RILEY — LARVAL HABITS OF BLISTER-BEETLES. 55 I 



the unicoloroHS form oi Epicaiita cinerea (Forster), or the Mar- 

 gine Blister-beetle*; Xho. Epicauta pennsylvanica (DeGeer),|or 

 the Black Blister-beetle ; the Alacrobasis unicolor (Kirby),J or the 

 Ash-gray Blister-beetle ; and the form of it described as murina 

 by LeConte, or the Black-rat Blister-beetle, 



Since then I have found it very easy to trace the larval habits 

 and development of the two more common potato-feeding spe- 

 cies around St. Louis, viz. the Striped Blister-beetle {Epicauta 

 vittata^ Fabr.)§ and the Margined Blister-beetle {marginata 

 Fabr.) just alluded to. 



Careful examination of locust eggs in the vicinity of potato 

 fields frequented by these beetles show a varying proportion of the 

 egg-pods aftected, and in some locations nearly every pod of the 

 Difterential Locust ( Caloptenus differentialis) will contain the 

 Epicauta larva. The eggs of this locust are laid in large masses 

 Fig. 39. ^^^ of 70 to about 



100. The pod is 

 but slightly bent, 

 rather compact 

 outside, while the 



Caloptenus differentialis. SggS are irregu- 



larly arranged, and capped with but a shallow covering of mucous 

 matter. It is the egg-pod of this species which the larva of the 

 two Blister-beetles in question prefer ; for while they will feed 

 upon those of other species in confinement, I have so far found 



* The black, gray-margined form, very appropriately described by Fabricius as margi. 

 nata, is referred to cinerea Forster by modern systematists, and specifically united with it 

 by Dr. Horn. Yet the fact remains that the two are not ordinarily, if ever, found com. 

 mingled. The margined form is very common in potato fields in Missouri, It shows little 

 variation and is found almost invariably in conjunction with vittata, but not with the uni- 

 colorous form in question, which is most common farther west and occurs abundantly with- 

 out the margined form— all which is against the specific union of the two. 



f -^atrata Fabr, 



J :=cinerea Fabr., Fabricii Lee, murina Ltc, debilis Lee. I accept Dr. Horn's conclu- 

 sion that the last two are but poorly developed forms of this species. Yet the murina foim 

 is not due to rubbing or injury, but issues from the pupa without a trace of gray scales on 

 the elytra. 



§ =zlemniscata Fabr. Dr. Horn retains lemniscala as a distinct species in his Revi- 

 sion already referred to, 1 he outer stripe in the bi-vittate specimens divides up in others 

 so as to give the tri-vittate character on which lemniscala is founded. Both extremes and 

 every possible variation between them occur constantly together in the same potato field in 

 Missouri, and there are no other differences of specific value. 



