An Important Insect of the Genus Pseudips: Pseudips mexicanus Hopkins

Jie PAN, Yang LI, Peize SHAO, Yunqing CHEN, Maoqiang FU, Hongbin ZHU, Yulin AN

1. Lianyungang Customs, Lianyungang 222042, China; 2. Nanjing Customs, Nanjing 210001, China

Abstract At present, there are three species of Pseudips known in the world, and P. mexicanus is an important one. The paper mainly introduced the taxonomic status, morphological characteristics and biological characteristics of P. mexicanus, and provided a key to P. mexicanus and its allied species. There is no distribution of P. mexicanus in China, and the results can provide the reference for further study of the insect.

Key words Pseudips; P. mexicanus; Morphological characteristics; Key; Biological characteristics

1 Introduction

In 2000, Cognato carried out taxonomic study on Scolytidae by means of morphology, biology, oviposition habit and molecular phylogeny, and established a new taxonomic system, namelyPseudips. The genus consists of three species of insects worldwide:P.mexicanus,P.concinnus,P.orientalis, which are all separated and recombined from the original genusIps[1].

Recently, Lianyungang Customs intercepted a pestP.mexicanusduring a quarantine inspection of Douglas fir from the United States. Later, it was identified asP.mexicanus, an imported quarantine pest in China, by experts of Chinese Academy of Inspection and Quarantine. It was confirmed that this species was intercepted for the first time in China. There is no distribution ofP.mexicanusin China, and the invasion can also carry fungi, which is of great harm to trees. If the pest colonizes and spreads in China, it may pose a great threat to China’s forestry resources and ecological environment. The paper mainly introduced the morphological characteristics, biological characteristics and control measures ofP.mexicanus, in order to provide some reference for quarantine identification of inspection and quarantine departments and further study of scientific research departments.

2 Taxonomic status

P.mexicanusHopkins, English name Monterey pine ips, belongs toPseudips, Scolytinae, Curculionidae.

3 Geographical distribution

The pest is mainly distributed in Arizona, Alaska, California, Colorado, Idaho, Montana, Oregon, Utah and Wyoming of the United States.

4 Hosts

P.mexicanuscan parasitize on many species of pine trees, includingPinusattenuate,P.contorta,P.cooperi,P.durangensis,P.hartwegii,P.leiophylla,P.montezumae,P.muricata,P.radiateandP.pseudostrobus.

5 Identification characteristics

5.1 Main characteristics of the genusPseudipsInternode suture of antennal club strongly anteriorly curved, not diconvoluted; inclined plane steep; wing disc with 3 pairs of teeth, tooth strongly processed, terete. Egg chambers pointed, with multiple eggs per chamber. This genus is similar to the generaOrthotomicusandIps, and can be distinguished by the key to genera.

1. Inclined plane of elytrum narrow, lateral margin with broad protuberances, obtuse rounded, with no more than 3 pairs of teeth; lower margin of inclined plane obtuse rounded, usually less than 3 mm; basal internode pieces on prosternum short, obtuse-angulate; females sometimes with a narrow furrow on facies frontalis; males with 2-3 pairs of large teeth on incline plane; mallet of antennae contracted, with 2 clear hair cracks at posterior 1/3 of end; harmful to Pinaceae; body length 1.8-3.7 mm

Pityogenes

Inclined plane of elytrum broad, with deep grooves, margin uplifted, sharp, with more than 3 pairs of teeth; body length usually greater than 3 mm

2

2. Mallet of antennae inclined at apex, hair cracks curved backward; third (lowermost) pair of teeth not located on lateral margin of inclined plane of elytrum, but moving from margin to middle; elytra ends not extended posteriorly; compound eyes normal in size; body length 2.2-4.3 mm

Orthotomicus

Mallet of antennae flat; third pair of teeth located at lateral margin or curved inward; elytra ends extended posteriorly; compound eyes small; body length 2.1-6.9 mm

3

3. Mallet of antennae flat, hair cracks moderate or distinctly bimodal; lateral margin of inclined plane of elytrum with 1-6 pairs of main teeth, third pair of teeth located at lateral margin or curved inward; elytra ends extended posteriorly and horizontally; compound eyes small, with smaller width than antennal scape; body length 2.1-6.9 mm

Ips

Internode suture of antennal club strongly anteriorly curved, not diconvoluted; wing disc with 3 pairs of teeth, tooth strongly processed, terete; inclined plane of elytrum steep; body length 3.5-5.0 mm

Pseudips

5.2 Identification characteristics ofP.mexicanusBody length 3.6-5.0 mm, 2.5× as long as width, dark reddish-brown. Forehead convex, bright; granules medium-sized, fine; granules gradually replaced by notches above eye; epistoma with a ridge or medium tumor. Mallet of antennae elliptic, internode suture conspicuous, elongated, arched, first internode suture reaching middle of mallet. Pronotum 1.03× as long as width, almost isometric, widest at base, side faintly curved; first half semicircular, rough in surface, second half bright, densely deeply punctured, pronotum long bristly on dorsal carina. Elytra 1.5× as long as width, anterior 3/4 lateral margin of elytra flat, almost parallel; puncture groove inconspicuous, punctures in grooves equal to those outside grooves; setae present in intermediate part of groove; elytra appeared about 3/4 of posterior part of wing, inclined plane of wing disc steep; lateral margin with 3 teeth, lowest teeth longer, located in sixth puncture groove, end fusiform to nearly pointed; central teeth large and located in third puncture groove, 2× as large as upper teeth, upper teeth located in second puncture groove[1-3].

