58 THE REPORT OF THE No. 36 



The eggs are always laid by the female within the tissue of the host plant. 

 Where the larvsB are borers, Xiphydriidae, Siricidae, Cephidae, and Oryssidas, they 

 are laid in holes bored in the stems of bushy plants or in the limbs or trunks of 

 living or recently dead trees. Where the larvae are leaf-feeders, the eggs are 

 placed in slits sawed by the female from the under surface and located between 

 the two layers of parenchyma. A few species insert their eggs in the petiole of 

 the leaf, some of the gall-making species in the leaf-buds, and Hoplocampa 

 cookei in the blossoms of cherry on the sepals or the upper part of the calyx cup. 

 The eggs are oval in outline, flattened, usually white in color, though sometimes 

 bluish or greenish, and very difficult to locate when first laid. They swell after 

 a short time, varying with the species, to twice their original size and push out 

 the surface of the leaf so that it appears to be covered with little mounds. The 

 end of the egg may project from the slit at this time. The cause of the swelling 

 is unknown. 



The number of eggs laid in a single leaf varies greatly. A large majority 

 of the species distribute their eggs over the adjacent leaves of the host plant, one 

 or two in a leaf, and some, if one may judge from the distribution of the larvae 

 collected, on widely separated bushes. Some species on the other hand lay a 

 large number of eggs within the same leaf, as in the case of Macremphytus 

 varians, thirty or forty, distributing them generally over the under surface, while 

 in Pteronus fulvicrus there are usually about twenty placed in a group at the 

 extreme tip of the leaf. 



The eggs are usually located along the larger veins, as in Pteronus ribesii 

 or along the margin of the leaf. In Macremphytus they are placed near the 

 secondary veins, but in Pteronus fulvicrus, Cimhex, Trichiosorna, and many of 

 the species whose larvge are leaf-miners, the veins are disregarded. From twelve 

 days to three weeks are required to complete the embryonic life. The young larvae 

 issue through the slit made in the leaf by the female in inserting the egg. 



The length of the feeding time of the larval life varies considerably with the 

 species. There are five to seven instars, the number being different in the different 

 groups, which usually require about fifteen days, sometimes as few as twelve in 

 some species, and as many as twenty or even miore in others. 



Each species is quite constant in its method of feeding; that is, whether the 

 larvae feed singly, solitaire, ui a number together, gregarious. The way in which 

 the eggs are placed by the female has much to do with this. In no species where 

 the eggs are well distributed has it been noted that the larvae were other tlian 

 solitary feeders, but in Macremphytus, where many eggs are laid in a group, the 

 larvae feed gregariously for the first half of their life and solitary for the last half, 

 while in Pteronus fulvicrus, where the eggs are also laid in a group, the larvce 

 are gregarious throughout their feeding period. An apparent exception is found 

 in the case of the larvae of the Lophyrinae, where a number of eggs are placed 

 in the needles at the apex of a single branch and the larvae become gregarious 

 through the consumption of the adjacent needles. 



The manner of feeding is strikingly varied. In many nematids and hoplo- 

 campids, the young larvae as soon as they emerge from the egg eat holes through 

 the leaf and continue feeding around the circumference of the hole, clinging to 

 the leaf with their thoracic legs and holding the body S-shaped in the hole. When 

 a number of eggs are placed adjacent to each other, the larvae continue this method, 

 feeding until this portion of the leaf is devoured, and then they migrate to another 

 part of the leaf or an adjacent leaf and are edge feeders for the remainder of 



