432 



AN INTRODUCTION TO ENTOMOLOGY 



g. 502. — Gall of Adelges 

 pinifolicB on spruce. 



protected by the remains of the body and closed wings of the dead 

 insect. 



It has been determined that these plant- 

 lice infesting the pine leaves are specifically 

 identical with those that issue from a cone- 

 like gall found on several species of spruce 

 (Fig. 502). The spruce-inhabiting form has 

 been known as Chermes abieticolens; but 

 -piniJolicB is the older specific namo and 

 should be used for all forms of this species. 

 It is probable that this species has a two- 

 year life-cycle and that spruce is its primary 

 host and pine its secondary host. 



The green-winged adelges, Adelges ahle- 

 tis. — This species causes the growth of pine- 

 apple-shaped galls on several species of 

 spruce (Fig. 503). It is a European species 



and its life-history has been the subject of m.uch controversy. It is 

 held by Borner ('08) that it has a typical life-cycle in which there are 

 two parallel series: first, an annual series on spruce alone; and 

 second, a two-year series in which larch is 

 used as a secondary host. On the other 

 hand, Cholodkovsky ('15) maintains that it 

 is a parthenogenetic species; that its life- 

 cycle includes only two generations, the 

 agamic hibernating stem-mothers and the 

 gallicolae; and that the form with a typical 

 life-cycle is a distinct species {Chermes 

 viridis). Dr. Patch ('09) has studied Adel- 

 ges abietis in Maine and has found only the 

 parthenogenetic forms, the hibernating stem- 

 mothers and the gallicolse; thus confirming 

 the conclusion that it may have become a 

 parthenogenetic species. 



The pine-bark adelges, Adelges pinicorti- 

 cis. — This species infests several species of 

 pine, but especially white pine. The trunks 

 and larger limbs of the infested trees often 

 -Gall of Adelges ^PPff^ ^^ '^ whitewashed; this is due to the 

 woolly excretion which covers the bodies 01 

 the insects. But little is known regarding the 

 life-cycle of the species. Wingless females, which are doubtless agamic 

 as they lay many eggs, hibernate on the pine and feed on the bark 

 in the spring. They lay their eggs in April; these soon hatch and the 

 young develop into winged agamic females in May. These soon dis- 

 appear and the pine is said to be free from the pest during the simimer. 

 Return migrants to the pine have not been observed; but there 

 must be a generation of these, the parents of the wingless hibernating 



Fig. 503-- 

 ahietis. 



