320 



AN ECONOMIC ENTOMOLOGY. 



apples and cranberries : in apples simply feeding upon the leaves 

 in a little case, but on cranberries often becoming seriously injuri- 

 ous by spinning up and eating the tips of the growing shoots. It 

 also feeds on huckleberry and allied plants, and from them goes 

 to cultivated cranberry bogs. It is there known as the ' ' fire- 

 worm," and it is distinguished from Rhopobota vacciniana, 

 another caterpillar with the same habits, by having a yellow in- 

 stead of a black head. Both these insects have similar larval 

 habits, but the Rhopobota has only two broods, and hibernates in 

 the egg stage, while the Teras has three, and hibernates as an 

 adult. There is a curious alternation of generations in this in- 

 sect, the summer broods being yellow or orange, while the moths 

 that hatch in the fall and hibernate are uniformly slate-gray. 

 Cultivated cranberry bogs are covered with water during the 

 winter, and the moths cannot hibernate on them ; so, as they lay 

 their eggs quite early in spring, if the bogs are kept covered 

 until all other vegetation has started, they oviposit elsewhere, 

 leaving the bogs free. Therefore, holding the water late, say 

 until at least the middle of May, is usually a fairly complete pro- 

 tection. The Rhopobota lays 

 its eggs upon the cranberry 

 plants late in summer. They 

 remain unaffected by the 

 water with which the bog is 

 covered until spring, then 

 hatch, and the larvae spin up 

 the tips precisely as in the case 

 of the Teras, the moths com- 

 ing to maturity early in July. 

 Eggs for a second brood are 

 then laid, and these are some- 

 times sufficient in number to 

 sweep entire bogs, giving them the appearance of having been 

 burned over, wherefore this insect has also been called * * fire- 

 worm." As against this species, late holding the water is not so 

 effectual, because it must be kept on until sufficiently warm to 

 induce the eggs to hatch, the young larvae dying as soon as they 

 break the egg-shell, or stifling before they are really born. The 

 method is feasible on a flat boQf where water can be drawn down 



Cranberry leaf with eggs of Rhopobota, and 

 a spray spun up at tip by the larva. 



