Laphria thoracica Fabricius: Larval and Pupal Descriptions

Greene, C. T. 1918. A contribution to the biology of N. A. Diptera. Proceedings of the Entomological Society of Washington Vol. 19, Pages 146-161, Plates 17-20 (Dasyllis thoracica Pages 146, 149-152, 157, Plate XVIII (Page 159)).

[Introductory remarks on p. 146]

The Diptera discussed in this paper was reared by the writer at the Eastern Field Station, Falls Church, Va. All the species discussed below remain in the larval stage during the winter. The larva of and Dasyllis thoracica are predaceous on Coleopterpus larvae, therefore they are of importance. The larva of Dasyllis is a secondary wood-borer in addition to being predatory. All of the above species are known in the adult stage but their seasonal history and habits are entirely new.

[Description begining on p. 149]

Dasyllis thoracica Fabr.

Syst. Antl., p. 158

This species is predaceous in the larval stage and a secondary wood-borer, in moist dead, Tulip stumps. It closely resembles a Coleopterous larva and is easily overlooked because it closely resembles the wood fibre, in which it lives. The larvae were collected at Falls Church, Va., April 10, 1914, by Mr. S. A. Rohwer and the writer.

They pupated April 21, 1914 and emerged May 11, 1914. Under natural conditions, the larva pupates in the gallery, and the pupa is fairly active.

Larva (plate XVIII, fig. 1).

Larva.--Opaque, white, elongate and cylindrical. The entire larva longitudinally striate. The greatest width of the larva is across the second segment; other segments nearly parallel: The larva is 27 mm. long and 5.5 mm. wide across the second segment, while the other segments are nearly 5 mm. wide.

The head is very heavily chitinized and black with the basal corners reddish. From a dorsal view the head is divided into three parts. The [p. 150] basal part reaches the full width of the head; it is deeply concave on the apical edge, in the middle of which is a long, slender, tooth-like projection extending up between the two upper sections. Each of these sections are somewhat triangular in shape; the inner side terminates into a tooth-like projection at the apex and below this, on the outer edge, is a similar projection. The antennae are located near the basal outer edge of this last mentioned projection. The antennae have two cylindrical joints of nearly equal length, the first joint is reddish-brown at the base and yellowish at the apex, while the coloring of the second joint is the reverse. All the bristles of the head are pale yellow.

For details of the head see drawing, fig. 5 dorsal view and fig. 4, ventral view.

First segment rather broad and rounded. At the apex is an elliptical area finely granulated, being much finer at the base. Just below this is a perfectly smooth, narrow, transverse band, not quite reaching the lateral edges. The second segment is about half the width of the first, along the apical edge is a narrow transverse space which is very finely rugose. The third segment is very narrow, being about half the width of the second segment. Near the apical edge are two rather sharp transcerse wrinkles slightly depressed or flattened in the middle. Segments four to ten are about the same width. Segments four to nine, each have one pair of ampullae on the dorsum and two pairs on the ventral side. The last segment is deeply depressed on the basal half, faintly rugose and with two well defined longitudinal ridges on the lateral edge. Towards each outer edge is a large spiracle, dark, yellowish-brown and rather heavily chitinized. For further details see figure 1. The apical half of this segment is raised much higher than the basal half, slighly rugose and terminates into a broad and narrow, reddish, chitinous plate, black on the outer edge, in the center of which is a prominent, black, tooth-like projection. This chitinous plate has a large, yellowish bristle extending from the underside near both of the outer corners. Near the middle of the last segment, on the elevated portion, are four large yellowish bristles, in a transverse row.

The details of the under side of the head can best be seen in the drawing, figure 4. All the dark portion is heavily chitinized and black, the dark area in the central basal part is reddish on the apical edge. The bristles are yellowish.

On the apical edge of the ventral side of the first segment is a narrow cresent-shaped area finely granular. Segments one to nine each have a yellow bristle, near the middle and out near the lateral edge.

At the apex of the last segment, on the ventral side, near each outer basal corner is a yellow bristle. At the base of this segment are several, short, well marked ridges.

