J. A. Hyslop.
Prothetely in the Elaterid Genus Melanotus.
Psyche 23(1):3-6, 1916.

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19161 Hyslop~Prothetely in the Eiderid Genus Melanotus 3 yellow band near tip; base of tarsi slightly lighter; cox= and trochanters yellowish or pinkish.
Thorax beneath pinkish; venter reddish.
First segment of beak
brownish yellow, remainder blackish.
Male, about 5 mm. in length; similar to female. PROTHETELY IN THE ELATERID GENUS MELANOTUS. BY J. A. HYSLOP,
Bureau of Entomology, Washington, D. C.
Two papers on the abnormal phenomenon termed prothetely appeared last year in PSYCHE. In one of these papers1 six biblio- graphical references were given on the subject and in the other paper2 a seventh was added to this list. Dr. Adam Boving brought another interesting paper on the same subject, published in 1914: to my attention, and in looking over the literature two more papers were 10cated.~'~
The present paper deals with a very striking case observed at the United States Entomological Laboratory in Hagerstown. The subject was Melanotus communis Gyll.
On May 18, 1915, Mr. J. J. Davis sent the writer fifty-eight living larvae of Melanotus communis Gyll., collected near Cincin- nati, Ohio, with the note that they were found damaging corn on river bottom land. These larvae were shipped in salve boxes filled with moist Sphagnum moss, and when received were isolated in similar boxes partly filled with moist earth and fed seed corn. The boxes were all placed in galvanized iron trays and the contents examined, cast skins removed, soil moistened when necessary, and new food supplied, weekly.6
Strickland7 suggested as an explanation of the phenomenon of prothetely that it "is usually caused by keeping the larvae at an abnormally high temperature." The temperature to which this particular larva was subjected could not have varied to any appre- 1 Williams, F. X., 1914, PSYCHE, Vol. XXI, p. 126. 2 Barber, H. S., 1914, PSYCHE. Vol. XXI, p. 190. Kemner, A., 1914, Ent. Tidsk. (Swedish), Vol. XXV, pt. 1-2, pp. 87-95. Tragardh, I., 1912, Fauna och Flora, pp. 245-255. 6 Peyerimhoff, P. de, 1911, Bull. Soc. Ent. France, p. 327. 6 The writer was ably assisted in this work by Messrs. H. L. Parker and W. E. Pennington of the Station staff.
2 Strickland, E. H., 1911, Biol. Bull., Vol. 21, pp. 313-327.



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4 Psyche [February
ciable extent from that of the fifty-seven other larvae of the same series in the same trays. Up to the date of writing, September 23, 1915, three adults have emerged from this material, all of which appear to be perfectly normal, only seven of the larvae have died and the remainder are moulting normally and feeding freely. In this same type of cage and in the same insectary, we have been carrying on experiments with about 2,000 Elaterid larvae from all parts of the United States and the West Indies. However, this is the only instance of prothetely that we have ever observed. The soil with which these cages are filled is all Fig. 1. Plotted curve of Melanotus molting periods. Cross indicates point at which pro- thetelous larva appeared.
The dotted lines connect actual record points. taken from one potting bench. The amount and kind of food, I believe, can be eliminated as a factor in this particular instance as our larvae are always supplied with an excess of food. The lids of the boxes, which we use as cages, fit with varying degrees of tight- ness and the rate of evaporation is, therefore, very inconstant in any given series of cages. On account of this, the cages are only watered when, in the judgment of the examiner, it is necessary. This introduces a large personal factor and could easily result in a cage becoming much more dry or moist than the other cages of the same series. As this seems to be the only variable, 1 am inclined



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innal and pmthetehs larva and normal pupa of Mclanofaw cmmunis, Fig. 1, dormre of normal t.
Fig, 2, vmiron of pupa. Fig. 3, dorsum of prothetelous larva. Fig. 4, veatron of pmthetelous i. Fig. 6, lateral aspect of prothetelous larva.



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PSYCHE, 1916.
VOL. XXIII, PLATE 111.
Mehnotus communis normal and prothetelous larva. Fig. 1, dorsum of the head of pro-
thetelous larva.
Fig. 2, prosternum of normal larva.
Fig. 3, 9th and 10th abdominal seg-
ments of prothetelous larva.
Fig. 4, dorsum of head of normal larva. Fig. 5, prosternum of prothetelous larva.




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19161 Hyslop-Prothetely in the Elaterid Genus Melanotus 5 to believe that an abnormal humidity factor at or shortly before the time of pupation is the causative stimulus of this phenomenon. The accompanying plotted curve (Fig. 1) indicates the period in the activity of the series, when the individual in question transformed to the abnormality herein described. The cages had all been examined on September 3. In examining the cages September 8, the prothetelous larva was discovered. This was a period of minimum moulting immediately preceding a very abrupt and extensive moulting period. The moulted skin of this larva was perfectly normal in every respect and, by careful com- parative measurements, was found to be very nearly identical with the last larval skin; that is, the skin shed when a pupa is formed under normal conditions. The table (Fig. 2) shows the measure- Fig. 2.
Table showing comparative measurements of larval skins of penulti- mate instar, ultimate instar and prothetelous larvae. Length of dorsum of 9th abdominal segment . . Width of dorsum of 9th abdominal segment.. Length of dorsum of 1st thoracic segment. . . ments of this cast skin as compared with a larval skin from the ulti- mate and penultimate instar.
This prothetelous larva is (Plate 11, Figs. 3, 4, and 5) predomi- nantly larviform. The abdomen is typically so and normally chitinized, with the exception of a pair of membranous papilliform areas on the posterior margin of each sternite except the ninth (Plate 111, Fig. 3). The thoracic sterna are membranous except a triangular area on the prosternum (Plate 111, Fig. 5), which is nor- mally chitinized. The membranous areas are decidedly protuberant. The cox= and trochanters are larviform with typical pupiform femora, tibiae and tarsi. The ventral part of the protergite is membranous and very much expanded posteriorly. A pair of
anterior and a pair of posterior papillae are borne on the spiracular 2.782
1.979
1 ,498
3.103
2.193
1.819
3.156
2.193
1.712




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