O. A. Johannsen and C. R. Crosby.
The Life History of Thrypticus muhlenbergiæ.
Psyche 20:164-165, 1913.

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164 Psyche [October
vein, he says: "In some species the venation mentioned is inclined to be variable in different or even in the same specimen." Another variable character is referred to in Dr. Back's key to the species as "fourth posterior cell petiolate at the base or fourth posterior cell sessile or subsessile." L. pictipes may be either sessile, subsessile or with a short petiole. L. annulatus shows a similar variation although more rarely petiolate. One specimen of L. pictipes has the discal cell open on the left wing and another has an adventitious cross-vein in the second submarginal cell of the left wing. A specimen of L. badius and another referred doubt- fully to L. incisularis, have a similar vein in the second posterior cell on the left and right wing respectively. An undetermined species has an adventitious cross-vein in each of the second poste- rior cells, and one in the second submarginal cell of the left wing. These examples are given to show possible mutations. The type of L. badius has the basal third of the wings subfuscus. This is only distinctly marked in one of the fifteen specimens. THE LIFE HISTORY OF THRYPTICUS MUHLENBER-- GIB SP. NOV. (DIPTERA).
BY 0. A. JOHANNSEN AND C. R. CROSBY.
Cornell University, Ithaca, N. Y.
On April 21, 1909, while examining some Muhlenbergia syl- vatica on the shaded bank of Cascadilla Creek near the Cornell University Campus, Ithaca, N. Y., we noted that many of the stems were broken squarely off. The tip of the cavity was plugged with frass, and in each case a slender dipterous larva was found just below the plug. A number of these larvae was taken from the straws and placed on cotton in a vial for rearing. By May 4,. pupation has taken place. An adult fly was found alive on May 29. Again on May 5, 1910, similar pupae were found in Muhlen- bergia stems that had been collected about two weeks previous. Adults emerged from this material on May 24. The flies were at first thought to be T. willistoni which they closely resemble, but subsequent study has convinced us that they are a new species. In order to get fresh material in all stages



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191 31 Joh amen and, Crodg-History of Thrypficus Muhlenbergiae 165 upon which to base our descriptions, we again visited in April of the present year, the spot where the former specimens were found. From the larvae then collected we reared three females and one male May 16-19, 1913. Nothing was learned of the eggs nor the man- ner of oviposition, but judging from the form of the ovipositor of the female it seems likely that the eggs are laid within the stem plant, probably in May, and that the larva remains thus within the stem until the time of pupation in April of the following year. Larva (fig. 1). Length, 5+ to 6 mm. Peripneustic. Very pale amber yellow, pharyngeal skeleton dark brown.
The combined head and thoracic segments
somewhat conical in shape, not differentiated. Abdomen with nine illy defined
segments, the anterior ones of greatest diameter, the intermediate longer than wide, anal segment with a prominence on the ventral side, each of the others with a ven- tral transverse band of arnbulacral setulse, each band consisting of 12 to 15 strong setulse followed by 2 or 3 rows of more minute ones. The pharyngeal skeleton (figs. 9, and 3) consists of a transverse saddle-like structure anteriorly to which is a pair t
Fig. 1.
Thrypticus muhlenbergice sp. nov.
1, larva, x 10. 2, pupa, x 12.
3, pharyngeal skeleton, side view, x 60. 4, phar- yngeal skeleton, ventral aspect, x 60.
5, wing of male, x 20.
6, hypopygium,
lateral aspect, x 150.
of 3-toothed mandibles (a), each one with an elongate supporting segment (b) and a small basal piece, and projecting caudad are six more elongate parts. Two of the dorsal pieces (c) are slender and rod-like, their caudal ends thin and wedge-shaped, between these is a thin, subtriangular piece; two of the ventral parts (d) are rod- shaped, slightly enlarged at each end, a little longer than the dorsal pieces; between these is a thin lanceolate piece (e).




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