F. X. Williams.
Prothetely in the Larva of Photuris pennsylvanica De Geer.
Psyche 21:126-128, 1914.

Full text (searchable PDF, 788K)
Durable link: http://psyche.entclub.org/21/21-126.html

The following unprocessed text is extracted from the PDF file, and is likely to be both incomplete and full of errors. Please consult the PDF file for the complete article.

.
126 Psyche ]August
Trigonornetopus vittatus Loew.
A single specimen before me, taken by Mrs. A. T. Slosson at Biscayne Bay, Florida, agrees with Loew's description in most particulars. The wing coloration indicated by Loew is like that of the species just described. In the present specimen the differ- ence between the yellowish anterior portion of the wing and the smoky posterior portion is but weakly indicated; the dark shade appears to begin behind the third vein, instead of in front of it, thus leaving a pale streak along the anterior margin of the first posterior cell. No trace of the distal extension of the dark shade to the costa at the tip of the second vein, as indicated by Loew, is perceptible, nor is there any strong contrast in the coloration of the veins in the two regions. Another difference occurs in the coloration of the abdomen; this may, however, be due largely to the condition of the specimens, since the insect is said to have an entirely pale abdomen in life. In Loew's specimen the abdominal segments are said to have basal dark bands, while in the specimen before me these bands are apical. It is possible that the Florida specimen represents a distinct species, but the variability shown by the three specimens of J'. albifrons, and the paucity of material, indicate a conservative course.
PROTHETELY IN THE LARVA OF PHOTURIS PENNSYL- ViANICA DE GEER.
BY FRANCIS X. WILLIAMS,
Bussey Institution, Harvard University.
The term prothetely (irpoOelv, to run before, and r&Xo s, con~pletion) was proposed by Kolbe in 1903, who applied it to that condition found in insect larvae in which the imaginal discs have developed with abnormal rapidity resulting in the production of larvae with pupal or imaginal characters. Prothetely, though not of common occurrence, has been noted chiefly in coleopterous larvae, being there represented by external wing-pads, adult legs, additional antenna1 joints, modified mouth- parts, abdominal tergites, etc., one or several of these peculiarities occurring in a single larva.




================================================================================

In the fall of 1913, the writer collected upwards of one hundred larvae of our common large firefly, Phoiuris pennsylvunica DeG., in the Arnold Arboretum, adjoining the grounds of the Bussey Institution, These larvse, ranging from about 13 to 18 mm. long, were in the second and last year of their growth. Under natural conditions they should have pupated in May or June of 1914, and produced adults a few days later, but, owing to the fact that they were kept under artificial conditions, adults emerged in late winter as well as in summer.
Kg. 1.
Prothetelous larva of Photuria peltnsyZmniea De Geer. 1, dorsal view; 2, ventral view.
As secured in the field, these larvae appeared to be perfectly normal.
They were examined from time to time in the laboratory, and on May 27, 1914, an individual was found with a pair of well developed wing-pads on the meso- and metattiorax. Two days later another such larva was discovered. Photographs were taken showing the dorsal and ventral view of one of these larvae ansesthe- tized with chloroform, and are reproduced above. It will be seen that the wing-buds are here much smaller than the wing-cases of



================================================================================

128 , Psyche [August
a pupa, but similarly situated; they are quite symmetrical and are developed just under the heavily-chitinized tergites which they reflex a little. The buds of the metathorax representing the wings are slightly larger than the elytral buds; in one specimen they are almost entirely covered with brown chitin, in the other the buds of the metathorax are largely of a whitish color and their bases show through the tergite as white subcircular areas. . Prothetely has been noted by a number of observers : Heymons (1896)l found it in the larva of Tenebrio molitor; Busck (1897)2 observed it in six larvae of Anthrenus varius; Riley (1908)3 speaks of a prothetelous larva of a pyrochroid beetle, Dendroides canadensis. In lepidopterous larvae Hagen (1872)4 and others mention the silk- worm, Bombyx mori, and Kolbe (1903)5 the Lasiocampid, Den- drolimus pini.
As aforesaid, prothetely appears to occur most frequently in the Coleoptera, and Riley offers as an explanation of this, the fact that the wing rudiment in most coleopterous larvae is according to Tower 'not sharply marked off from the body hypodermis and is usually directly evaginated to form the imaginal organ.' The step from this condition to an external wing-pad would be com- paratively simple, which would not be the case in the Lepidoptera and the Diptera for example, for here the wing rudiment is well differentiated from the body hypodermis, for the former is in- vaginated and thus lies in the body cavity, a condition designated by Tower as the "enclosed type" of wing development. Inasmuch as all the cases of prothetely noted occur only in larvse kept under artificial conditions, this accelerated develop- ment is probably due in some way to these unnatural conditions. Strickland (1911)6, is of the opinion that prothetely "is usually caused by keeping larvae at an abnormally high temperature. This probably results in an increased supply of the enzymes which cause these histoblasts to develop. "
Neither larva of Photuris pennsylvanica pupated; they lagged behind the other larvae, being, so to speak, already partly in the 1 Heymons, R., 1896, Sitzungber. d. Ges. nat. Fr. Berlin, pp. 142-144. ZBusck, Aug., 1897, Proc. Ent. Soc. Wash., W, p. 123. sRiley, Wm. A., 1908, Ent. News, XIX, pp. 136-139. <Hagen, H. A., 1872, Stettin. ent. Ztg., pp. 392-393. 'Kolbe, H. J., 1903, Allgem. Zeitsch. fur Ent., Bull. 8, No. l', p. 28. 6Strick!and, E. H., 1911, Biol. Bull., XXI, pp. 313-327.



================================================================================