THE LIFE HISTORY OF HEMEROBIUS STIGMA, STEPH. ( .) ( .) 



It is impossible to give, in a brief note such as this, sufficient 

 details to distinguish the larva of H. stigma from that of other 

 species. The present description would answer almost as well for 

 larvae of such distinct species as H. humuli and H. lutescens ; but 

 •of course these larvae are rarely found on pines. Colour in Hemerobiid 

 larvae is extremely variable, being due largely to the colour of 

 internal organs. 



During the greater part of the year larvae may be found on 

 pines, where they feed on aphids, leaf hoppers, and mites, piercing 

 these with their jaws and sucking out the juices. The larva rims 

 •actively with a slight side-to-side motion of the head, the tip of 

 abdomen being used as an additional leg. When at rest it has a 

 habit of lying stretched out along a needle with its head towards 

 the base. The period of larval life varies from 22 to 28 days with 

 with an average temperature of 65° F., or 46 to 50 days with a 

 temperature averaging 50° F. When full fed a crevice in the 

 bark or between two needles is sought out and here a loose cocoon 

 ■of silk is spun, the anal extremity being used as a spinneret. 



The cocoon, as in other Hemerobiids, is quite a loose structure 

 of elongate oval shape. In from eight to ten days after spinning 

 the pupa is disclosed. This is at first of a yellowish colour, the eyes 

 and back being brown. All the characters of the adult are now 

 visible, the legs held close together ventrally, the wing rudiments 

 at the sides and the antennae lying over these and curling ventrally. 

 In from one and a half to three weeks, according to temperature, 

 the pupa has darkened wholly to a deep brown colour, and from 

 now onwards the imago may emerge any day. In summer emergence 

 takes place very shortly after this darkening, but in cold weather 

 the pupa may rest for weeks in this condition or may even pass 

 the winter as such. This is, in fact, the stage in which the coldest 

 weather is passed, but a warm spell even in December or January 

 will cause the appearance of the adult fly. 



The pupa struggles for a time within its cocoon, the legs and 

 antennae being now free, then tearing an irregular hole with its 

 mandibles, it emerges and crawls on to a suitable support. Here 

 the pupal skin is cast and the insect commences adult life. Pairing 

 takes place in a day or so, usually at night, the insects being of 

 nocturnal habits mainly. 



Eggs may be laid directly they mature, but in winter only on 

 warm days ; these then hatch according to the prevalent tempera- 

 ture, as has been shown. 



We see then that this species is really on the wing all the vear 

 round in a normal season. At no period have I found its I dim I com- 

 pletely absent, species of Lachnus and Eulachnus, besides various 

 Psocids, being always procurable, even in the hardest of winters. 



