LIGHT-GUYING COLEOPTEROUS LARVA. 



in the principal characters which I have here described from my lu- 

 minous larva. As the only luminous insects which occur in this 

 country belong to the Pyrophori and Lampyridce, I feel tolerably 

 certain that this larva belongs to Pyrophorus, because the larvae of 

 Lampyridce have a broader, softer, and natter body, and their 

 oral parts must be smaller, at least in those of this country, none 

 of which exceeds an inch in length. But the largest Pyro- 

 phorus from the Argentine Kepublic (P. punctatissimus, Bl. Can- 

 deze, Monog. iv. p. 17) is \\ inch long, and bears the same pro- 

 portion to my larva that the large larva of Agrypnus fuscipes, 

 described by Lequin, bears to the imago -state of Antliia sex- 

 guttata, (Gruerin, Mag. de Zool. 1832, ix. 41). Indeed this 

 larva has many points of resemblance to the larva here described ; 

 but it belongs to another group of the Elateridce, in which the 

 larva has the anal tube retracted and covered by the preceding 

 elongated segment, which bears the form of a strong denticu- 

 lated horny fork. 



My larva agrees with others of the same family in the project- 

 ing anal tube and the unarmed preceding segment, like that of 

 JEl. sanguineus. Erichson mentions a larva of Pyrophorus from 

 Cuba(Wiegmann's Archiv, 1841, torn. i. p. 87), and says that the 

 body is softer, more fleshy, and the segments are more separated 

 — characters which agree very well with the construction of my 

 larva ; but he also mentions that the last segment bears many 

 small humps, which I certainly did not notice in my specimen. 

 This may, indeed, be a specific character, and not a generic one. 



The conclusion at which I have arrived is therefore this — 

 that the luminous larva observed by Azara, Ogilvie, and myself 

 is that of Pyrophorus punctatissimus . 



With reference to Mr. Murray's Astraptor illuminator, it ap- 

 pears to me not to be a larva of one of the Elateridce, but rather 

 to be that of one of the Lampyridce. The figure given of the 

 mouth shows none of the characters of a larva of Elateridce, but 

 agrees far better with the structure of the larva of the Lam- 

 pyridce. This view is also supported by the retracted head, the 

 depressed form of the body, the sharp lateral margin, and the 

 distinctly separated segments, which form, on each, projecting 

 angles before the union with the adjoining segment ; all these 

 are characters distinctive of the Lampyridce larvae. 

 Buenos Ay res, April 25, 1871. 



LINN. JOURN. — ZOOLOGY, VOL. XI. 



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