Pityogenes chalcographus L. Screening Aid

From: Cavey, J., Passoa, S. and Kucera D. 1994, Screening Aids for Exotic Bark Beetles in the Northeastern United States. NA-TP-11-94. Northeastern Area: U.S. Department of Agriculture, Forest Service.

General Appearance in a Sample. A small species, 1.6-2.9 mm, with a moderately excavated elytral declivity bearing 3 conical teeth (males) or 3 smaller teeth (females). Color either black or often bicolored, black in front and red-brown on the latter half.

Recognizing the Genus. Similar genera of small bark beetles are Pityokteines and Orthotomicus, each represented in the NER by only one species. These taxa are distinguished from the genus Pityogenes below:

Recognizing Pityogenes chalcographus. Unlike P. chalcographus which has 3 teeth, males of most North American Pityogenes have 2 teeth on the elytral declivity, e.g. P. bidentatus (Herbst), a European species established in the NER. Only P. hopkinsi Swaine, a species common throughout the region, has 3 declivital teeth on both males and females (like P. chalcographus).

The following key will help screen P. chalcographus from NER Pityogenes. Males of P. hopkinsi are very difficult to distinguish from P. chalcographus. Unfortunately, even the aedeagi are similar and difficult to study, because of their small size. The dichotomy in couplet 5 should prove useful but relative, and should be used with caution and only with identified males of the 2 species in hand for comparison.

Key to Help Screen P. chalcographus from Pityogenes
Known to Occur in the Northeastern Region.^1,2

1.	Elytral declivity with 2 teeth, teeth large with the upper pair hooked (male); or declivital teeth barely evident and head without a pit (female); P. Bidentatus	not P. chalcographus
	Elytral declivity with 3 teeth (female or male) (Fig. 4)	see #2	Figure 1. a. Pityogenes hopkinsi Swaine, and b. P. chalcographus L., female head. (a. From and b. modified from Swaine 1918).
2.	Head with a frontal pit (Fig. 1); declivital teeth small relatively inconspicuous (females)	see #3
	Head without a pit; declivital teeth conspicuous (Fig. 4) (males)	see #5	Figure 2. Pityokteines sparsus LeC., b. lateral view of female head, a. dorsal view of pronotum (from Swaine 1918).
3.	Frontal pit divided by a raised, longitudinal line (Fig. 5) distance from declivital tooth 1 to tooth 2 about ½ of that from 2 to 3 (Fig. 6); P. plagiatus female.	not chalcographus
	Frontal pit entire, not divided (Fig. 1); distance between declivital teeth 1 and 2 subequal to that between 2 and 3 (Fig. 4).	see #4	Figure 3. Abdominal apex of a. Orthotomicus caelatus (Eich.) and b. Pityogenes chalcographus L., lateral view. er = elevated ridge.
4.	Frontal pit round and small, occupying only about 1/3 of the width between the eyes (Fig. 1a).	P. hopkinsi Swaine
	Frontal pit transversely oval and large, occupying at least ½ of the width between the eyes (Fig. 1b).	P. chalcographus suspect	Figure 4. Elytral apex of male a. Pityogenes chalcographus L. and b. P. hopkinsi Swaine, oblique view.
5.	Elytral declivity with central portion between rows of teeth narrowly excavated (Fig. 4b).	P. hopkinsi Swaine
	Elytral declivity between rows of teeth widely excavated (Fig. 4a).	P. chalcographus suspect	Figure 5. Head of Pityogenes spp. showing divided frontal pit (from Swaine 1918).
1 Prepared by J.F. Cavey; character in couplet 5 provided by Dr. S.L. Wood (pers. commun. 1993). 2 Northeast species considered in writing the key were P. bidentatus, P. hopkinsi and P. plagiatus.
			Figure 6. Abdominal apex of bark beetle showing tooth 2 closer to 1 than to 3 (from Swaine 1918).

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