7890 



Insects. 



later into a pupa, in which the external divisions of the body are 

 clearly indicated. This pupa is at first of a light cheese-colour, but 

 gradually assumes the tint exhibited by the little animal on its escaping 

 from prison. Fig. 4 represents a female pupa. After having emerged 

 from the pupa state by casting a very thin enveloping skin, the perfect 

 insect, in oider to effect its escape, gnaws the round lid out of the 

 cocoon, of which we have just spoken. 



From the greater number of those cocoons which have remained hid in 

 the moss during the winter the imagos are developed, some in June and 

 some in the first half of July, so that their time of appearance coincides 

 with that of those imagos of which the larvae have fed in the spring of 

 the year, and which have only passed about a fortnight in the pupa state. 

 Fi *om those same cocoons, namely those which have remained over the 

 winter, some sawflies make their appearance in April, or even, if the 

 season be favourable, in March. When about to deposit their eggs 

 they make with their saw an incision in the side of a fully developed 

 fir leaf, extending the whole length of the leaf, and lay their eggs in 

 the opening, beginning at the base and proceeding towards the tip. 

 The number of eggs varies from two to twenty, or, according to Muller, 

 (Afterraupenfrass, 2 Auflage, Aschaffenburg 1824,), even to thirty. 

 Each egg is separately covered by a fluid ejected from the ovipositor. 

 The egg is so placed that its longer diameter is parallel with the mid- 

 rib ; the egg itself is elliptical or cylindrical, with rounded ends ; the 

 colour is yellow ; length not exceeding 1 mm. By degrees, as the 

 germ is developed within the egg, the latter swells up and the shorter 

 diameter becomes equal to the longer. In consequence of this the 

 sides of the leaf also swell up. After an interval of a fortnight or three 

 w r eeks the young larvae are born. During the first period of their 

 existence the larvae live together in companies of from fifty to eighty, 

 mostly keeping very close together and consuming the leaves at the 

 sides only. They afterwards gradually disperse and eat up the midrib 

 right down to the sheath. 



The larvae hatched in May consume last year's fir leaves during 

 May and June, spin up in the beginning of July, principally among 

 the leaves of young shoots, and generally appear as imagos in about 

 a fortnight. These again lay eggs, the larvae from which during 

 August and September live on the last year's leaves as well as on the 

 new year's, descend in the middle of September, and spin up in dark- 

 coloured cocoons among the moss and debris at or near the roots of 

 the trees. From these cocoons the imago makes its appearance in 

 the following spring. Sometimes, however, these cocoons remain 



