It 

 is oblong rounded and composed of coarse silk of irregular 

 texture and not compact enough to be opaque. 



In 1900 Dyar described briefly the life history of S. za- 

 briskei. The species is of special interest because it is one 

 of the few Hymenoptera which leave one leaf, when the food 

 is exhausted and start a fresh mine in another. Webster 

 (1900) has described the species is more detail from whom 

 we quote: 



The eggs are deposited in the edge of the leaves, deposition 

 usually being completed in ten to fifteen seconds. As soon 

 as hatched the larvae begin to feed on the leaf, and ultimately 

 mine out the greater part of the pulpy substance, but never eat 

 through the surface until driven to do so from lack of food, whence 

 they emerge and make their way to a fresh leaf, immediately enter 



