Are pine caterpillars beneficial insects or pests? Feeding habits of Lepidoptera insects and treatment of stings

When people mention pine caterpillars, the impression most people have is of a dark brown insect covered all over in venomous hairs; just seeing the dense mass of venomous hairs on its body is enough to make one's skin crawl and inspire fear. So are pine caterpillars beneficial insects or pests? What do they eat? What should you do if you are stung by a pine caterpillar?

Pine caterpillar is the collective name for insects of the genus Dendrolimus in the family Lasiocampidae of the order Lepidoptera. Also known as caterpillars, fire caterpillars, and called pine silkworms in ancient times, there are more than 30 species in total, and 27 species are distributed in China, which is the country with the richest variety of pine caterpillars.

Are pine caterpillars beneficial insects or pests? What do they eat?

Pine caterpillars feed on the leaves of trees such as pines, cypresses and firs. According to statistics, 1200 pine caterpillars growing from larvae to adults can eat one large tree, making them an important forest pest of tree species such as cypresses and pines in rural areas. To this day, pine caterpillars remain the main forest pest among forest pests in terms of occurrence volume and breadth of damage.

Farmers have many methods for controlling pine caterpillars, including biological control (Beauveria bassiana, Bacillus thuringiensis, cytoplasmic polyhedrosis virus, Trichogramma, etc.), and insecticide control (1.2% nicotine-matrine smoke spraying), chemical pesticide control and silvicultural techniques and other measures.

Natural enemies of pine caterpillars

The natural enemies of pine caterpillars at each life stage number more than 300 species. Among parasitic insects, the highest parasitism rates are found in Trichogramma dendrolimi, Telenomus dendrolimusi, Anastatus japonicus, Casinaria nigripes, Aleiodes dendrolimi, Exorista civiloides, Blepharipa zebina and Carcelia matsukarehae; among predatory insects, black mountain ants and two-spined ants have the largest predation volume. Among pathogenic microorganisms there are Beauveria bassiana, cytoplasmic polyhedrosis virus and nuclear polyhedrosis virus, etc. Among birds, the common cuckoo, grey-chinned minivet, oriole, grey magpie and great tit have relatively large predation volumes.

What symptoms appear after being stung by a pine caterpillar?

1. After contact with pine caterpillar toxin, there is local pain and prickling itchiness; after about half an hour, papules, maculopapules or wheals appear at the site, and within hours to days, erythema nodosum, blisters, subcutaneous nodules or subcutaneous hematomas may be seen, accompanied by systemic symptoms of discomfort such as low fever, fatigue, headache, general malaise, low spirits and loss of appetite.

2. Within 1 to 2 weeks of poisoning, the joints are affected, with joint swelling that is hard to the touch, needle-prick or knife-cut like pain, obvious tenderness and impaired function. It often affects 1 to 2 small joints of the hands and feet, and the symptoms can resolve on their own in about 1 week. At the same time there may be local lymph node enlargement, single subcutaneous and muscle swellings on the hands and feet with unclear borders and tenderness, which soften in about 2 to 4 weeks and contain grass-green mucus; culture may reveal Pseudomonas aeruginosa.

3. Some cases present as migratory or recurrent arthritis.

4. Involvement of the ear is rare; in affected individuals the auricle thickens and is painful, or auricular chondroperichondritis may even occur.

5. After treatment and recovery, there is no joint deformity or other joint sequelae.

6. X-ray examination may show osteoporosis and moth-eaten like bone destruction. Laboratory tests show increased erythrocyte sedimentation rate (ESR), and elevated blood calcium and alkaline phosphatase.

What should you do if you are stung by a pine caterpillar?

1. Adhesive tape can be repeatedly pressed onto the affected area to pull out the venomous hairs.

2. A 1% menthol calamine lotion can be applied topically.

3. Anti-allergic drugs can control the symptoms, such as oral diphenhydramine, promethazine, chlorpheniramine, etc.; intravenous calcium gluconate may also be given; but symptoms often recur after stopping the drug, so longer continuous medication is needed.

4. Indomethacin, ibuprofen, prednisone, betamethasone and others are also effective in controlling arthritis-type damage, but they also need to be used for a longer period, otherwise recurrence is easy.

5. Secondary bacterial infection can be prevented and treated with antibiotics, but these are ineffective against the damage caused by the toxin.

6. In traditional Chinese medicine, treatment based on syndrome differentiation is mainly directed at clearing heat and removing toxins.