Rhynehart — Life- History and Bionomies of the Flax Flea-Beetle. 50?' 



Seedlings of various weeds were raised in pots, and a number of adults caged 

 on each species of weed, no other food being supplied. The following weeds 

 were used: — Spurrey (Spergida arvensis), Daisy {Bellis perennis), Dock 

 {Bumex sp.), cut-leaved G-eranium (Geranium dissechim), Groosefoot {Cheno- 

 ■podiuni album), Charlock {Sinapis arvensis), and Redshank [Polygonum 

 Persicaria). In all cases the seedlings remained free from attacl<, the beetles 

 showing no attempt to feed on them. In the field, observations were made 

 to detect, if possible, weeds eaten by the beetles, but no definite instance of 

 such could be seen. 



Eecords of food plants in the writings of other workers are singularly 

 rare, and, beyond these from flax in Ireland, there. is little definite informa- 

 tion to be found. Allard, according to Fowler and other writers, states it 

 is commonly found on the Hornbeam {Uarpinus Bdulus) in woods ; but that 

 it actually feeds thereon is doubted by some authorities. The present writer 

 has not had an opportunity of making observations regarding this possible 

 food plant. "On low plants" is the general habitat given by Fowler (24), 

 whilst the original description gives the " habitat in pratis ad fossas in 

 Westrogothia Dom. Gyllenhal " (49), but mentions no food plant. 



8. — JSTature of Damage. 



(ffl) By the Adult. — The principal damage is caused to the flax in its 

 seedling stage, and by the adult insect. The cotyledons of the seedlings are 

 the parts first attacked, with the result that they become perforated and 

 notched, as shown in PL XV, figs. 1, 2, 3. If the attack is severe, the entire 

 cotyledons and the terminal bud between them may be devoured, in which 

 case the seedling succumbs. 



When this is not the case, and when the terminal bud proceeds to give 

 rise to young foliage leaves, the beetles leave the cotyledons and begin to 

 devour these tender leaves. Even at this stage the severity of attack may 

 increase, so that the young plant becomes entirely destroyed. 



It frequently happens, however, that the attacked seedling goes on 

 growing and ultimately produces a plant. Nevertheless, the injury done to 

 the terminal bud of the seedling induces the development of lateral buds in 

 the axils of the foliage leaves which would otherwise remain dormant, hence 

 flax plants which in their early days have been attacked by the flea-beetle 

 are frequently bi-anched, but such induced branching must not be confused 

 with the normal branching which is found in some strains of cultivated flax. 



It is noticeable that the beetles always prefer the newly developed foliage 

 leaves ; and at a given time they are nearly all to be found in relatively the 