P.mexicanusclosely resemblesP.concinnus, but differs by having large and sparse punctures on pronotum, rougher upper part of epistoma on forehead and accessory area of medium tumor, and larger punctures on elytra (Fig.1).

Note: A. Ips concinnus; B. I. grandicollis; C. I. paraconfusus; D. Pseudips mexicanus.

5.3 A key toP.mexicanusand its allied speciesBecauseP.mexicanusis similar to some species ofIpsin morphology, a key toP.mexicanusand its allied species, includingP.orientalis,P.concinnus,I.grandicollis,I.montanus,I.paraconfusus,I.leconteiandI.confuses, is established[4-5].

1. Body length 3.5-4.4 mm, 2.3× as long as width, dark reddish-brown to black-brown; mallet of antennae conspicuously thickened at base, internode suture arched apically; elytra 1.3× as long as width, 1.4× as long as width of pronotum; wing disc with 3 independent teeth on each side, conical; maternal gallery extended from mating chamber to left and right (in shape of eight diagrams), each chamber with 3-5 eggs

P.orientalis

Body length 3.5-5.0 mm, 2.5× as long as width, dark reddish-brown; mallet of antennae elliptic, internode suture conspicuous, elongated, arched; elytra 1.5 × as long as width, 1.03× as long as width of pronotum; wing disc with 3 independent teeth on each side, conical; maternal gallery located in cambium of phloem, embedded in bark and xylem, with 1-5 short crescent-shaped egg galleries radiated from central mating chamber, each chamber with 2-5 eggs (usually 4)

2

2. Body length 3.5-4.6 mm, punctures on pronotum small and dens; upper part of epistoma on forehead and accessory area of medium tumor smooth; punctures on elytra small

P.concinnus

Body length 3.6-5.0 mm, punctures on pronotum large and sparse; upper part of epistoma on forehead and accessory area of medium tumor rough; punctures on elytra large

3

3. Internode suture of antennal club strongly anteriorly curved, not diconvoluted; inclined plane steep; wing disc with 3 pairs of teeth, tooth strongly processed, terete; body length 3.6-5.0 mm

P.mexicanus

Mallet of antennae flat, hair cracks moderate or distinctly bimodal; elytra ends extended posteriorly and horizontally; inclined plane of elytrum with 5 pairs of teeth on each side, third pair of teeth located at lateral margin or curved inward; body length 2.1-6.9 mm

4

4. Distance from second tooth to first tooth on inclined plane conspicuously larger than that from first tooth to wing slot

5

Distance from second tooth to first tooth on inclined plane equal to or less than that from first tooth to wing slot

6

5. Male forehead with a conspicuous tubercle above middle of epistoma

I.grandicollis

Male forehead with a pair of laterally arranged tubercles above middle of epistoma

I.lecontei

6. Frontal setae few and short, body large, 4.6-5.4 mm long

I.montanus

Frontal setae many and long, body small

7

7. Midfrontal region usually with some small dark punctures, punctures on inclined plane of elytrum small, punctures large spaced, body length 3.8-4.3 mm

I.paraconfusus

Frontal surface usually without punctures, punctures on inclined plane of elytrum slightly large, punctures small spaced, body length 3.5-4.2 mm

I.confusus

6 Biological characteristics and hazards

AlthoughP.mexicanushas killed young monterey pine in the plateau of the United States, its adults usually damage weak and dying trees. The maternal gallery is located in cambium of phloem, which is embedded in bark and xylem, and radiates 1-5 short crescent-shaped egg galleries from central mating chamber, with 2-5 eggs (usually 4) each chamber. The gallery is very similar to that ofP.concinnus.

7 Route of transmission

P.mexicanushas certain migratory ability, but can only make

short distance diffusion. The long distance diffusion and colonization must be achieved by long-distance transport of logs and other goods. In the quarantine inspection at the port, it was found thatP.mexicanusspread as eggs, larvae and adults with hosts for long distance diffusion. International trade in logs increases the risk of long-distance diffusion and colonization of pests.

8 Control measures

At present, there are no specific measures for the control ofP.mexicanus, and we can learn from the control methods of other Ips or forest insect pests. For example, the common prevention measures of heat treatment, fumigation, soaking, peeling, trapping and radiation can be used. Prevention is the most important for prevention and control. Only by strictly controlling and strengthening the quarantine inspection of imported plants can reduce the risk of alien invasion to the greatest extent, so as to build a harmonious ecological environment.