On the side of the first segment, near the base is a spiracle, nearly circular having three faint ridges on the cephalic side, just below these is an opening which is pit-like in appearance. It is dark brown, chitinous and fairly granular, located in a small depression in the larva. For details see drawing, figure a.

[p. 151]

On the side of segments three to nine, and located at about the apical tird, is a small, round, flattened spiracle, with one faint slit across the middle.

The PREPUPAL larva is white and about the same size and appearance as the larva. There is a great shrinkage of the first segment and from a side view the dorsum of this segment is concave.

The humeral spiracle is formed slightly in front of and above the large anterior spiracle of the larva, and all the lateral, abdominal spiracles are formed in front of and below those of the larva. All the abdominal spines and bristles are pale yellow and perfectly formed under and show through the semi-transparent larval skin. The large pointed horn-like projections at the apex of the abdomen project slightly through the skin and are of the darkened, nearly normal coloring.

Pupa (plate XVIII, fig. 2).

The pupa is elongate, cylindrical, moderately shiny and faintly rugose. The general color is pale yellow ochre. It measures 20 mm. in length and 5 mm. in width at the thorax while the abdomen is slightly narrower.

Head.--On each side of the apex is a large, pointed horn-like projection, below each of these, on the side, is a larger one with three large prongs, the last one having two small points at the apex.

These large projections are deep reddish-brown, very rugose at the base and smooth and shiny on the apical half. In back of the above projection is a small, sharp pointed, tooth-like projection, yellow at the base and reddish-brown at the apex; near the middle of the upper side is a small ridge reaching to the apex.

Thorax.--Near the base of the first abdominal segment, across the middle of the next four segments and at the apex of the last segment, yellowish brown.

The humeral spiracle is small, reniform, pale yellow, smooth and slightly raised, with a row of uniform dark dots around the curved edge. (See drawing, Plate XVIII, fig. b). On the upper edge of the wing-pad is a rounded, raised surface, with a small, narrow, darkened sharp edge just back of the center. At the lower edge of the pleura and touching the wing-pad is a foot-like projection, which is reddish-brown towards the apex where there are two small, tooth-like points and one large point near the base.

The wing-pads reach to the middle of the second abdominal segment and the leg-sheaths to the middle of the third segment.

Abdomen.--There are eight well-defined segments. All but the last have a transverse row of sharp claw-like dark-brown spines across the dorsum of the segments, becoming quite long and yellow on the sides of the segments and dimishing in length on the venter. These ventral bristles increase in length, on each segment, as they near the last segment. For the location of these spines and bristles see drawing (fig. 2).

At the apex of the abdomen are four large, very rugose, reddish-brown, chitinous tooth-like spurs; between the lower pair on the dorsum, are two [p. 152] small, rounded brown tubercles. Below these tubercles, on the dorsum is a small, rounded, frosted area.

About half way between this area and the base of the segment is a large, sharp, claw-like, dark spine; at the base of this is a smaller, dark spine with two points at the apex. Between these spines and the segmental line is another sharp spine, near the base of which is a small, rounded, roughened, dark spot, which is the remains of the large posterior spiracle.

On the ventral side of the last segment are two very large tubercles, semi-transparent and darkened on the inner edge to the apex.

The under side of the thorax has two short, robust, claw-like spines, bifurcated at the apex and each having a short yellow spine, near the middle of the inner side. These spines are yellow with a reddish-brown edge.

On the side of all the segments, except the last, and close to the cephalic edge, is a reniform spiracle, it is like the humeral one except the curved side is on the opposite side.

The adult emegres through a longitudinal, dorsal slit, in the thorax and bursting of the sutures of the head.

[on p. 157]


Fig. 1. Dasyllis thoracicia Fabr., larva.
Fig. a. Dasyllis thoracica, anterior spiracle.
Fig. 2. Dasyllis thoracica, pupa.
Fig. b. Dasyllis thoracica, lateral spiracle of pupa.
Fig. 3. Dasyllis thoracica, pupa, lateral view.
Fig. 4. Dasyllis thoracica, mouth parts, ventral view.
Fig. 5. Dasyllis thoracica, mouth parts, dorsal view.

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