To the first of these questions we may answer briefly, the spread of the population has brought these irruptions more into notice than formerly, and from this cause they appear more frequent. But this does not fully account for all the facts, and therefore we must suppose that a succession of similar climatic conditions has caused more frequent migrations; and that with the changes in this respect there will be a corresponding change in the effect. In answer to the other questions, we may state that unless there should be a remarkable permanent change in the climate, we need have no fears of such results.

ART. XXII.-ON THE HEMIPTERA COLLECTED BY DR. ELLIOTT COUES, U. S. A., IN DAKOTA AND MONTANA, DURING 1873-74.*

By P. R. UHLER.

HETEROPTERA.

CORIMELÆNIDE.

1. Corimelæna pulicaria.

CORIMELÆNA, White.

Odontoscelis pulicarius, GERMAR, Zeits. vol. i, p. 39, No. 6.

Inhabits Dakota, and is found to be widely distributed throughout Eastern North America, from near Quebec to as far south as Galveston, Tex.

Scutellera æneifrons, SAY, Long's Exped. Appendix, p. 229, No. 2.

Obtained near Pembina, Dak., and from the vicinity of Mouse River, August 29, 1873.

Subfamily EURYGASTRINA.

3. Eurygaster alternatus.

EURYGASTER, Lap.

Tetyra alternata, SAY, Amer. Entomology, vol. i, p. 43, tab. 3, fig. 3.

Collected from the prairies near Mouse River, August 29, from near Pembina, from Turtle Mount, Dakota, and from the Milk River region in Northern Montana.

Pentatoma cincta, PALISOT-BEAUV. Ins. Afr. et Amér. p. 114, pl. 8, fig. 7.
Cydnus lygatus, SAY, Heteropt. p. 10, No. 1.

Found near Pembina, and near Mouse River on August 29, 1873.

Pentatoma exapta, SAY, Journ. Acad. Phila. vol. iv, p. 313, No. 3. Brought from the Milk River region in 1874.

6. Perillus claudus.

Pentatoma clauda, SAY, Journ. Acad. Phila. vol. iv, p. 313, No. 3. Collected near Turtle Mount, July 24, 1873.

Inhabits the plains near Pembina, and was obtained also near Mouse River, August 29, 1873, and in the Milk River region.

Subfamily PENTATOMINA.

8. Cosmopepla carnifex.

COSMOPEPLA, Stål.

Cimex carnifex, FAB. Ent. Syst. Suppl. p. 535, No. 162.

Collected from near Pembina in June; from Turtle Mount, July 24; and from the Milk River region

CENUS, Dallas.

9. Conus delius.

Pentatoma delia, SAY, Heteropt. p. 8, No. 18.

From the vicinity of Pembina; also from Mouse River region, August 29.

10. Lioderma viridicata.

LIODERMA, Uhler.

Lioderma viridicata, UHLER, in Wheeler's Report on Nevada, Utah, &c., p. 830, pl. 42, fig. 11.

Obtained in the Milk River region, Montana.

Lygaus eurinus, SAY, Journ. Acad. Philad. vol. iv, p. 324, No. 5.

From Pembina; Turtle Mount, July 24, and from Milk River region.

12. Neides muticus.

NEIDES, Latr.

Berytus muticus, SAY, Heteropt. New Harmony, p. 13. Found in the vicinity of Pembina; date not given.

13. Harmostes reflexulus.

HARMOSTES, Burm.

Syromastes reflexulus, SAY, Heteropt. p. 10, No. 1.

From near Mouse River, August 29.

CORIZUS, Fallen.

14. Corizus lateralis.

Coreus lateralis, SAY, Journ. Acad. Philad. vol. iv, p. 320, No. 4.

Corizus lateralis, SIGNORET, Ann, Soc. Ent. France, sér. 3, vol. vii, p. 97, No. 36. Brought from Turtle Mount, July 23.

15. Corizus punctiventris.

Corizus punctiventris, DALLAS, Brit. Mus. List Hemipt. vol. ii, p. 523, No. 3.
Corizus borealis, UHLER, Proceed. Acad. Philad. 1861, p. 284.

Found in the vicinity of Pembina in June.

Lygaus reclivatus, SAY, Journ. Acad. Philad. vol. iv, p. 321.

The presence of moisture in the soil, together with suitable shelter, may be necessary for the growth of Asclepias, upon which this species lives. Although the expedition of 1873 traversed the Plains at the right season for obtaining this insect, no specimens were secured; and as the sweeping-net was constantly employed, it would certainly have been captured if present. Not until the Milk River region was reached (the next year) did specimens occur to the collector, and only then in small numbers.

17. Geocoris bullata.

GEOCORIS.

Salda bullata, SAY, Heteropt. New Harmony, p. 18, No. 2.
Obtained near Pembina in 1873.

18. Nysius angustatus.

NYSIUS, Dallas.

Nysius angustatus, UHLER, Hayden's Survey of Montana, p. 406, No. 2. From Pembina, and from near Mouse River, August 29.

TRAPEZONOTUS.

19. Trapezonotus nebulosus.

Lygaus nebulosus, FALLEN, Monog. Cim. p. 65, No. 7.
Pamera fallax, SAY, Heteropt. p. 17, No. 6.

Two specimens were captured in the Milk River country.

Bull. iv. No. 2—13