Pachybrachius nigriceps (Dallas)

Usinger, Robert L., 1946, Hemiptera Heteroptera of Guam, Insects of Guam II, Honolulu, Hawaii: Bernice P. Bishop Museum, Bulletin 189, pp. 11-103 : 30

25. Pachybrachius nigriceps (Dallas) .

Rhyparochromus nigriceps Dallas , List Hemipt. Brit. Mus. 2: 577, 1852.

Two specimens, Guam, Fullaway ; nine specimens, Piti Hills , June3, sweeping Styphelia, Swezey ; 32 specimens, 2 miles south of Piti, June 13, on heliotrope, Usinger ; one specimen, Piti, Nov. 22, at light, Swezey ; one specimen each, April 30, Swezey and Usinger , May 1, May 2, May 26, Piti, Usinger ; pne specimen, Tarague, May 17, on Tournefortia [ Messerschmidia ], Usinger ; one specimen, Mt. Chachao, May 16, on Styphelia, Usinger ; two specimens, Ritidian Point, June 2, on Euphorbia hirta, Usinger .

Widely distributed over the islands of the Pacific. China [Ins. Samoa 2 (3): 129, 1930] remarks that it "is somewhat variable and is probably composite." Variation is most conspicuous in the form of the anterior lobe of the pronotum. Typical examples from Hawaii vary in this respect but average nearly half as long as broad. The Guam seriesaverages two thirds as long as broad. Series from other islands, especially at the extremes of the range such as Rapa, suggest a Rassenkreis but the Guam series does not seem to be sufficiently extreme to warrant a special name at this time.

P. nigriceps was commonest on heliotrope on which eggs were laid on June 23. The eggs were deposited at the tip of a flower head amongthe small flowers. They were placed crosswise to one another and rather loosely in the open but were fastened together and to the flower calyx. They are elongate, slightly curved, about 1 mm. long by 0.35 mm. in diameter. The micropylar end is thicker, subtruncate, while the other end is tapering and rounded at the tip. The chorion is sculptured, exhibiting prominent hexagonal reticulations on the anterior (micropylar) third. Near the middle, these become inconspicuous or appear as slight rugosities. The posterior end is perfectly smooth. The whole surface is glabrous and the egg is almost water white in color. There are five small but very distinct processes forming a small ring on the surface of the micropylar end. The incubation period is six days.