370 THE CANADIAN ENTOMOLOGIST 



cocoon. The great majority of the larvae of the saw-flies form 

 cocoons just beneath the surface of the ground or among the debris 

 on its surface, as the lophyrids, dolerids, phyllotomids, tenthre- 

 dinids, holocampids, acordulecerids, hylatomids, and most nematids. 

 Some individuals of the first brood of the lophyrids attach their 

 cocoons to the leaves of the host plants. The cocoons of the 

 acordulecerids are white and compact; those of the hylatomids 

 large, white and lace-like; while in all the others the cocoons are 

 dense and black or brownish in colour. 



In most insects, when the cocoon has been formed by the larva,, 

 it transforms almost immediately to a pupa — at least, within a 

 week or two. A different condition is found among the larvae of 

 the saw-flies. Some of the species are, so far as known, always 

 single brooded; the larvae of such species emerge early in June, 

 complete feeding in a few weeks, enter the ground or rotten wood, 

 form their cocoons or cells, but live as larvae withm them until the 

 following spring, when they transform to pupae, and emerge as 

 adults in May or June. A similar condition is found in those 

 species that are apparently more than one-brooded, the ultimate 

 larval stage is long and the pupal stage short. Writers frequently 

 refer to the time when the larvae form their cocoons or enter the 

 ground as the beginning of the pupal stage. Such a designation is 

 clearly incorrect. 



Any statement as to the number of broods of any given species 

 of saw-fly should be made with reservation. Many insects, prob- 

 ably a large majority, appear at a definite, stated time, usually not 

 exceeding a period of two or three weeks and sometimes less. 

 Such a condition does not exist in this group, for adults may appear 

 over a period of four to eight weeks, so that it is possible to find on 

 the same host plant and even on the same leaf, if the plant be one 

 that has large leaves as a dock (Rumex) larvae that are fully grown, 

 others that have just emerged from the egg, and various sizes be- 

 tween these. Such a condition in June would probably mean that 

 they were larvae from the eggs of females produced from w^intering 

 larvce, but in July the young larvae may have been produced from 

 the eggs of females that have matured the same season or from 

 females produced from wintering larvae that have been very slow 

 in development. The field conditions would warrant considering. 



