THE AMERICAN ENTOMOLOGIST. 



"5 



THE ROSE-SLUG. 



(Sc/aitJria rosu Harris.) 



The main points in the history of tliis 

 well-known garden pest are given by Harris 

 in his "Insects Injurious to Vegetation," 

 etc. It undoubtedly originated in New 

 England, probably upon Rosa lucida or R. 

 blanda, as these are the species of wild 

 Rose upon which it preferably feeds. Dr. 

 Harris first observed it in the gardens of 

 Cambridge, Mass., in 1831, and mentions 

 that it was six or seven years before it 

 made its appearance in Milton, where he 

 then resided. So far as can be ascertained 



[Fig. 42.] 



Selandria kos.k : (i, egg, natural size; /', do. enlarged ; c, 

 slug and its work, natural size, ; </, do. enlarged (after Riley). 



it is not indigenous to any of the States 

 west of the Alleghanies. It has, however, 

 been abundantly disseminated over these 

 States by means of rose bushes imported 

 from eastern nurseries. As it spreads very 

 slowly on the tvitig, had our nurserymen 

 and florists understood its habits and taken 

 the precautions which such knowledge 

 would have suggested, our western gardens 

 might long have enjoyed immunity from 

 its ravages. 



Since Harris's descriptions may not be 

 accessible to all our readers we will briefly 

 recapitulate the more important facts. The 

 small, sluggish, black flies (Fig. 43, a) emerge 

 from the ground about the time that the roses 

 are in full leaf, and within a few days there- 

 after begin depositing their eggs. The pro- 

 cess of oviposition and the appearance of 

 the newly-hatched slug are thus described 

 byMiss M. E. Murtfeldt in an article con- 

 tributed to the November number of the 



Gardeners' Monthly: — "With their saw- 

 like ovipositors the female flies pierce the 

 edges of the leaves and force their eggs 

 singly, towards tlie tip of the serrations, 

 beneath the cuticle on the under surface. 

 The egg is circular, about one-twentieth of 

 an inch in diameter, and so flat at first as 

 to be imperceptible except upon the closest 

 scrutiny. It hatches in eight or ten days, 

 and, before the larva escapes, swells con- 

 siderably, appearing like a minute blister 

 on the under side of the leaf, within which 

 the coiled embryo is distinctly visible. 

 The young slug upon emerging is one- 

 tenth of an inch in length and of the 

 diameter of No. 30 spool cotton — the 

 round, tawny-yellow head being the broad- 

 est part. The color is greenish-white with 

 a dark green vesicular line as soon as it 

 begins to feed." 



It feeds only at night, except in very 

 cloudy weather, and exclusively upon the 

 upper surface of the leaf, from which it 

 gnaws the parenchyma, leaving the veins 

 intact. During the day it rests motionless 

 on the under side, of the leaf. 



The larval life of this insect extends 

 over a period of fourteen or fifteen days, 

 during which it molts four times. The full- 



Selandria ros.b : — i?, female fly; />, her sav 

 tenna — enlarged (after Riley). 



grown slug is rather more than one-third 

 of an inch in length, by one-ninth in 

 diameter. The thoracic joints are some- 

 what swollen and humped, but not puffed 

 out laterally, as in some closely allied 

 species, nor has it, like these, a slimy sur- 

 face. The color is a translucent dull 

 yellow, becoming more opaque at the last 

 molt. Soon after this it enters the ground, 

 and incloses itself in a fragile, earthen 

 cocoon, within which it remains dormant 



